ASTM D5777-00
(Guide)Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation
Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation
SCOPE
1.1 Purpose and Application -This guide summarizes the equipment, field procedures, and interpretation methods for the assessment of subsurface materials 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, mineral exploration, petroleum exploration, and archaeological investigations. The seismic refraction method can sometimes be used to map geologic conditions including depth to bedrock, or to water table, 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) can sometimes be made on the basis of seismic velocity and other geologic information.
1.2 Limitations:
1.2.1 This guide provides an overview of the seismic refraction method using compressional ( ) 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 within this guideline and the references provided.
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 wave measurements.
1.2.4 The approaches suggested in this guide for the seismic refraction method are most 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 5.4.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 5777 – 00
Standard Guide for
Using the Seismic Refraction Method for Subsurface
Investigation
This standard is issued under the fixed designation D 5777; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope guide is not intended to include this topic and focuses only on
P wave measurements.
1.1 Purpose and Application—This guide summarizes the
1.2.4 The approaches suggested in this guide for the seismic
equipment, field procedures, and interpretation methods for the
refraction method are commonly used, widely accepted, and
assessment of subsurface conditions using the seismic refrac-
proven; however, other approaches or modifications to the
tion method. Seismic refraction measurements as described in
seismic refraction method that are technically sound may be
this guide are applicable in mapping subsurface conditions for
substituted.
various uses including geologic, geotechnical, hydrologic,
1.2.5 Technical limitations and interferences of the seismic
environmental (1), mineral exploration, petroleum exploration,
refraction method are discussed in D 420, D 653, D 2845,
and archaeological investigations. The seismic refraction
D 4428, D 5088, D 5730, D 5753, D 6235, and D 6429.
method is used to map geologic conditions including depth to
1.3 Precautions:
bedrock, or to water table, stratigraphy, lithology, structure,
1.3.1 It is the responsibility of the user of this guide to
and fractures or all of these. The calculated seismic wave
follow any precautions within the equipment manufacturer’s
velocityisrelatedtomechanicalmaterialproperties.Therefore,
recommendations, establish appropriate health and safety prac-
characterization of the material (type of rock, degree of
tices, and consider the safety and regulatory implications when
weathering, and rippability) is made on the basis of seismic
explosives are used.
velocity and other geologic information.
1.3.2 If the method is applied at sites with hazardous
1.2 Limitations:
materials, operations, or equipment, it is the responsibility of
1.2.1 This guide provides an overview of the seismic
the user of this guide to establish appropriate safety and health
refraction method using compressional (P) waves. It does not
practices and determine the applicability of any regulations
address the details of the seismic refraction theory, field
prior to use.
procedures, or interpretation of the data. Numerous references
1.4 This standard does not purport to address all of the
are included for that purpose and are considered an essential
safety concerns, if any, associated with its use. It is the
part of this guide. It is recommended that the user of the
responsibility of the user of this standard to establish appro-
seismic refraction method be familiar with the relevant mate-
priate safety and health practices and determine the applica-
rial in this guide and the references cited in the text and with
bility of regulatory limitations prior to use.
appropriate ASTM standards cited in 2.1.
1.5 This guide offers an organized collection of information
1.2.2 This guide is limited to the commonly used approach
or a series of options and does not recommend a specific
to seismic refraction measurements made on land. The seismic
course of action. This document cannot replace education or
refraction method can be adapted for a number of special uses,
experienceandshouldbeusedinconjunctionwithprofessional
onland,withinaboreholeandonwater.However,adiscussion
judgment. Not all aspects of this guide may be applicable in all
of these other adaptations of seismic refraction measurements
circumstances. This guide is not intended to represent or
is not included in this guide.
replace the standard of care by which the adequacy of a given
1.2.3 There are certain cases in which shear waves need to
professional service must be judged, nor should this document
be measured to satisfy project requirements. The measurement
be applied without consideration of a project’s many unique
of seismic shear waves is a subset of seismic refraction. This
aspects. The word “Standard” in the title of this guide means
only that the document has been approved through the ASTM
This guide is under the jurisdiction of ASTM Committee D-18 on Soil and
consensus process.
