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4.1 This guide, when used in conjunction with Guide D5730, provides direction to the selection of the various ASTM standards that are available for the investigation of soil, rock, the vadose zone, groundwater, and other media where the investigations have an environmental purpose and are conducted in cold regions of the world. It is intended to improve consistency of practice and to encourage rational planning of a site characterization program by providing information to assist in the design of an environmental reconnaissance or investigation plans. This guide is intended to provide information that will help reduce as much as possible the effect of site investigation operations on areas of frozen ground or permafrost and increase the safety of environmental operations in cold regions.4.2 This guide presents information and references for site characterization for environmental purposes in cold regions of the world.1.1 Understanding environmental processes that occur in soil and rock systems in cold regions of the world depends on adequate characterization of not only the physical, chemical, and biological properties of soil and rock but also the climatic factors under which they exist. Processes of interest may include, but are not limited to, surface and subsurface hydrology, contaminant mobilization, distribution, fate and transport, chemical and biological degradation of wastes, geomorphological, and ecological processes in general.1.2 This guide should be used in conjunction with Guide D5730.1.3 This guide describes special problems to be considered when planning field investigations in cold regions. The primary focus of this guide is presenting the special problems and concerns of site characterization in the cold regions of the world.1.4 Laboratory testing of soil, rock, and groundwater samples is specified by other ASTM standards that are not specifically discussed in this guide. Laboratory methods for measurement of physical properties relevant to environmental investigations are included in Guide D5730.1.5 The values stated in SI units are to be regarded as the standard.1.6 This guide emphasizes the care that must be taken by all field personnel during operations in tundra and permafrost areas of the world.1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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3.1 This guide is intended for use by individuals who investigate incidents involving carbon monoxide poisoning. If this guide is followed, the cause for the carbon monoxide poisoning incident may be determined, and corrective action may be identified to prevent future incidents.3.2 When attempting to identify the source of carbon monoxide, consider that it is produced at some level in virtually every fuel-burning engine, boiler, furnace, burner, stove or fire. All carbon-based fuels (for example, gasoline, diesel fuel, natural gas, propane, coal, wood, paper products, plastics) produce carbon monoxide as a result of incomplete combustion. When there is insufficient air for complete combustion, carbon monoxide can become a major product of combustion. In properly-operating fuel-fired combustion appliances (for example, residential furnaces and water heaters), the level of carbon monoxide produced may be as little as a hundred parts per million or less (that is, 0.01 %). In those same appliances, malfunctions can potentially result in significantly higher carbon monoxide concentrations (10 000 ppm to 100 000 ppm, or higher). Properly-operating internal combustion engines may also generate carbon monoxide concentrations on the order of 10 000 ppm or higher.3.3 Be aware of the effects of carbon monoxide on humans and pets. Carbon monoxide acts as a central nervous system depressant. With increasing dosage (combination of concentration and time of exposure) symptoms may include headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion, and may lead to death. Carbon monoxide is especially hazardous because it is colorless and odorless, providing no warning of its presence. When inhaled, carbon monoxide binds with hemoglobin in the blood, creating carboxyhemoglobin (COHb). The affinity of carbon monoxide for hemoglobin is approximately 200 times greater than the affinity of oxygen for hemoglobin. Therefore, the blood can accumulate dangerous levels of COHb, depriving the body of oxygen.3.4 Since there is the potential for investigators to become victims of elevated carbon monoxide levels themselves, extreme care should be taken to assure the safety of investigators and anyone else at risk of continuing carbon monoxide exposure. Carbon monoxide monitoring and measurement equipment is required to ensure life safety of those present, as well as to determine the cause of the problem and its solution.FIG. 1 Common Locations of Carbon Monoxide Build-Up1.1 This guide covers collection and preservation of information and physical evidence related to incidents involving the poisoning of individuals by carbon monoxide.1.2 This guide is not intended to address the medical effects of carbon monoxide exposure.1.3 This guide is not intended to be a guide for investigating carbon monoxide poisoning caused by hostile fires, or contamination in closed air systems or confined spaces. Guidance on the investigation of carbon monoxide poisonings related to fire can be found in NFPA 921.1.4 This guide is not intended for an investigation where equipment is removed from the incident site and conducted in a more controlled setting.1.5 This guide is intended to be used by a wide range of investigators, including first responders, appliance technicians and engineers.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 Concepts:  5.1.1 This guide summarizes the equipment, field procedures, and interpretation methods used for the determination of the depth, thickness and the seismic velocity of subsurface soil and rock or engineered materials, using the seismic refraction method. 5.1.2 Measurement of subsurface conditions by the seismic refraction method requires a seismic energy source, trigger cable (or radio link), geophones, geophone cable, and a seismograph (see Fig. 1). FIG. 1 Field Layout of a Twelve-Channel Seismograph Showing the Path of Direct and Refracted Seismic Waves in a Two-Layer Soil/Rock System (αc = Critical Angle) 5.1.3 The geophone(s) and the seismic source must be placed in firm contact with the soil or rock. The geophones are usually located in a line, sometimes referred to as a geophone spread. The seismic source may be a sledge hammer, a mechanical device that strikes the ground, or some other type of impulse source. Explosives are used for deeper refractors or special conditions that require greater energy. Geophones convert the ground vibrations into an electrical signal. This electrical signal is recorded and processed by the seismograph. The travel time of the seismic wave (from the source to the geophone) is determined from the seismic wave form. Fig. 2 shows a seismograph record using a single geophone. Fig. 3 shows a seismograph record using twelve geophones. FIG. 2 A Typical Seismic Waveform from a Single Geophone Note 1: Arrow marks arrival of first compressional wave. FIG. 3 Twelve-Channel Analog Seismograph Record Showing Good First Breaks Produced by an Explosive Sound Source (2) 5.1.4 The seismic energy source generates elastic waves that travel through the soil or rock from the source. When the seismic wave reaches the interface between two materials of different seismic velocities, the waves are refracted according to Snell's Law (3, 4). When the angle of incidence equals the critical angle at the interface, the refracted wave moves along the interface between two materials, transmitting energy back to the surface (Fig. 1). This interface is referred to as a refractor. 5.1.5 A number of elastic waves are produced by a seismic energy source. Because the compressional P -wave has the highest seismic velocity, it is the first wave to arrive at each geophone (see Fig. 2 and Fig. 3). 5.1.6 The P-wave velocity Vp is dependent upon the bulk modulus, the shear modulus and the density in the following manner (3): where: Vp   =   compressional wave velocity, K   =   bulk modulus, μ   =   shear modulus, and ρ   =   density. 5.1.7 The arrival of energy from the seismic source at each geophone is recorded by the seismograph (Fig. 3). The travel time (the time it takes for the seismic P-wave to travel from the seismic energy source to the geophone(s)) is determined from each waveform. The unit of time is usually milliseconds (1 ms = 0.001 s). 5.1.8 The travel times are plotted against the distance between the source and the geophone to make a time distance plot. Fig. 4 shows the source and geophone layout and the resulting idealized time distance plot for a horizontal two-layered earth. FIG. 4 (a) Seismic Raypaths and (b) Time-Distance Plot for a Two-Layer Earth With Parallel Boundaries (2) 5.1.9 The travel time of the seismic wave between the seismic energy source and a geophone(s) is a function of the distance between them, the depth of the refractor and the seismic velocities of the materials through which the wave passes. 5.1.10 The depth of a refractor is calculated using the source to geophone geometry (spacing and elevation), determining the apparent seismic velocities (which are the reciprocals of the slopes of the plotted lines in the time distance plot), and the intercept time or crossover distances on the time distance plot (see Fig. 4). Intercept time and crossover distance-depth formulas have been derived in the literature (5-4). These derivations are straightforward inasmuch as the travel time of the seismic wave is measured, the velocity in each layer is calculated from the time-distance plot, and the raypath geometry is known. These interpretation formulas are based on the following assumptions: (1) the boundaries between layers are planes that are either horizontal or dipping at a constant angle, (2) there is no land-surface relief, (3) each layer is homogeneous and isotropic, (4) the seismic velocity of the layers increases with depth, and (5) intermediate layers must be of sufficient velocity contrast, thickness and lateral extent to be detected. Reference (2) provides an excellent summary of these equations for two and three layer cases. The formulas for a two-layered case (see Fig. 4) are given below. 