1、Designation: D 7128 05Standard Guide forUsing the Seismic-Reflection Method for ShallowSubsurface Investigation1This standard is issued under the fixed designation D 7128; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 Purpose and Application:1.1.1 This guide summarizes the technique, equipment, fieldprocedures, data processing, and
3、interpretation methods for theassessment of shallow subsurface conditions using the seismic-reflection method.1.1.2 Seismic reflection measurements as described in thisguide are applicable in mapping shallow subsurface conditionsfor various uses including geologic (1), geotechnical, hydro-geologic (
4、2), and environmental (3).2The seismic-reflectionmethod is used to map, detect, and delineate geologic condi-tions including the bedrock surface, confining layers (aquita-rds), faults, lithologic stratigraphy, voids, water table, fracturesystems, and layer geometry (folds). The primary applicationof
5、 the seismic-reflection method is the mapping of lateralcontinuity of lithologic units and, in general, detection ofchange in acoustic properties in the subsurface.1.1.3 This guide will focus on the seismic-reflection methodas it is applied to the near surface. Near-surface seismicreflection applica
6、tions are based on the same principles asthose used for deeper seismic reflection surveying, but ac-cepted practices can differ in several respects. Near-surfaceseismic-reflection data are generally high-resolution (dominantfrequency above 80 Hz) and image depths from around6mtoas much as several hu
7、ndred meters. Investigations shallowerthan 6 m have occasionally been undertaken, but these shouldbe considered experimental.1.2 Limitations:1.2.1 This guide provides an overview of the shallowseismic-reflection method, but it does not address the details ofseismic theory, field procedures, data pro
8、cessing, or interpre-tation of the data. Numerous references are included for thatpurpose and are considered an essential part of this guide. It isrecommended that the user of the seismic-reflection method befamiliar with the relevant material in this guide, the referencescited in the text, and Guid
9、es D 420, D 653, D 2845, D 4428/D 4428M, Practice D 5088, Guides D 5608, D 5730, D 5753,D 6235, and D 6429.1.2.2 This guide is limited to two-dimensional (2-D) shal-low seismic-reflection measurements made on land. Theseismic-reflection method can be adapted for a wide variety ofspecial uses: on lan
10、d, within a borehole, on water, and in threedimensions (3-D). However, a discussion of these specializedadaptations of reflection measurements is not included in thisguide.1.2.3 This guide provides information to help understandthe concepts and application of the seismic-reflection methodto a wide r
11、ange of geotechnical, engineering, and groundwaterproblems.1.2.4 The approaches suggested in this guide for theseismic-reflection method are commonly used, widely ac-cepted, and proven; however, other approaches or modifica-tions to the seismic-reflection method that are technicallysound may be equa
12、lly suited.1.2.5 Technical limitations of the seismic-reflection methodare discussed in 5.4.1.2.6 This guide discusses both compressional (P) and shear(S) wave reflection methods. Where applicable, the distinctionsbetween the two methods will be pointed out in this guide.1.3 This guide offers an org
13、anized collection of informationor a series of options and does not recommend a specificcourse of action. This document cannot replace education orexperience and should be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in allcircumstances. This guide i
14、s not intended to represent orreplace the standard of care by which the adequacy of a givenprofessional service must be judged, nor should this documentbe applied without consideration for a projects many uniqueaspects. The word “Standard” in the title of this guide meansonly that the document has b
15、een approved through the ASTMconsensus process.1.4 The values stated in SI units are regarded as standard.The values given in parentheses are inch-pound units, whichare provided for information only and are not consideredstandard.1This guide is under the jurisdiction ofASTM Committee D18 on Soil and
16、 Rockand is the direct responsibility of Subcommittee D18.01 on Surface and SubsurfaceCharacterization.Current edition approved Jan. 1, 2005. Published February 2005.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.1Copyright ASTM International, 100 Bar
17、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.5 Precautions:1.5.1 It is the responsibility of the user of this guide tofollow any precautions within the equipment manufacturersrecommendations, establish appropriate health and safetypractices, and consider the safety