Rock and is the direct responsibility of Subcommittee D18.01 on Surface and
Subsurface Characterization.
2. Referenced Documents
Current edition approved Feb. 10, 2000. Published May 2000. Originally
e1
2.1 ASTM Standards:
published as D 5777 – 95. Last previous edition D 5777 – 95 .
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5777–00
D 420 Guide to Site Characterization for Engineering, De- to characterize some of the properties of natural or man-made
sign and Construction Purposes man subsurface materials.
D 653 Terminology Relating to Soil, Rock, and Contained 4.2 Complementary Data—Geologic and water table data
Fluids obtained from borehole logs, geologic maps, data from out-
D 2845 Test Method for Laboratory Determination of Pulse crops or other complementary surface and borehole geophysi-
Velocities and Ultrasonic Elastic Constants of Rock cal methods may be necessary to properly interpret subsurface
D 4428/D 4428M TestMethodsforCrossholeSeismicTest- conditions from seismic refraction data.
ing
5. Significance and Use
D 5088 Practice for Decontamination of Field Equipment
Used at Nonradioactive Waste Sites
5.1 Concepts:
D 5608 Practice for Decontamination of Field Equipment
5.1.1 This guide summarizes the equipment, field proce-
Used at Low Level Radioactive Waste Sites
dures, and interpretation methods used for the determination of
D 5730 Guide to Site Characterization for Environmental
the depth, thickness and the seismic velocity of subsurface soil
Purposes with Emphasis on Soil, Rock, the Vadose Zone
and rock or engineered materials, using the seismic refraction
and Ground Water
method.
D 5753 Guide for Planning and Conducting Borehole Geo-
5.1.2 Measurement of subsurface conditions by the seismic
physical Logging
refraction method requires a seismic energy source, trigger
D 6235 Guide for Expedited Site Characterization of Va-
cable (or radio link), geophones, geophone cable, and a
dose Zone and Ground Water Contamination at Hazardous
seismograph (see Fig. 1).
Waste Contaminated Sites
5.1.3 The geophone(s) and the seismic source must be
D 6429 Guide for Selecting Surface Geophysical Methods
placed in firm contact with the soil or rock. The geophones are
usually located in a line, sometimes referred to as a geophone
3. Terminology
spread. The seismic source may be a sledge hammer, a
3.1 Definitions: mechanical device that strikes the ground, or some other type
of impulse source. Explosives are used for deeper refractors or
3.1.1 The majority of the technical terms used in this guide
are defined in Refs (2) and (3). Also see Terminology D 653. special conditions that require greater energy. Geophones
convert the ground vibrations into an electrical signal. This
4. Summary of Guide electrical signal is recorded and processed by the seismograph.
The travel time of the seismic wave (from the source to the
4.1 Summary of the Method—Measurements of the travel
geophone) is determined from the seismic wave form. Fig. 2
time of a compressional (P) wave from a seismic source to a
shows a seismograph record using a single geophone. Fig. 3
geophone(s) are made from the land surface and are used to
shows a seismograph record using twelve geophones.
interpret subsurface conditions and materials. This travel time,
5.1.4 Theseismicenergysourcegenerateselasticwavesthat
along with distance between the source and geophone(s), is
travel through the soil or rock from the source. When the
interpreted to yield the depth to refractors refractors (refracting
seismic wave reaches the interface between two materials of
layers).The calculated seismic velocities of the layers are used
different seismic velocities, the waves are refracted according
to Snell’s Law (4, 8). 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
Annual Book of ASTM Standards, Vol 04.08.
to the surface (Fig. 1). This interface is referred to as a
Annual Book of ASTM Standards, Vol 04.09.
The boldface numbers given in parentheses refer to a list of references at the
refractor.
end of the text.
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 (a = Critical Angle)
c
D5777–00
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.
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 to the refractor and the
seismic velocities of the materials through which the wave
passes.