5.1.10.1 Intercept-time formula: where: z   =   depth of refractor two, ti   =   intercept time, V2   =   seismic velocity in layer two, and V1   =   seismic velocity in layer one. 5.1.10.2 Crossover distance formula: where: z, V2 and V1 are as defined above and xc = crossover distance. 5.1.10.3 Three to four layers are usually the most that can be resolved by seismic refraction measurements. Fig. 5 shows the source and geophone layout and the resulting time distance plot for an idealized three-layer case. FIG. 5 (a) Seismic Raypaths and (b) Time-Distance Plot for a Three-Layer Model With Parallel Boundaries (2) Note 1: While these equations are suitable for hand calculations, more advanced algorithms are used in commercially available software that is generally used to analyze seismic traces. 5.1.11 The refraction method is used to define the depth to or profile of the top of one or more refractors, or both, for example, depth of water table or bedrock. 5.1.12 The source of energy is usually located at or near each end of the geophone spread; a refraction measurement is made in each direction. These are referred to as forward and reverse measurements, sometimes incorrectly called reciprocal measurements, from which separate time distance plots are made. Fig. 6 shows the source and geophone layout and the resulting time distance plot for a dipping refractor. The velocity obtained for the refractor from either of these two measurements alone is the apparent velocity of the refractor. Both measurements are necessary to resolve the true seismic velocity and the dip of layers (2) unless other data are available that indicate a horizontal layered earth. These two apparent velocity measurements and the intercept time or crossover distance are used to calculate the true velocity, depth and dip of the refractor. Note that only two depths of the planar refractor are obtained using this approach (see Fig. 7). Depth of the refractor is obtained under each geophone by using a more sophisticated data collection and interpretation approach. FIG. 6 (a) Seismic Raypaths and (b) Time-Distance Plot for a Two-Layer Model With A Dipping Boundary (2) FIG. 7 Time Distance Plot (a) and Interpreted Seismic Section (b ) (7) 5.1.13 Most refraction surveys for geologic, engineering, hydrologic and environmental applications are carried out to determine depths of refractors that are less than 100 m (about 300 ft). However, with sufficient energy, refraction measurements can be made to depths of 300 m (1000 ft) and more (5). 5.2 Parameter Measured and Representative Values:  5.2.1 The seismic refraction method provides the velocity of compressional P-waves in subsurface materials. Although the P-wave velocity is a good indicator of the type of soil or rock, it is not a unique indicator. Table 1 shows that each type of sediment or rock has a wide range of seismic velocities, and many of these ranges overlap. While the seismic refraction technique measures the seismic velocity of seismic waves in earth materials, it is the interpreter who, based on knowledge of the local conditions and other data, must interpret the seismic refraction data and arrive at a geologically feasible solution. 5.2.2 P-wave velocities are generally greater for: 5.2.2.1 Denser rocks than lighter rocks; 5.2.2.2 Older rocks than younger rocks; 5.2.2.3 Igneous rocks than sedimentary rocks; 5.2.2.4 Solid rocks than rocks with cracks or fractures; 5.2.2.5 Unweathered rocks than weathered rocks; 5.2.2.6 Consolidated sediments than unconsolidated sediments; 5.2.2.7 Water-saturated unconsolidated sediments than dry unconsolidated sediments; and 5.2.2.8 Wet soils than dry soils. 5.3 Equipment—Geophysical equipment used for surface seismic refraction measurement includes a seismograph, geophones, geophone cable, an energy source and a trigger cable or radio link. A wide variety of seismic geophysical equipment is available and the choice of equipment for a seismic refraction survey should be made in order to meet the objectives of the survey. 5.3.1 Seismographs—A wide variety of seismographs are available from different manufacturers. They range from relatively simple, single-channel units to very sophisticated multichannel units. Most engineering seismographs sample, record and display the seismic wave digitally. 5.3.1.1 Single Channel Seismograph—A single channel seismograph is the simplest seismic refraction instrument and is normally used with a single geophone. The geophone is usually placed at a fixed location and the ground is struck with the hammer at increasing distances from the geophone. First seismic wave arrival times (Fig. 2 and Fig. 3) are identified on the instrument display of the seismic waveform. For some simple geologic conditions and small projects a single-channel unit is satisfactory. Single channel systems are also used to measure the seismic velocity of rock samples or engineered materials. 5.3.1.2 Multi-Channel Seismograph—Multi-channel seismographs use 6, 12, 24, 48 or more geophones. With a multi-channel seismograph, the seismic wave forms are recorded simultaneously for all geophones (see Fig. 3). 5.3.1.3 The simultaneous display of waveforms enables the operator to observe trends in the data and helps in making reliable picks of first arrival times. This is useful in areas that are seismically noisy and in areas with complex geologic conditions. Computer programs are available that help the interpreter pick the first arrival time. 5.3.1.4 Signal Enhancement—Signal enhancement using filtering and stacking that improve the signal to noise ratio is available in most seismographs. It is an aid when working in noisy areas or with small energy sources. Signal stacking is accomplished by adding the refracted seismic signals for a number of impacts. This process increases the signal to noise ratio by summing the amplitude of the coherent seismic signals while reducing the amplitude of the random noise by averaging. 5.3.2 Geophone and Cable:  5.3.2.1 A geophone transforms the P-wave energy into a voltage that is recorded by the seismograph. For refraction work, the frequency of the geophones varies from 8 to 14 Hz. The geophones are connected to a geophone cable that is connected to the seismograph (see Fig. 1). The geophone cable has electrical connection points (take outs) for each geophone, usually located at uniform intervals along the cable. Geophone placements are spaced from about 1 m to hundreds of meters (2 or 3 ft to hundreds of feet) apart depending upon the level of detail needed to describe the surface of the refractor and the depth of the refractor(s). The geophone intervals may be adjusted at the shot end of a cable to provide additional seismic velocity information in the shallow subsurface. 5.3.2.2 If connections between geophones and cables are not waterproof, care must be taken to assure they will not be shorted out by wet grass, rain, etc. Special waterproof geophones (marsh geophones), geophone cables and connectors are required for areas covered with shallow water. 5.3.3 Energy Sources:  5.3.3.1 The selection of seismic refraction energy sources is dependent upon the depth of investigation and geologic conditions. Four types of energy sources are commonly used in seismic refraction surveys: sledge hammers, mechanical weight drop or impact devices, projectile (gun) sources, and explosives. 5.3.3.2 For shallow depths of investigation, 5 to 10 m (15 to 30 ft), a 4 to 7 kg (10 to 15 lb) sledge hammer may be used. Three to five hammer blows using signal enhancement capabilities of the seismograph will usually be sufficient. A strike plate on the ground is used to improve the coupling of energy from the hammer to the soil. 5.3.3.3 For deeper investigations in dry and loose materials, more seismic energy is required, and a mechanized or a projectile (gun) source may be selected. Projectile sources are discharged at or below the ground surface. Mechanical seismic sources use a large weight (of about 100 to 500 lb or 45 to 225 kg) that is dropped or driven downward under power. Mechanical weight drops are usually trailer mounted because of their size. 5.3.3.4 A small amount of explosives provides a substantial increase in energy levels. Explosive charges are usually buried to reduce energy losses and for safety reasons. Burial of small amounts of explosives (less than 1 lb or 0.5 kg) at 1 to 2 m (3 to 6 ft) is effective for shallow depths of investigation (less than 300 ft or 100 m) if backfilled and tamped. For greater depths of investigation (below 300 ft or 100 m), larger explosives charges (greater than 1 lb or 0.5 kg) are required and usually are buried 2 m (6 ft) deep or more. Use of explosives requires specially-trained personnel and special procedures. 5.3.4 Timing—A timing signal at the time of impact (t = 0) is sent to the seismograph (see Fig. 1). The time of impact (t = 0) is detected with mechanical switches, piezoelectric devices or a geophone (or accelerometer), or with a signal from a blasting unit. Special seismic blasting caps should be used for accurate timing. 5.4 Limitations and Interference:  5.4.1 General Limitations Inherent to Geophysical Methods:  5.4.1.1 A fundamental limitation of all geophysical methods is that a given set of data cannot be associated with a unique set of subsurface conditions. In most situations, surface geophysical measurements alone cannot resolve all ambiguities, and some additional information, such as borehole data, is required. Because of this inherent limitation in the geophysical methods, a seismic refraction survey is not a complete assessment of subsurface conditions. Properly integrated with other geologic information, seismic refraction surveying is an effective, accurate, and cost-effective method of obtaining subsurface information. 