18、and regulatory implicationswhen explosives or any high-energy (mechanical or chemical)sources are used.1.5.2 If the method is applied at sites with hazardousmaterials, operations, or equipment, it is the responsibility ofthe user of this guide to establish appropriate safety and healthpractices and
19、determine the applicability of any regulationsprior to use.1.5.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-
20、bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 420 Guide to Site Characterization for Engineering, De-sign, and Construction PurposesD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2845 Test Method for Laboratory Determination of PulseVeloci
21、ties and Ultrasonic Elastic Constants of RockD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4428/D 4428M Test Method for Crosshole Seismic Test-ingD 5088 Practice for Decontamination of Fie
22、ld EquipmentUsed at Nonradioactive Waste SitesD 5608 Practice for Decontamination of Field EquipmentUsed at Low Level Radioactive Waste SitesD 5730 Guide to Site Characterization for EnvironmentalPurposes with Emphasis on Soil, Rock, the Vadose Zone,and Ground WaterD 5753 Guide for Planning and Cond
23、ucting Borehole Geo-physical LoggingD 5777 Guide for Using the Seismic Refraction Method forSubsurface InvestigationD 6235 Guide for Expedited Site Characterization of Haz-ardous Waste Contaminated SitesD 6429 Guide for Selecting Surface Geophysical MethodsD 6432 Guide for Using the Surface Ground P
24、enetratingRadar Method for Subsurface Investigation3. Terminology3.1 Definitions:3.1.1 For general terms, See Terminology D 653.Additionaltechnical terms used in this guide are defined in Refs (4) and(5).3.2 Definitions Specific to This Guide3.2.1 acoustic impedanceproduct of seismic compres-sional
25、wave velocity and density. Compressional wave velocityof a material is dictated by its bulk modulus, shear modulus,and density. Seismic impedance is the more general term forthe product of seismic velocity and density.3.2.2 automatic gain control (AGC)trace amplitude ad-justment that varies as a fun
26、ction of time and the amplitude ofadjacent data points. Amplitude adjustment changing the out-put amplitude so that at least one sample is at full scaledeflection within a selected moving window (moving in time).3.2.3 body wavesP- and S-waves that travel through thebody of a medium, as opposed to su
27、rface waves which travelalong the surface of a half-space.3.2.4 bulk modulus (elastic constant)the resistance of amaterial to change its volume in response to the hydrostaticload. Bulk modulus (K) is also known as the modulus ofcompression.3.2.5 check shot surveydirect measurement of traveltimebetwe
28、en the surface and a given depth. Usually sources on thesurface are recorded by a seismic receiver in a well todetermine the time-to-depth relationships at a specified loca-tion. Also referred to as downhole survey.3.2.6 coded sourcea seismic energy-producing devicethat delivers energy throughout a
29、given time in a predeterminedor predicted fashion.3.2.7 common mid-point (CMP) or common depth point(CDP) methoda recording-processing method in which eachsource is recorded at a number of geophone locations and eachgeophone location is used to record from a number of sourcelocations. After correcti
30、ons, these data traces are combined(stacked) to provide a common-midpoint section approximat-ing a coincident source and receiver at each location. Theobjective is to attenuate random effects and events whosedependence on offset is different from that of primary reflec-tions.3.2.8 compressional wave
31、 velocityalso known as P-wavevelocity. In seismic usage, velocity refers to the propagationrate of a seismic wave without implying any direction, that is,velocity is a property of the medium. Particle displacement ofa compressional wave is in the direction of propagation.3.2.9 dynamic rangethe ratio
32、 of the maximum reading tothe minimum reading which can be recorded by and read froman instrument without change of scale. It is also referred to asthe ability of a system to record very large and very smallamplitude signals and subsequently recover them. Integral tothe concept of dynamic range is t
33、he systems Analog to Digitalconverter (A/D). A systems A/D is rated according to thenumber of bits the analog signal is segmented into to form thedigital word. A/D converters in modern seismographs usuallyrange from 16 to 24 bits.3.2.10 fold (or redundancy)the multiplicity of common-midpoint data or
34、 the number of midpoints per bin. Where themidpoint is the same for 12 source/receiver pairs, the stack isreferred to as “12-fold” or 1200 percent.3.2.11 G-forcemeasure of acceleration relative to thegravitational force of the earth.3For referenced ASTM standards, visit the ASTM website, www.astm.or
