ASTM D5777-00(2011)e1
(Guide)Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation
Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation
SIGNIFICANCE AND USE
Concepts:
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.
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).
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.
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 (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 to the surface (Fig. 1). This interface is referred to as a refractor.
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).
The P-wave velocity Vp is dependent upon the bulk modulus, the sh...
SCOPE
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 to bedrock, or to 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 measuremen...
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D5777 − 00 (Reapproved 2011)
Standard Guide for
Using the Seismic Refraction Method for Subsurface
Investigation
This standard is issued under the fixed designation D5777; 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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Added a units statement as new 1.1.1 and revised Section 3 editorially in July 2011.
1. Scope 1.2.3 There are certain cases in which shear waves need to
be measured to satisfy project requirements. The measurement
1.1 Purpose and Application—This guide covers the
of seismic shear waves is a subset of seismic refraction. This
equipment, field procedures, and interpretation methods for the
guide is not intended to include this topic and focuses only on
assessment of subsurface conditions using the seismic refrac-
P wave measurements.
tion method. Seismic refraction measurements as described in
1.2.4 Theapproachessuggestedinthisguidefortheseismic
this guide are applicable in mapping subsurface conditions for
refraction method are commonly used, widely accepted, and
various uses including geologic, geotechnical, hydrologic,
proven; however, other approaches or modifications to the
environmental (1), mineral exploration, petroleum exploration,
seismic refraction method that are technically sound may be
and archaeological investigations. The seismic refraction
substituted.
method is used to map geologic conditions including depth to
bedrock, or to water table, stratigraphy, lithology, structure,
1.2.5 Technical limitations and interferences of the seismic
and fractures or all of these. The calculated seismic wave
refraction method are discussed in D420, D653, D2845,
velocityisrelatedtomechanicalmaterialproperties.Therefore,
D4428/D4428M, D5088, D5730, D5753, D6235, and D6429.
characterization of the material (type of rock, degree of
1.3 Precautions:
weathering, and rippability) is made on the basis of seismic
1.3.1 It is the responsibility of the user of this guide to
velocity and other geologic information.
follow any precautions within the equipment manufacturer’s
1.1.1 The geotechnical industry uses English or SI units.
recommendations, establish appropriate health and safety
1.2 Limitations:
practices, and consider the safety and regulatory implications
1.2.1 This guide provides an overview of the seismic
when explosives are used.
refraction method using compressional (P) waves. It does not
1.3.2 If the method is applied at sites with hazardous
address the details of the seismic refraction theory, field
materials, operations, or equipment, it is the responsibility of
procedures, or interpretation of the data. Numerous references
the user of this guide to establish appropriate safety and health
are included for that purpose and are considered an essential
practices and determine the applicability of any regulations
part of this guide. It is recommended that the user of the
prior to use.
seismic refraction method be familiar with the relevant mate-
rial in this guide and the references cited in the text and with 1.4 This standard does not purport to address all of the
appropriate ASTM standards cited in 2.1.
safety concerns, if any, associated with its use. It is the
1.2.2 This guide is limited to the commonly used approach responsibility of the user of this standard to establish appro-
to seismic refraction measurements made on land. The seismic priate safety and health practices and determine the applica-
refraction method can be adapted for a number of special uses, bility of regulatory limitations prior to use.
onland,withinaboreholeandonwater.However,adiscussion
1.5 This guide offers an organized collection of information
of these other adaptations of seismic refraction measurements
or a series of options and does not recommend a specific
is not included in this guide.
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 repre-
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock
and is the direct responsibility of Subcommittee D18.01 on Surface and Subsurface
sent or replace the standard of care by which the adequacy of
Characterization.
a given professional service must be judged, nor should this
Current edition approved July 1, 2011. Published September 2011. Originally
document be applied without consideration of a project’s many
approved in 1995. Last previous edition approved in 2006 as D5777 – 00 (2006).
DOI: 10.1520/D5777-00R11E01. unique aspects. The word “Standard” in the title of this guide
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D5777 − 00 (2011)
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 (α = Critical Angle)
c
means only that the document has been approved through the 3.2.1 The majority of the technical terms used in this guide
ASTM consensus process. are defined in Refs (2) and (3).