5.4.1.2 All surface geophysical methods are inherently limited by decreasing resolution with depth. 5.4.2 Limitations Specific to the Seismic Refraction Method:  5.4.2.1 When refraction measurements are made over a layered earth, the seismic velocity of the layers are assumed to be uniform and isotropic. If actual conditions in the subsurface layers deviate significantly from this idealized model, then any interpretation also deviates from the ideal. An increasing error is introduced in the depth calculations as the angle of dip of the layer increases. The error is a function of dip angle and the velocity contrast between dipping layers (8, 9). 5.4.2.2 Another limitation inherent to seismic refraction surveys is referred to as a blind-zone problem (3, 2, 10). There must be a sufficient contrast between the seismic velocity of the overlying material and that of the refractor for the refractor to be detected. Some significant geologic or hydrogeologic boundaries have no field-measurable seismic velocity contrast across them and consequently cannot be detected with this technique. 5.4.2.3 A layer must also have a sufficient thickness in order to be detected (10). 5.4.2.4 If a layer has a seismic velocity lower than that of the layer above it (a velocity reversal), the low seismic velocity layer cannot be detected. As a result, the computed depths of deeper layers are greater than the actual depths (although the most common geologic condition is that of increasing seismic velocity with depth, there are situations in which seismic velocity reversals occur). Interpretation methods are available to address this problem in some instances (11). 5.4.3 Interferences Caused by Natural and by Cultural Conditions:  5.4.3.1 The seismic refraction method is sensitive to ground vibrations (time-variable noise) from a variety of sources. Geologic and cultural factors also produce unwanted noise. 5.4.3.2 Ambient Sources—Ambient sources of noise include any vibration of the ground due to wind, water movement (for example, waves breaking on a nearby beach), natural seismic activity, or by rainfall on the geophones. 5.4.3.3 Geologic Sources—Geologic sources of noise include unsuspected variations in travel time due to lateral and vertical variations in seismic velocity of subsurface layers (for example, the presence of large boulders within a soil). 5.4.3.4 Cultural Sources—Cultural sources of noise include vibration due to movement of the field crew, nearby vehicles, and construction equipment, aircraft, or blasting. Cultural factors such as buried structures under or near the survey line also may lead to unsuspected variations in travel time. Nearby powerlines may induce noise in long geophone cables. 5.4.3.5 During the course of designing and carrying out a refraction survey, sources of ambient, geologic, and cultural noise should be considered and its time of occurrence and location noted. The interference is not always predictable because it depends upon the magnitude of the noises and the geometry and spacing of the geophones and source. 5.5 Alternative Methods—The limitations discussed above may prevent the use of the seismic refraction method, and other geophysical or non-geophysical methods may be required to investigate subsurface conditions (see Guide D5753). 1.1 Purpose and Application—This guide covers the equipment, field procedures, and interpretation methods for the assessment of subsurface conditions using the seismic refraction method. Seismic refraction measurements as described in this guide are applicable in mapping subsurface conditions for various uses including geologic, geotechnical, hydrologic, environmental (1), mineral exploration, petroleum exploration, and archaeological investigations. The seismic refraction method is used to map geologic conditions including depth of bedrock, or the water table, stratigraphy, lithology, structure, and fractures or all of these. The calculated seismic wave velocity is related to mechanical material properties. Therefore, characterization of the material (type of rock, degree of weathering, and rippability) is made on the basis of seismic velocity and other geologic information. 1.1.1 The geotechnical industry uses English or SI units. 1.2 Limitations:  1.2.1 This guide provides an overview of the seismic refraction method using compressional (P) waves. It does not address the details of the seismic refraction theory, field procedures, or interpretation of the data. Numerous references are included for that purpose and are considered an essential part of this guide. It is recommended that the user of the seismic refraction method be familiar with the relevant material in this guide and the references cited in the text and with appropriate ASTM standards cited in 2.1. 1.2.2 This guide is limited to the commonly used approach to seismic refraction measurements made on land. The seismic refraction method can be adapted for a number of special uses, on land, within a borehole and on water. However, a discussion of these other adaptations of seismic refraction measurements is not included in this guide. 1.2.3 There are certain cases in which shear waves need to be measured to satisfy project requirements. The measurement of seismic shear waves is a subset of seismic refraction. This guide is not intended to include this topic and focuses only on P wave measurements. 1.2.4 The approaches suggested in this guide for the seismic refraction method are commonly used, widely accepted, and proven; however, other approaches or modifications to the seismic refraction method that are technically sound may be substituted. 1.2.5 Technical limitations and interferences of the seismic refraction method are discussed in D420, D653, D2845, D4428/D4428M, D5088, D5730, D5753, D6235, and D6429. 1.3 Precautions:  1.3.1 It is the responsibility of the user of this guide to follow any precautions within the equipment manufacturer's recommendations, establish appropriate health and safety practices, and consider the safety and regulatory implications when explosives are used. 1.3.2 If the method is applied at sites with hazardous materials, operations, or equipment, it is the responsibility of the user of this guide to establish appropriate safety and health practices and determine the applicability of any regulations prior to use. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this guide means only that the document has been approved through the ASTM consensus process. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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This guide specifies the format for representing and sharing information about nanomaterials, small molecules and biological specimens along with their assay characterization data using spreadsheet or TAB-delimited files. It is intended to facilitate the meaningful submission and exchange of nanomaterial descriptions and characterization data (metadata and summary data) along with the other files (raw/derived data files, image files, protocol documents, etc.) among individual researchers and to or from nanotechnology resources. It also provides researchers with guidelines for representing nanomaterials and characterizations to achieve cross-material comparison.1.1 This guide (ISA-TAB-Nano) specifies the format for representing and sharing information about nanomaterials, small molecules and biological specimens along with their assay characterization data (including metadata, and summary data) using spreadsheet or TAB-delimited files.1.2 The Appendices Sections contain a detailed listing of ISA-TAB-Nano fields (Appendix X1), a practical example (Appendix X2), a discussion of optional files (Appendix X3), and summary of background (Appendix X4).1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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5.1 Concepts: 5.1.1 All TDEM/TEM instruments are based on the concept that a time-varying magnetic field generated by a change in the current flowing in a large loop on the ground will cause current to flow in the earth below it (Fig. 3). In the typical TDEM/TEM system, these earth-induced currents are generated by abruptly terminating a steady current flowing in the transmitter loop (2). The currents induced in the earth material move downward and outward with time and, in a horizontally layered earth, the strength of the currents is directly related to the ground conductivity at that depth. These currents decay exponentially. The decay lasts microseconds, except in the cases of a highly conductive ore body or conductive layer when the decay can last up to a second. Hence, many measurements can be made in a short time period allowing the data quality to be improved by stacking.5.1.2 Most TDEM/TEM systems use a square wave transmitter current with the measurements taken during the off-time (Fig. 2) with the total measurement period of less than a minute. Because the strength of the signal depends on the induced current strength and secondary magnetic field, the depth of site investigation depends on the magnetic moment of the transmitter.5.1.3 A typical transient response, or receiver voltage measured, for a homogeneous subsurface (half-space) is shown in Fig. 4. The resistivity of the subsurface is obtained from the late stage response. If there are two horizontal layers with different resistivities, the response or receiver output voltage is similar to the curves shown in Fig. 5.5.2.8 Variations in temperature above freezing will affect resistivity measurements as a result of the temperature dependence of the resistivity of the pore fluid, which is of the order of 2 % per degree Celsius (1 % per degree Fahrenheit). Thus, data from measurements made in winter can be quite different from those made in summer.5.2.9 As the ground temperature decreases below freezing, the resistivity increases with decreasing temperature, slowly for fine materials (in