35、g, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.D71280523.2.12 impedance contrastratio of the seismic impedanceacross a boundary. Seismic impedance of the lower layerdivided by
36、 the seismic impedance of the upper layer.Avalue of1 implies total transmittance. Values increase or decrease from1 as the contrast increases, that is, more energy reflection froma boundary. Values less than 1 are indicative of a negativereflectivity or reversed reflection wavelet polarity.3.2.13 no
37、rmal moveout (NMO)the difference inreflection-arrival time as a function of shot-to-geophone dis-tance because the geophone is not located at the source point.It is the additional traveltime required because of offset,assuming that the reflecting bed is not dipping and thatraypaths are straight line
38、s. This leads to a hyperbolic shape fora reflection.3.2.14 normal moveout velocity (stacking velocity)velocity to a given reflector calculated from normal-moveoutmeasurements, assuming a constant-velocity model. Becausethe raypath actually curves as the velocity changes, fitting ahyperbola assumes t
39、hat the actual velocity distribution isequivalent to a constant NMO velocity, but the NMO velocitychanges with the offset. However, the assumption often pro-vides an adequate solution for offsets less than the reflectordepth. Used to calculate NMO corrections to common-midpoint gathers prior to stac
40、king.3.2.15 Nyquist frequencyalso known as the aliasing orfolding frequency, is equal to half the sampling frequency orrate.Any frequency arriving at the recording instrument greaterthan the Nyquist will be aliased to a lower frequency andcannot be recovered.3.2.16 optimum windowrange of offsets bet
41、ween sourceand receiver that provide reflections with the best signal-to-noise ratio.3.2.17 Poissons ratiothe ratio of the transverse contrac-tion to the fractional longitudinal extension when a rod isstretched. If density is known, specifying Poissons ratio isequivalent to specifying the ratio of V
42、s/Vp, where Vsand VpareS- and P-wave velocities. Values ordinarily range from 0.5 (noshear strength, for example, fluid) to 0, but theoretically theyrange from 0.5 to 1.0; = =10.5(Vp/Vs)2/ 1(Vp/Vs)2.3.2.18 raypatha line everywhere perpendicular to wave-fronts (in isotropic media). A raypath is chara
43、cterized by itsdirection at the surface. While seismic energy does not travelonly along raypaths, raypaths constitute a useful method ofdetermining arrival time by ray tracing.3.2.19 reflectionthe energy or wave from a seismic sourcethat has been reflected (returned) from an acoustic-impedancecontra
44、st (reflector) or series of contrasts within the earth.3.2.20 reflectoran interface having a contrast in physicalproperties (elasticity and/or density) that reflects seismic en-ergy.3.2.21 roll-along switcha switch that connects differentgeophone groups to the recording instruments, used incommon-mi
45、dpoint recording.3.2.22 seismic impedanceproduct of seismic wave veloc-ity and density. Different from acoustic impedance as itincludes shear waves and surface waves where acoustic im-pedance, by strict definition, includes only compressionalwaves.3.2.23 seismic sensorreceivers designed to couple to
46、 theearth and record vibrations (for example, geophones, acceler-ometers, hydrophones).3.2.24 seismic sensor group (spread)multiple receiversconnected to a single recording channel, generally deployed inan array designed to enhance or attenuate specific energy.3.2.25 seismograma seismic record or se
47、ction.3.2.26 shear modulus (G) (elastic constant)the ratio ofshear stress to shear strain of a material as a result of loadingand is also known as the rigidity modulus, equivalent to thesecond Lam constant m mentioned in books on continuumtheory. For small deformations, Hookes law holds and strain i
48、sproportional to stress.3.2.27 shear wave velocity (S-wave velocity)speed ofenergy traveling with particle motion perpendicular to itsdirection of propagation (see Eq 2).3.2.28 shot gathera side-by-side display of seismic tracesthat have a common source location. Also referred to as “fieldfiles.”3.2
49、.29 source to seismic sensor offsetthe distance fromthe source-point to the seismic sensor or to the center of aseismic sensor (group) spread.3.2.30 takeouta connection point on a multiconductorcable where seismic sensors can be connected. Takeouts areusually physically polarized to reduce the likelihood of makingthe connection backwards.3.2.31 tap testgently touching a receiver while monitor-ing on real-time display, to qualitatively appraise sensorresponse.3.2.32 twist testlight rotational pressure applied to eachseismic sensor to ensure no