4. Summary of Guide
2. Referenced Documents
4.1 Summary of the Method—Measurements of the travel
2.1 ASTM Standards:
time of a compressional (P) wave from a seismic source to a
D420 Guide to Site Characterization for Engineering Design
geophone(s) are made from the land surface and are used to
and Construction Purposes (Withdrawn 2011)
interpret subsurface conditions and materials. This travel time,
D653 Terminology Relating to Soil, Rock, and Contained
along with distance between the source and geophone(s), is
Fluids
interpreted to yield the depth to refractors refractors (refracting
D2845 Test Method for Laboratory Determination of Pulse
layers).The calculated seismic velocities of the layers are used
Velocities and Ultrasonic Elastic Constants of Rock
to characterize some of the properties of natural or man-made
D4428/D4428M Test Methods for Crosshole Seismic Test-
man subsurface materials.
ing
D5088 Practice for Decontamination of Field Equipment
4.2 Complementary Data—Geologic and water table data
Used at Waste Sites
obtained from borehole logs, geologic maps, data from out-
D5608 Practices for Decontamination of Field Equipment
crops or other complementary surface and borehole geophysi-
Used at Low Level Radioactive Waste Sites
cal methods may be necessary to properly interpret subsurface
D5730 Guide for Site Characterization for Environmental
conditions from seismic refraction data.
Purposes With Emphasis on Soil, Rock, the Vadose Zone
5. Significance and Use
and Groundwater (Withdrawn 2013)
D5753 Guide for Planning and Conducting Borehole Geo-
5.1 Concepts:
physical Logging
5.1.1 This guide summarizes the equipment, field
D6235 Practice for Expedited Site Characterization of Va-
procedures, and interpretation methods used for the determi-
dose Zone and Groundwater Contamination at Hazardous
nation of the depth, thickness and the seismic velocity of
Waste Contaminated Sites
subsurface soil and rock or engineered materials, using the
D6429 Guide for Selecting Surface Geophysical Methods
seismic refraction method.
5.1.2 Measurement of subsurface conditions by the seismic
3. Terminology
refraction method requires a seismic energy source, trigger
cable (or radio link), geophones, geophone cable, and a
3.1 Definitions:
seismograph (see Fig. 1).
3.1.1 Definitions shall be in accordance with the terms and
5.1.3 The geophone(s) and the seismic source must be
symbols given in Terminology D653.
placed in firm contact with the soil or rock. The geophones are
3.2 Definitions of Terms Specific to This Standard:
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
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
of impulse source. Explosives are used for deeper refractors or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 4
The last approved version of this historical standard is referenced on The boldface numbers given in parentheses refer to a list of references at the
www.astm.org. end of the text.
´1
D5777 − 00 (2011)
NOTE 1—Arrow marks arrival of first compressional wave.
FIG. 2 A Typical Seismic Waveform from a Single Geophone
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
FIG. 3 Twelve-Channel Analog Seismograph Record Showing
geophone) is determined from the seismic wave form. Fig. 2
Good First Breaks Produced by an Explosive Sound Source (4)
shows a seismograph record using a single geophone. Fig. 3
shows a seismograph record using twelve geophones.
5.1.9 The travel time of the seismic wave between the
5.1.4 Theseismicenergysourcegenerateselasticwavesthat
seismic energy source and a geophone(s) is a function of the
travel through the soil or rock from the source. When the
distance between them, the depth to the refractor and the
seismic wave reaches the interface between two materials of
seismic velocities of the materials through which the wave
different seismic velocities, the waves are refracted according
passes.
to Snell’s Law (5, 6). When the angle of incidence equals the
5.1.10 Thedepthtoarefractoriscalculatedusingthesource
critical angle at the interface, the refracted wave moves along
togeophonegeometry(spacingandelevation),determiningthe
the interface between two materials, transmitting energy back
apparent seismic velocities (which are the reciprocals of the
to the surface (Fig. 1). This interface is referred to as a
slopes of the plotted lines in the time distance plot), and the
refractor.
intercept time or crossover distances on the time distance plot
5.1.5 A number of elastic waves are produced by a seismic
(see Fig. 4). Intercept time and crossover distance-depth
energy source. Because the compressional P -wave has the
formulas have been derived in the literature (7-6). These
highest seismic velocity, it is the first wave to arrive at each
derivations are straightforward inasmuch as the travel time of
geophone (see Fig. 2 and Fig. 3).