which a significant portion of the water remains unfrozen, even at quite low temperatures), and rapidly for coarse materials (in which the water freezes immediately).5.2.10 Further information about factors that control the electrical resistivity or conductivity of different geological materials can be found in Ward 1990 (7).5.2.11 Because the TDEM/TEM technique measures subsurface resistivity, only geological or hydrological structures that cause spatial variations in resistivity are detected by this technique. If there is no resistivity contrast between the different geological materials or structures, if the resistivity contrast is too small to be detected by the instrument, or if the resistivity of the subsurface material is very high, the TDEM/TEM technique gives no useful information.5.3 Equipment—Geophysical equipment used for the TDEM/TEM method includes a transmitter, a transmitter loop of wire, a transmitter power supply, a receiver and one or more receiver coils.5.3.1 The transmitter may have power output ranging from a few watts to tens of kilowatts. Important parameters of the transmitter are that it transmits a clean wave-form (Fig. 2), and that the “turn-off” characteristics are well known and extremely stable, because they influence the initial shape of the transient response.5.3.2 The size of the transmitter power supply determines the depth of exploration, and can range from a few small batteries to a 10-kW, gasoline-driven generator.5.3.3 The transmitter loop wire is usually insulated for safety. The size of the loop and the amount of current flowing through it (and thus the diameter of the wire) determines the desired depth of exploration. The weight of the loop, which is generally stored on one or more reels, can be anywhere from a few kilograms to over 100 kg (from a few pounds to over 225 lb).5.3.4 The receiver measures the time-varying characteristic of the receiver coil output voltage at a number of points along the decay curve and stores this data in memory. Because the voltage is small, and changes rapidly with time, the receiver must have excellent sensitivity, noise rejection, linearity, stability, and bandwidth. The transmitter/receiver combination must have some facility for synchronization so that the receiver accurately records the time of transmitter current termination or variation. This synchronization is done either with an interconnecting timing cable or with high-stability quartz crystal oscillators mounted in each unit. The characteristics of a TDEM/TEM receiver and transmitter are sufficiently specialized that use of transmitters and receivers not specifically designed for TDEM/TEM by their manufacturers is not recommended.5.3.5 The receiver coil must match the characteristics of the receiver itself. It may contain a built-in preamplifier so that it can be located some distance from the receiver. The coil must be free from microphone noise, and it must be constructed so that the transient response from the metal of the coil and the coil shielding is negligible.5.4 Limitations and Interferences: 5.4.1 General Limitations Inherent to Geophysical Methods: 5.4.1.1 A fundamental limitation of all geophysical methods is that a given set of data cannot be associated with a unique set of subsurface conditions. In most situations, surface geophysical measurements alone cannot resolve all ambiguities, and additional information, such as borehole data, is required. Because of this inherent limitation in the geophysical methods, a TDEM/TEM survey alone is not considered a complete assessment of subsurface conditions. Properly integrated with other geologic information, TDEM/TEM surveying is a highly effective method of obtaining subsurface information.5.4.1.2 In addition, all surface geophysical methods are inherently limited by decreasing resolution with depth.5.4.2 Limitations Specific to the TDEM/TEM Method: 5.4.2.1 Subsurface layers are assumed horizontal within the area of measurement.5.4.2.2 A sufficient resistivity contrast between the background conditions and the feature being mapped must exist for the feature to be detected. Some significant geologic or hydrogeologic boundaries may have no field-measurable resistivity contrast across them and consequently cannot be detected with this technique.5.4.2.3 The TDEM/TEM method does not work well in highly resistive (very low conductivity) materials due to the difficulty in measuring low values of conductivity.5.4.2.4 An interpretation of TDEM/TEM data alone does not yield a unique correlation between possible geologic models and a single set of field data. This ambiguity can be significantly reduced by doing an equivalence analysis as discussed in 6.12.3 and can be further resolved through the use of sufficient supporting geologic data and by an experienced interpreter.5.4.3 Interferences Caused by Natural and Cultural Conditions: 5.4.3.1 The TDEM/TEM method is sensitive to noise from a variety of natural ambient and cultural sources. Spatial variations in resistivity caused by geologic factors may also produce noise. Cultural noise be manifested as very obviously erratic curve behavior such as in Fig. 7, or it may be subtle, repeatable, and difficult to distinguish from valid subsurface changes in resistivity.FIG. 7 Oscillations Induced in Receiver Response by Power Lines (5)5.4.3.2 Ambient Sources of Noise—Ambient sources of noise include radiated and induced responses from nearby metallic structures, and soil and rock electrochemical effects, including induced polarization. In TDEM/TEM soundings, the signal-to-noise ratio (SNR) is usually good over most of the measurement time range. However, at late times, the transient response from the ground decays extremely rapidly such that, towards the end of the transient, the signal deteriorates completely and the data become extremely noisy.5.4.3.3 Radiated and Induced Noise—Radiated noise consists of signals generated by radio, radar transmitters, and lightning. The first two are not generally a problem. However, on summer days when there is extensive local thunderstorm activity, the electrical noise from lightning strikes can cause noise problems. It may be necessary to increase the integration (stacking) time or, in severe cases, to discontinue the survey until the storms have passed by or abated.(1) The most important source of induced noise consists of intense magnetic fields arising from 50/60 Hz power lines. The large signals induced in the receiver from this source (the strength of which falls off more or less linearly with distance from the power line) can overload the receiver if the receiver gain is set too high, causing serious errors. The remedy is to reduce receiver gain to the point that overload does not occur. In some cases, this may result in less accurate measurement of the transient because the available dynamic range of the receiver is not fully utilized. Another alternative is to move the measurement array (particularly the receiver coil) further from the power line. The equipment manufacturer’s documentation may also provide information about which repetition rates or base frequencies (if any) provide the best rejection of the noise arising from power lines.(2) It was mentioned above that one of the advantages of TDEM/TEM resistivity sounding was that measurement of the transient signal from the ground was made in the absence of the primary transmitter field, since measurement is made after transmitter current turnoff (Fig. 2). Modern transmitters use extremely effective electronic switches to terminate the large transmitter current. Nevertheless very sensitive receivers can still detect small currents that linger in the loop after turn-off. The magnitude of these currents and their time behavior are available from the equipment manufacturer, who can advise the user as to how closely the receiver coil can be placed to the actual transmitter loop wire.(3) Another source of induced noise, common to ferrite or iron-cored receiver coils, is microphone noise arising from minute movements of the receiver coil in the earth's relatively strong magnetic field. Such movements are usually caused by the wind, and the coil must be shielded from the wind noise, or the measurements made at night when this source of noise is minimal. In extreme cases, it may be necessary to bury the coil.5.4.3.4 Presence of Nearby Metallic Structures—TDEM/TEM systems are excellent metal detectors. Use of such systems for resistivity sounding demands that measurements are not made in the presence of metal. This requires removal of all metallic objects not part of the survey equipment (metallic chairs, toolboxes, etc.) from the area of the survey instruments. The recommendations of the manufacturer with regard to the location of the receiver case itself with respect to the receiver coil must be followed carefully.(1) Power lines can often be detected as metallic targets as well as sources of induced noise. In this case, they exhibit an oscillatory response (the response from all other targets, including the earth, decays monotonically to zero without oscillation). Because the frequency of the oscillation is unrelated to the receiver base frequency, the effect of power line metallic response is to render the transient “noisy” (Fig. 7). Because these oscillations arise from response to eddy currents induced in the power line by the TDEM/TEM transmitter, repeating the measurement produces an identical response, which is one way that these oscillators are identified. Another way is to take a measurement with the transmitter turned off. If the noise disappears, it is a good indication that power line response is the problem. The only remedy is to move the transmitter loop further from the power line.