5.1.10 Thedepthtoarefractoriscalculatedusingthesource
NOTE 1—Arrow marks arrival of first compressional wave.
togeophonegeometry(spacingandelevation),determiningthe
FIG. 2 A Typical Seismic Waveform from a Single Geophone
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 (6-8). 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 geom-
etry is known. These interpretation formulas are based on the
FIG. 3 Twelve-Channel Analog Seismograph Record Showing
Good First Breaks Produced by an Explosive Sound Source (9)
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 V is dependent upon the bulk
p
modulus, the shear modulus and the density in the following
manner (4):
V 5 @~K 1 4/3µ!/r# (1)
=
p
where:
V = compressional wave velocity,
p
K = bulk modulus,
µ = shear modulus, and
r = density.
5.1.7 The arrival of energy from the seismic source at each
geophone is recorded by the seismograph (Fig. 3). The travel
FIG. 4 (a) Seismic Raypaths and (b) Time-Distance Plot for a
time(thetimeittakesfortheseismic P-wavetotravelfromthe
Two-Layer Earth With Parallel Boundaries (9)
D5777–00
following assumptions: (1) the boundaries between layers are 5.1.13 The source of energy is usually located at or near
planes that are either horizontal or dipping at a constant angle, each end of the geophone spread; a refraction measurement is
(2) there is no land-surface relief, (3) each layer is homoge- made in each direction. These are referred to as forward and
neous and isotropic, (4) the seismic velocity of the layers reverse measurements, sometimes incorrectly called reciprocal
increases with depth, and (5) intermediate layers must be of measurements, from which separate time distance plots are
sufficient velocity contrast, thickness and lateral extent to be made. Fig. 6 shows the source and geophone layout and the
detected.Reference(9)providesanexcellentsummaryofthese resultingtimedistanceplotforadippingrefractor.Thevelocity
equations for two and three layer cases. The formulas for a obtained for the refractor from either of these two measure-
two-layered case (see Fig. 4) are given below. ments alone is the apparent velocity of the refractor. Both
5.1.10.1 Intercept-time formula: measurements are necessary to resolve the true seismic veloc-
ity and the dip of layers (9) unless other data are available that
t V V
i 2 1
z 5 (2)
indicateahorizontallayeredearth.Thesetwoapparentvelocity
2 2
~V ! 2 ~V !
=
2 1
measurements and the intercept time or crossover distance are
used to calculate the true velocity, depth and dip of the
where:
refractor. Note that only two depths of the planar refractor are
z = depth to refractor two,
obtainedusingthisapproach(seeFig.7).Depthtotherefractor
t = intercept time,
i
V = seismic velocity in layer two, and
is obtained under each geophone by using a more sophisticated
V = seismic velocity in layer one.
data collection and interpretation approach.
5.1.10.2 Crossover distance formula:
5.1.14 Most refraction surveys for geologic, engineering,
hydrologic and environmental applications are carried out to
x V 2 V
c 2 1
z 5 (3)
Œ
determine depths of refractors that are less than 100 m (about
2 V 1 V
2 1
300 ft). However, with sufficient energy, refraction measure-
where:
ments can be made to depths of 300 m (1000 ft) and more (6).
z, V and V are as defined above and x = crossover distance.
2 1 c
5.2 Parameter Measured and Representative Values:
5.1.11 Three to four layers are usually the most that can be
5.2.1 Theseismicrefractionmethodprovidesthevelocityof
resolved by seismic refraction measurements. Fig. 5 shows the
compressional P-waves in subsurface materials. Although the
sourceandgeophonelayoutandtheresultingtimedistanceplot
P-wave velocity is a good indicator of the type of soil or rock,
for an idealized three-layer case.
it is not a unique indicator. Table 1 shows that each type of
5.1.12 The refraction method is used to define the depth to
sediment or rock has a wide range of seismic velocities, and
or profile of the top of one or more refractors, or both, for
many of these ranges overlap. While the seismic refraction
example, depth to water table or bedrock.
technique measures the seismic velocity of seismic waves in
earthmaterials,itistheinterpreterwho,basedonknowledgeof
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 sedimenta
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