5.1.6 The P-wave velocity V is dependent upon the bulk the seismic wave is measured, the velocity in each layer is
p
calculated from the time-distance plot, and the raypath geom-
modulus, the shear modulus and the density in the following
manner (5): etry is known. These interpretation formulas are based on the
following assumptions: (1) the boundaries between layers are
V 5 =@~K14/3µ!/ρ# (1)
p
planes that are either horizontal or dipping at a constant angle,
( 2) there is no land-surface relief, (3) each layer is homoge-
where:
neous and isotropic, (4) the seismic velocity of the layers
V = compressional wave velocity,
p
increases with depth, and (5) intermediate layers must be of
K = bulk modulus,
sufficient velocity contrast, thickness and lateral extent to be
µ = shear modulus, and
detected.Reference (4)providesanexcellentsummaryofthese
ρ = density.
equations for two and three layer cases. The formulas for a
5.1.7 The arrival of energy from the seismic source at each
two-layered case (see Fig. 4) are given below.
geophone is recorded by the seismograph (Fig. 3). The travel
5.1.10.1 Intercept-time formula:
time(thetimeittakesfortheseismic P-wavetotravelfromthe
t V V
seismic energy source to the geophone(s)) is determined from i 2 1
z 5 (2)
2 2 2
each waveform. The unit of time is usually milliseconds (1 ms
= V 2 V
~ ! ~ !
2 1
= 0.001 s).
where:
5.1.8 The travel times are plotted against the distance
z = depth to refractor two,
between the source and the geophone to make a time distance
t = intercept time,
i
plot. Fig. 4 shows the source and geophone layout and the
V = seismic velocity in layer two, and
resulting idealized time distance plot for a horizontal two-
V = seismic velocity in layer one.
layered earth.
´1
D5777 − 00 (2011)
FIG. 5 (a) Seismic Raypaths and (b) Time-Distance Plot for a
Three-Layer Model With Parallel Boundaries (4)
FIG. 4 (a) Seismic Raypaths and (b) Time-Distance Plot for a
Two-Layer Earth With Parallel Boundaries (4)
5.1.10.2 Crossover distance formula:
x V 2 V
c 2 1
z 5 Π(3)
2 V 1V
2 1
where:
z, V and V are as defined above and x = crossover distance.
2 1 c
5.1.11 Three to four layers are usually the most that can be
resolved by seismic refraction measurements. Fig. 5 shows the
sourceandgeophonelayoutandtheresultingtimedistanceplot
for an idealized three-layer case.
5.1.12 The refraction method is used to define the depth to
or profile of the top of one or more refractors, or both, for
FIG. 6 (a) Seismic Raypaths and (b) Time-Distance Plot for a
example, depth to water table or bedrock.
Two-Layer Model With A Dipping Boundary (4)
5.1.13 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 and the intercept time or crossover distance are
measurements, from which separate time distance plots are used to calculate the true velocity, depth and dip of the
made. Fig. 6 shows the source and geophone layout and the refractor. Note that only two depths of the planar refractor are
resultingtimedistanceplotforadippingrefractor.Thevelocity obtainedusingthisapproach(seeFig.7).Depthtotherefractor
obtained for the refractor from either of these two measure- is obtained under each geophone by using a more sophisticated
ments alone is the apparent velocity of the refractor. Both data collection and interpretation approach.
measurements are necessary to resolve the true seismic veloc- 5.1.14 Most refraction surveys for geologic, engineering,
ity and the dip of layers (4) unless other data are available that hydrologic and environmental applications are carried out to
indicateahorizontallayeredearth.Thesetwoapparentvelocity determine depths of refractors that are less than 100 m (about
´1
D5777 − 00 (2011)
TABLE 1 Range of Velocities For Compressional Wave
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.