(2) Other metallic responses, such as those from buried metallic trash or pipes can present a problem. If the response is large, another sounding site must be selected. Use of a different geophysical instrument such as a metal detector or ground conductivity meter is helpful to quickly survey the sounding site for buried metal.5.4.3.5 Geologic Sources of Noise—Geologic noise arises from the presence of unsuspected geological structures or materials, which cause variations in terrain resistivity. A rare effect that can occur in clayey soils, is induced polarization. Rapid termination of the transmitter current and thus primary magnetic field can charge up small electrical capacitors at soil particle interfaces. These capacitors subsequently discharge, producing current flow similar to that shown in Fig. 3, but reversed in direction. The net effect is to reduce the amplitude of the transient response (thus increasing the apparent resistivity) or, in severe situations, to cause the transient response to become negative over some portion of the measurement time range. Because these sources of reverse current are most significant in the vicinity of the transmitter loop, using the offset configuration (described in 6.7.1.1) usually reduces the induced polarization effect.5.5 Summary—During the course of designing and carrying out a TDEM/TEM survey, the sources of ambient, geologic and cultural noise must be considered and the time of occurrence and location noted. The form of the interference is not always predictable, as it not only depends upon the type of noise and the magnitude of the noise but upon the distance from the source of noise and possibly the time of day.5.6 Alternate Methods—In some cases, the factors discussed above may prevent the effective use of the TDEM/TEM method, and other surface geophysical methods such as conventional direct current (DC) resistivity sounding (Guide D6431), frequency domain electromagnetic surveying (Guide D6639) or non-geophysical methods may be required to investigate subsurface conditions.1.1 Purpose and Application: 1.1.1 This guide is one in a series of documents that describe geophysical site investigation methods.1.1.2 This guide summarizes the equipment, field procedures, and interpretation methods for the assessment of subsurface materials and their pore fluids using the Time Domain Electromagnetic (TDEM) method. This method is also known as the Transient Electromagnetic (TEM) Method, and in this guide is referred to as the TDEM/TEM method. Time Domain and Transient refer to the measurement of a time-varying induced electromagnetic field.1.1.3 The TDEM/TEM method is applicable to the subsurface site investigation for a wide range of conditions. TDEM/TEM methods measure variations in the electrical resistivity (or the reciprocal, the electrical conductivity) of the subsurface soil or rock caused by both lateral and vertical variations in various physical properties of the soil or rock. By measuring both lateral and vertical changes in resistivity, variations in subsurface conditions can be determined.1.1.4 Electromagnetic measurements of resistivity as described in this guide are applied in geologic studies, geotechnical studies, hydrologic site investigations, and for mapping subsurface conditions at waste disposal sites (1).2 Resistivity measurements can be used to map geologic changes such as lithology, geological structure, fractures, stratigraphy, and depth to bedrock. In addition, measurement of resistivity can be applied to hydrologic site investigations such as the depth to water table, depth to aquitard, presence of coastal or inland groundwater salinity, and for the direct exploration for groundwater.1.1.5 This standard does not address the use of TDEM/TEM method for use as metal detectors or their use in unexploded ordnance (UXO) detection and characterization. While many of the principles apply the data acquisition and interpretation differ from those set forth in this standard guide.1.1.6 General references for the use of the method are McNeill (2), Kearey and Brooks (3), and Telford et al (4).1.2 Limitations: 1.2.1 This guide provides an overview of the TDEM/TEM method. It does not provide or address the details of the theory, field procedures, or interpretation of the data. Numerous references are included for that purpose and are considered an essential part of this guide. It is recommended that the user of the TDEM/TEM method be familiar with the references cited and with the ASTM standards D420, D653, D5088, D5608, D5730, D5753, D6235, D6429 and D6431.1.2.2 This guide is limited to TDEM/TEM measurements made on land. The TDEM/TEM method can be adapted for a number of special uses on land, water, ice, within a borehole, and airborne. Special TDEM/TEM configurations are used for metal and unexploded ordnance detection. These TDEM/TEM methods are not discussed in this guide.1.2.3 The approaches suggested in this guide for the TDEM/TEM method are commonly used, widely accepted, and proven. However, other approaches or modifications to the TDEM/TEM method that are technically sound may be substituted.1.2.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education, experience, and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word standard in the title of this document means only that the document has been approved through the ASTM consensus process.1.3 Precautions: 1.3.1 It is the responsibility of the user of this guide to follow any precautions in the equipment manufacturer's recommendations and to establish appropriate health and safety practices.1.3.2 If the method is used at sites with hazardous materials, operations, or equipment, it is the responsibility of the user of this guide to establish appropriate safety and health practices and to determine the applicability of any regulations prior to use.1.3.3 This guide does not purport to address all of the safety concerns that may be associated with the use of the TDEM/TEM method. It must be emphasized that potentially lethal voltages exist at the output terminals of many TDEM/TEM transmitters, and also across the transmitter loop, which is sometimes uninsulated. It is the responsibility of the user of this equipment to assess potential environmental safety hazards resulting from the use of the selected equipment, establish appropriate safety practices and to determine the applicability of regulations prior to use.1.3.4 Units—The values stated in SI units are regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units, which are provided for information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this guide.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 Concepts: 5.1.1 This guide summarizes the basic equipment, field procedures, and interpretation methods used for detecting, delineating, or mapping shallow subsurface features and relative changes in layer geometry or stratigraphy using the seismic-reflection method. Common applications of the method include mapping the top of bedrock, delineating bed or layer geometries, identifying changes in subsurface material properties, detecting voids or fracture zones, mapping faults, defining the top of the water table, mapping confining layers, and estimating of elastic-wave velocity in subsurface materials. Personnel requirements are as discussed in Practice D3740.5.1.2 Subsurface measurements using the seismic-reflection method require a seismic source, multiple seismic sensors, multi-channel seismograph, and appropriate connections (radio or hardwire) between each (Fig. 1, also showing optional roll-along switch).Seismic energy propagation time between seismic sensors depends on wave type, travel path, and seismic velocity of the material. The travel path of reflected body waves (compressional (P) and shear (S) waves) is controlled by subsurface material velocity and geometry of interfaces defined by acoustic impedance (product of velocity and density) changes. A difference in acoustic impedance between two layers results in an impedance contrast across the boundary separating the layers and determines the reflectivity (reflection coefficient) of the boundary; for example, how much energy is reflected versus how much is transmitted (Eq 3). At normal incidence:where:R   =   reflectivity = reflection coefficient,V1V2   =   velocity of layers 1 and 2,ρ1ρ2   =   density of layers 1 and 2,Vρ   =   acoustic impedance, andA   =   impedance contrast.Snell’s law (Eq 4) describes the relationship between incident, refracted, and reflected seismic waves:where:i   =   incident angle,r   =   reflected angle, andt   =   refracted angle.At each boundary represented by a change in the product of velocity and density (acoustic impedance), the incident seismic wave generates a reflected P, reflected S, transmitted P, and transmitted S wave. This process is described by the Zoeppritz equations (for example, Telford et al. (4)).5.1.3.2 Analysis and recognition of seismic energy arrival patterns at different seismic sensors allows estimation of depths to reflection coefficients (reflectors) and average velocity between the reflection coefficient and the earth’s surface. Analog display of the seismic waves recorded by each seismic sensor is generally in wiggle trace format on the seismogram (Fig. 2) and represents the particle motion (velocity or acceleration) consistent with the orientation and type of the seismic sensor (geophone or accelerometer) and source.(A) Velocities are mean for a range appropriate for the material (5).(B) Acoustic impedance is velocity multiplied by density, specifically for compressional waves; the equivalent for shear waves is referred to as seismic impedance (units of kg/s·m 2).(C) Subsonic velocities have been reported by researchers studying the ultra-shallow near surface .(A) Layer 1 on Fig. 1.(B) Layer 2 on Fig. 1.(C) R in Eq 3, Absolute value R = 1 total reflectance.5.2.1 The seismic-reflection method images changes in the acoustic (seismic) impedance of subsurface layers and features, which represent changes in subsurface material properties. While the seismic reflection technique depends on the existence of non-zero reflection coefficients, it is the interpreter who, based on knowledge of the local conditions and other data, must interpret the seismic-reflection data and arrive at a geologically feasible solution. Changes in reflected waveform can be indicative of changes in the subsurface such as lithology (rock or soil type), rock consistency (that is, fractured, weathered, competent), saturation (fluid or gas content), porosity, geologic structure (geometric distortion), or density (compaction).5.2.2 Reflection Coefficient or Reflectivity—Reflectivity is a measure of energy expected to return from a boundary (interface) between materials with different acoustic impedance values. Materials with larger acoustic impedances overlying materials with smaller acoustic impedances will result in a negative reflectivity and an associated phase reversal of the reflected wavelet. Intuitively, wavelet polarity follows reflection coefficients that are negative when faster or denser layers overlie slower or less dense (for example, clay over dry sand) layers and positive when slower or less dense layers overlie faster or denser (for example, gravel over limestone) layers. A reflectivity of one means all energy will be reflected at the interface.5.3 Equipment—Geophysical equipment used for surface seismic measurement can be divided into three general categories: source, seismic sensors, and seismograph. Sources generate seismic waves that propagate through the ground as either an impulsive or a coded wavetrain. Seismic sensors can measure changes in acceleration, velocity, displacement, or pressure. Seismographs measure, convert, and save the electric signal from the seismic sensors by conditioning the analog signal and then converting the analog signal to a digital format (A/D). These digital data are stored in a predetermined standardized format. A wide variety of seismic surveying equipment is available and the choice of equipment for a seismic reflection survey should be made to meet the objectives of the survey.5.3.1 Sources—Seismic sources come in two basic types: impulsive and coded. Impulsive sources transfer all their energy (potential, kinetic, chemical, or some combination) to the earth instantaneously (that is, usually in less than a few milliseconds). Impulsive source types include explosives, weight drops, and projectiles. Coded sources deliver their energy over a given time interval in a predetermined fashion (swept frequency or impulse modulated as a function of time). Source energy characteristics are highly dependent on near-surface conditions and source type (6-9). Consistent, broad bandwidth source energy performance is important in seismic reflection surveying. The primary measure of source effectiveness is the measure of signal-to-noise ratio and resolution potential as estimated from the recorded signal.5.3.1.1 Selection of the seismic source should be based upon the objectives of the survey, site surface and geologic conditions and limitations, survey economics, source repeatability, previous source performance, total energy and bandwidth possible at survey site (based on previous studies or site specific experiments), and safety.5.3.1.2 Coded seismic sources will generally not disturb the environment as much as impulsive sources for a given total amount of seismic energy. Variable amplitude background noise (such as passing cars, airplanes, pedestrian traffic, etc.) affects the quality of data collected with coded sources less than for impulsive sources. Coded sources require an extra processing step to compress the time-variable signal wavetrain down to a more readily interpretable pulse equivalent. This is generally done using correlation or shift and stack techniques.5.3.1.3 In most settings, buried small explosive charges will result in higher frequency and broader bandwidth data, in comparison to surface sources. However, explosive sources generally come with use restrictions, regulations, and more safety considerations than other sources. Most explosive and projectile sources are designed to be invasive, while weight drop and most coded sources are generally in direct contact with the ground surface and therefore are non-invasive.5.3.1.4 Sources that shake, impact, or drive the ground so that the dominant particle motion is horizontal to the surface of the ground are shear-wave sources. Sources that shake, impact, or drive the ground so that the dominant particle motion is vertical to the surface of the ground are compressional sources. Many sources can be used for generating both shear and compressional wave energy.5.3.2 Seismic Sensors—Seismic sensors convert mechanical particle motion to electric signals. There are three different types of seismic sensors: accelerometers, geophones (occasionally referred to as seismometers), and hydrophones.5.3.2.1 Accelerometers are devices that measure particle acceleration. Accelerometers generally require pre-amplifiers to condition signal prior to transmission to the seismograph. Accelerometers generally have a broader bandwidth of sensitivity and a greater tolerance for high G-forces than geophones or hydrophones. Accelerometers have a preferred direction of sensitivity.5.3.2.2 Geophones consist of a stationary cylindrical magnet surrounded by a coil of wire that is attached to springs and free to move relative to the magnet. Geophones measure particle velocity and therefore produce a signal that is the derivative of the acceleration measured by accelerometers. Geophones are generally robust, durable, and have unique response characteristics proportional to their natural frequency and coil impedance. The natural frequency is related to the spring constant and the coil impedance is a function of the number of wire windings in the coil.5.3.2.3 Hydrophones are used when measuring seismic signals propagating in liquids. Because shear waves are not transmitted through water, hydrophones only respond to compressional waves. However, shear waves can be converted to compressional waves at the water/earth interface and provide an indirect measurement of shear waves. Hydrophones are pressure-sensitive devices that are usually constructed of one or more piezoelectric elements that distort with pressure.5.3.2.4 Geophones and accelerometers can be used for compressional or shear wave surveys on land. Orientation of the seismic sensor determines the seismic sensor response and sensitivity to different particle motion. Some seismic sensors are omnidirectional and are sensitive to particle motion parallel to the motion axis of the sensor, regardless of the sensor’s spatial orientation direction. Others seismic sensors are designed to be used in one orientation or the other (P or S). Shear wave seismic sensors are sensitive to particle motion perpendicular to the direction of propagation (line between source and seismic sensors) and are sensitive to vertical (SV) or horizontal (SH) transverse wave motion. Compressional wave seismic sensors are sensitive to particle motion parallel to the direction of propagation (line between source and seismic sensor) and thus the motion axis of the seismic sensor needs to be in a vertical position.5.3.3 Seismographs—Seismographs measure the voltages generated by seismic sensors as a function of time and synchronize them with the seismic source. Seismographs have differing numbers of channels and a range of electronic specifications. The choice of an appropriate seismograph should be based on survey objectives. Modern multichannel seismographs are computer based and require minimal fine-tuning to adjust for differences or changes in site characteristics. Adjustable seismograph acquisition settings that will affect the accuracy or quality of recorded data are generally limited to sampling rate, record length, analog filter settings, pre-amplifier gains, and number of recording channels. There is limited need for selectable analog filters and gain adjustments with modern, large dynamic range (>16 bits) seismographs. Seismographs store digital data in standard formats (for example, SEGY, SEGD, SEG2) that are generally dependent on the type of storage medium and the primary design application of the system. Seismographs can be single units (centralized), with all recording channels (specifically analog circuitry and A/D converters) at a single location, or several autonomous seismographs can be distributed around the survey area. Distributed seismographs are characterized by several small decentralized digitizing modules (1–24 channels each) located close to the geophones to reduce signal loss over long-cable seismic sensors. Digital data from each distributed module are transmitted to a central system where data from multiple distributed units are collected, cataloged, and stored.5.3.4 Source and Seismic Sensor Coupling—The seismic sensors and sources must be coupled to the ground. Depending on ground conditions and source and seismic sensor configuration, this coupling can range from simply resting on the ground surface (for example, land streamers, weight drop, vibrator) to invasive ground penetration or burial (for example, spike, buried explosives, projectile delivery at bottom of a hole). Hydrophones couple to the ground through submersion in water in a lake, stream, borehole, ditch, etc.5.3.5 Supporting Components—Additional equipment includes a roll-along switch, cables, time-break system (radio or hardwire telemetry between seismograph and source), quality control (QC) and troubleshooting equipment (seismic sensor continuity, earth leakage, cable leakage, seismograph distortion and noise thresholds, cable and seismic sensor shorting plug), and land surveying equipment.5.4 Limitations and Interferences: 5.4.1 General Limitations Inherent to Geophysical Methods: 5.4.1.1 A fundamental limitation of all geophysical methods is that a given set of data does not uniquely represent a set of subsurface conditions. Geophysical measurements alone cannot uniquely resolve all ambiguities, and some additional information, such as borehole measurements, is required. Because of this inherent limitation in geophysical methods, a seismic-reflection survey will not completely represent subsurface geological conditions. Properly integrated with other geologic information, seismic-reflection surveying can be an effective, accurate, and cost-effective method of obtaining detailed subsurface information. All geophysical surveys measure physical properties of the earth (for example, velocity, conductivity, density, susceptibility) but require correlation to the geology and hydrology of a site. Reflection surveys do not directly measure material-specific characteristics (such as color, texture, and grain size), or lithologies (such as limestone, shale, sandstone, basalt, or schist), except to the extent that these lithologies may have different velocities and densities.5.4.1.2 All surface geophysical methods are inherently limited by signal attenuation and decreasing resolution with depth.5.4.2 Limitations Specific to the Seismic-Reflection Method: 5.4.2.1 Theoretical limitations of the seismic-reflection method are related to the presence of a non-zero reflection coefficient, seismic energy characteristics, seismic properties (velocity and attenuation), and layer geometries relative to recording geometries. In a homogenous earth, no reflections are produced and therefore none can be recorded. When reflection measurements are made at the surface of the earth, reflections can only be returned from within the earth if layers with non-zero reflection coefficients are present within the earth. Layers, for example, defined by changes in lithology without measurable changes in either velocity or density cannot be imaged with the seismic reflection method. Theoretical limits on bed or object-resolving capabilities of a seismic data set are related to frequency content of the reflected energy (see 8.4).5.4.2.2 Successful imaging of geologic layers dipping at greater than 45 degrees may require non-standard deployments of sources and seismic sensors.5.4.2.3 Resolution (discussed in 8.4) and signal-to-noise ratios are critical factors in determining the practical limitations of the seismic-reflection method. Source configuration, source and seismic sensor coupling, near-surface materials, specification of the recording systems, relative amplitude of seismic events, and arrival geometry of coherent source-generated seismic noise are all factors in defining the practical limitations of seismic-reflection method.(1) Highly attenuative near-surface materials such as dry sand and gravel, can adversely affect the resolution potential and signal strength with depth of seismic energy (10). Attenuation is rapid reduction of seismic energy as it propagates through an earth material, usually most pronounced at high frequencies. Attenuative materials can prevent survey objectives from being met.(2) While it is possible to enhance signal not visible on raw field data, it is safest to track all coherent events on processed seismic reflection sections from raw field data through all processing steps to CMP stack. Noise can be processed to appear coherent on CMP stacked sections.(3) Differences in water quality do not appear to change the velocity and density sufficiently that they can be detected by the seismic-reflection method (11).5.4.3 Interferences Caused by Natural and by Cultural Conditions: 5.4.3.1 The seismic-reflection method is sensitive to mechanical and electrical noise from a variety of sources. Biologic, geologic, atmospheric, and cultural factors can all produce noise.(1) Biologic Sources—Biologic sources of noise include vibrations from animals both on the ground surface and underground in burrows as well as trees, weeds, and grasses shaking from wind. Examples of animals that can cause noise include mice, lizards, cattle, horses, dogs, and birds. Animals, especially livestock, can produce seismic vibrations several orders of magnitude greater than seismic signals at longer offset traces on high-resolution data.(2) Geologic Sources—Geologic sources of noise include rockslides, earthquakes, scattered energy from fractures, faults or other discontinuities, and moving water (for example, water falls, river rapids, water cascading in wells).(3) Atmospheric Sources—Atmospheric sources of noise include wind shaking seismic sensors or cables, lightning, rain falling on seismic sensors, snow accumulations melting and falling from trees and roofs, and wind shaking surface structures (for example, buildings, poles, signs).(4) Cultural Sources—Cultural sources of noise include power lines (that is, 50 Hz, 60 Hz, and related harmonics), vehicles (for example, cars, motorcycles, trains, planes, helicopters, ATVs), air conditioners, lawn mowers, small engine-powered tools, construction equipment, and people—both crew members and pedestrians—moving in proximity to the seismic line. Radio Frequency (RF) and other electromagnetic (EM) signals transmitted from radar installations, radio transmitters, or beacons can appear on seismic data at amplitudes several times larger than source-generated seismic signals.5.4.3.2 During the design and operation of a seismic reflection survey, sources of biologic, geologic, atmospheric, and cultural noise and their proximity to the survey area should be considered, especially the characteristic of the noise and size of the area affected by the noise. The interference of each is not always predictable because of unknowns associated with earth coupling and energy attenuation.5.4.4 Interference Caused by Source-Generated Noise: 5.4.4.1 Seismic sources generate both signal and noise. Signal is any energy that is to be used to interpret subsurface conditions. Noise is any recorded energy that is not used to interpret subsurface conditions or diminishes the interpretability of signal. Ground roll (surface waves), direct waves, refractions, diffractions, air-coupled waves, and reflection multiples are all common types of source-generated noise observed on a seismogram recorded during seismic reflection profiling (Fig. 3).FIG. 3 Gained Field Records from Two Different Positions on One Seismic LineNOTE 1: The reflection arrivals are shown on both records.(1) Ground Roll—Ground roll is a type of surface wave that appears on a reflection seismogram (see Figs. 2 and 3). Ground roll is generated by the source and propagates along the ground surface as a lower velocity, higher amplitude, dispersive wave. Ground roll can dominate near-offset seismic sensors, making separation of reflections at close offsets difficult. Ground roll can be misinterpreted as reflection arrivals, especially if the incorrect offsets or geophone interval are used.(2) Direct Waves—The seismic energy arriving first in time at the sensors closest to the source is known as the direct wave. Direct waves are body waves that travel directly from the source seismic sensor through the uppermost layer of the earth.(3) Refractions—Refracted seismic energy travels along a velocity contrast (contact separating two different materials) returning to the surface at an angle related to the velocity above and below the contrast and with a linear phase velocity equal to the seismic velocity of the material below the velocity contrast. Refractions are generally the first (in time) coherent seismic energy to arrive at a sensor, beginning a source-to-sensor offset beyond those where direct wave energy arrives first. For a more detailed discussion of refractions and their use as a geophysical imaging tool, see Guide D5777.(4) Diffraction—Diffractions are energy scattered from discontinuous subsurface layers (faults, fractures) or points where subsurface layers or objects terminate (lens, channel, boulder). Diffractions are generally considered seismic noise when undertaking a reflection survey.(5) Air-coupled Waves—Air-coupled waves are sound waves traveling through the air, exciting the ground near the seismic sensor and then recorded by the seismic sensor. Air waves generated by the source arrive on seismograms with a linear velocity (distance from source¸ arrival time) of ~330 m/s (velocity of sound in air). Cultural noise generated by aircraft is a form of air-coupled wave. Air-coupled waves can reflect from surface objects and in some cases appear very similar to reflections from layers within the earth on seismograms. Air-coupled waves can alias to produce false trace-to-trace coherency and be misinterpreted as reflections.(6) Reflection Multiples—Reflection multiples are reflections that reverberate between several layers in the subsurface. Multiple reflections or reverberations between layers are reflections and therefore appear on seismograms with all the characteristics of reflections. Multiples can best be distinguished by their arrival pattern and cyclic nature on seismograms and their lower than expected normal move-out velocity.5.5 Alternative Methods—Limitations discussed above may preclude the use of the seismic-reflection method. Other geophysical (see Guide D6429) or non-geophysical methods may be required to investigate subsurface conditions when signal-to-noise ratio is too low or the resolution potential is insufficient for the survey objectives.1.1 Purpose and Application: 1.1.1 This guide summarizes the technique, equipment, field procedures, data processing, and interpretation methods for the assessment of shallow subsurface conditions using the seismic-reflection method.1.1.2 Seismic reflection measurements as described in this guide are applicable in mapping shallow subsurface conditions for various uses including geologic (1), geotechnical, hydrogeologic (2), and environmental (3).2 The seismic-reflection method is used to map, detect, and delineate geologic conditions including the bedrock surface, confining layers (aquitards), faults, lithologic stratigraphy, voids, water table, fracture systems, and layer geometry (folds). The primary application of the seismic-reflection method is the mapping of lateral continuity of lithologic units and, in general, detection of change in acoustic properties in the subsurface.1.1.3 This guide will focus on the seismic-reflection method as it is applied to the near surface. Near-surface seismic reflection applications are based on the same principles as those used for deeper seismic reflection surveying, but accepted practices can differ in several respects. Near-surface seismic-reflection data are generally high-resolution (dominant frequency above 80 Hz) and image depths from around 6 m to as much as several hundred meters. Investigations shallower than 6 m have occasionally been undertaken, but these should be considered experimental.1.2 Limitations: 1.2.1 This guide provides an overview of the shallow seismic-reflection method, but it does not address the details of seismic theory, field procedures, data processing, or interpretation of the data. Numerous references are included for that purpose and are considered an essential part of this guide. It is recommended that the user of the seismic-reflection method be familiar with the relevant material in this guide, the references cited in the text, and Guides D420, D653, D2845, D4428/D4428M, Practice D5088, Guides D5608, D5730, D5753, D6235, and D6429.1.2.2 This guide is limited to two-dimensional (2-D) shallow seismic-reflection measurements made on land. The seismic-reflection method can be adapted for a wide variety of special uses: on land, within a borehole, on water, and in three dimensions (3-D). However, a discussion of these specialized adaptations of reflection measurements is not included in this guide.1.2.3 This guide provides information to help understand the concepts and application of the seismic-reflection method to a wide range of geotechnical, engineering, and groundwater problems.1.2.4 The approaches suggested in this guide for the seismic-reflection method are commonly used, widely accepted, and proven; however, other approaches or modifications to the seismic-reflection method that are technically sound may be equally suited.1.2.5 Technical limitations of the seismic-reflection method are discussed in 5.4.1.2.6 This guide discusses both compressional (P) and shear (S) wave reflection methods. Where applicable, the distinctions between the two methods will be pointed out in this guide.1.3 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration for a project’s many unique aspects. The word “Standard” in the title of this guide means only that the document has been approved through the ASTM consensus process.1.4 The values stated in SI units are regarded as standard. The values given in parentheses are inch-pound units, which are provided for information only and are not considered standard.1.5 Precautions: 1.5.1 It is the responsibility of the user of this guide to follow any precautions within the equipment manufacturer’s recommendations, establish appropriate health and safety practices, and consider the safety and regulatory implications when explosives or any high-energy (mechanical or chemical) sources are used.1.5.2 If the method is applied at sites with hazardous materials, operations, or equipment, it is the responsibility of the user of this guide to establish appropriate safety and health practices and determine the applicability of any regulations prior to use.1.5.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 This guide is intended to encourage consistency and thoroughness in the reporting of geostatistical site investigations by describing the basic information required in a complete report.5.2 Referring to the table of contents suggested in Table 1, this guide may be used as a template by those preparing reports or as a checklist for review and auditing purposes by qualified nonparticipants in the study.1.1 This guide covers the contents required for a complete report of a geostatistical site investigation. A complete report is understood here to be one that contains all the information necessary to the understanding and evaluation of the geostatistical site investigation by other geostatisticians.1.2 This guide does not discuss the reporting of supplementary information that may assist evaluation of the report.1.3 While geostatistical methods are used in many fields, this guide is primarily intended for the reporting of environmental and geotechnical applications.1.4 The basic geostatistical methods referred to in this guide are fully described in texts by David (1),2 Journel and Huijbregts (2), Clark (3), and Isaaks and Srivastava (4). Olea (5) gives a thorough compilation of geostatistical terminology as well as (6) a practical description of the subject for engineers and earth scientists. Chiles (7) and Goovaerts (8) provide material on how to deal with spatial uncertainty and how to use geostatistics for the evaluation of natural resources.1.5 This guide does not discuss the reporting of multivariate, space-time, and other less-frequently used geostatistical methods; however this is not intended to reflect any judgment as to the validity of these methods.1.6 Geostatistics is but one approach that can be used to understand and describe site conditions. Investigations should incorporate whatever supplementary knowledge of the site that may be available from other sources. As with classical statistical approaches, geostatistics is not intended to establish cause-and-effect relationships.1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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This practice sets guidelines for the receiving, testing and reporting of result of the investigation of metal, ores and related materials that may constitute evidence that is or may become involved in litigation. It outlines procedures to be followed to document the nature and condition of the evidence, the planning and performance of the testing, and actions that involve altering the nature or condition of the evidence.1.1 This practice covers the procedures to be used for receiving, testing and reporting results of investigation of metals, ores, related materials or samples thereof that have been the subject of an incident that is or is reasonably expected to be the subject of litigation.1.2 This practice was developed particularly for cases involving civil litigation, however it can be applied to criminal cases where it does not conflict with applicable laws and regulations.

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4.1 This guide provides recommendations for recording walkway surface investigation, evaluation, and incident report data pertaining to slips, trips, stumbles, and falls. It is intended to aid individuals or entities in the development of their own special reporting system. It is recognized that a user may use this guide in its entirety or may extract only those segments providing the level of information recommended. Depending on the intended use, a report form may be designed to be used alone or as a supplement to or incorporated within another report form. This guide is not a final report form. It lists items that may be considered for inclusion into a questionnaire, document, or report.4.2 Potential users include persons interested in the prevention and investigation of slip, trip, stumble, and fall phenomena, such as insurance company loss control specialists, industrial and commercial safety professionals, plant and facilities management personnel, forensic engineers, and research personnel concerned with factor correlation, statistics acquisition, loss control, and cost control.4.3 This guide provides uniform language appropriate for creating a form for manually recording information regarding pedestrian walkway evaluations and slip, trip, and fall incidents.4.4 Recommendations for Reporting—Information specific to site location and case identification is given in 6.2; information specific to walkway evaluation is given in 6.3; information specific to slip, trip, and fall incidents is given in 6.4.1.1 This guide provides a listing of items that may be useful in recording and evaluating the conditions of a walkway surface, including ramps and stairs, that may involve a slip, stumble, or trip that may result in a fall.1.2 This guide provides a listing of data that may be useful in investigating, evaluating, and reporting a slip, stumble, trip, slip and fall, stumble and fall, or trip and fall incident.1.3 Nomenclature is provided to obtain uniform language for reports.1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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This guide covers the basic components for the development of a sexual assault investigation protocol, with specific attention to the examination of assault scenes, victims and suspects of sexual assault, the recovery of testimonial, physical, and behavioral evidence, and the preservation and custody of physical evidence. This guide also outlines procedures requiring the experience of experts in a diversity of fields. A multidisciplinary team approach to sexual assault investigation is necessary and is the current standard of care. This team should include members skilled in the following disciplines: law enforcement, criminalistics, victim advocacy, and clinical, forensic practice.1.1 This guide outlines the basic components for the development of a sexual violence investigation protocols, with specific attention to the examination of sexual violence scenes, victims and suspects of sexual violence, the recovery of testimonial, physical, and behavioral evidence, and the preservation and custody of physical evidence.1.2 This guide outlines protocols requiring the experience of experts in a diversity of fields. A multidisciplinary team approach to sexual violence investigation is necessary and is the current standard of care. This team should include members skilled in the following disciplines: law enforcement, criminalistics, victim advocacy, and clinical, forensic practice.1.3 This standard cannot replace knowledge, skills, or abilities acquired through education, training, and experience (see Practice E2917, Education and Training) and is to be used in conjunction with professional judgement by individuals with such discipline-specific knowledge, skills, and abilities.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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