2013

RAGHU VANSH BHUSHAN SINGH

Ridings Consulting Engineers (I) Pvt Ltd

4/10/2013

Geo-technical Engineering- Seismic

Purpose and Application

This guide summarizes 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, 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.

Overview of Seismic wave

Seismic waves are waves of energy that travel through the Earth's layers, and are a result of

an earthquake, explosion, or a volcano that imparts low-frequency acoustic energy. Many other

natural and anthropogenic sources create low amplitude waves commonly referred to as ambient

vibrations. Seismic waves are studied by geophysicists called seismologists. Seismic wave fields

are recorded by a seismometer, hydrophone (in water), or accelerometer.

The propagation velocity of the waves depends on density and elasticity of the medium. Velocity

tends to increase with depth, and ranges from approximately 2 to 8 km/s in the Earth's crust up to

13 km/s in the deep mantle.

Types of seismic waves

There are many types of seismic waves,

1. Body wave,

2. Surface waves

1. Body waves

Body waves travel through the interior of the Earth. They create raypaths refracted by the

varying density and modulus (stiffness) of the Earth's interior. The density and modulus, in turn,

vary according to temperature, composition, and phase. This effect is similar to

the refraction of light waves. These are two types-

A. Primary wave or P-wave

B. Secondary wave or S-wave

A. Primary waves

Primary waves (P-waves) are compressional waves that are longitudinal in nature. P waves are

pressure waves that travel faster than other waves through the earth to arrive at seismograph

stations first hence the name "Primary". These waves can travel through any type of material,

including fluids, and can travel at nearly twice the speed of S waves. In air, they take the form of

sound waves; hence they travel at the speed of sound. Typical speeds are 330 m/s in air,

1450 m/s in water and about 5000 m/s in granite. Primary waves also travel about 1 to 5 miles

per second (1.6 to 8 kps), depending on the material they're moving through.

The velocity of P-waves in a homogeneous isotropic medium is given by

where K is the bulk modulus (the modulus of incompressibility), is the shear

modulus (modulus of rigidity, sometimes denoted as Gand also called the second Lamé

parameter), is the density of the material through which the wave propagates, and is the

first Lamé parameter.

B. Secondary waves

Secondary waves (S-waves) are shear waves that are transverse in nature. These waves arrive at

seismograph stations after the faster moving P waves during an earthquake and displace the

ground perpendicular to the direction of propagation. Depending on the propagational direction,

the wave can take on different surface characteristics; for example, in the case of horizontally

polarized S waves, the ground moves alternately to one side and then the other. S waves can

travel only through solids, as fluids (liquids and gases) do not support shear stresses. S waves are

slower than P waves, and speeds are typically around 60% of that of P waves in any given

material.

The velocity of S-waves in a homogeneous isotropic medium is given by

Vs = ( / )1/2

2. Surface waves

Surface waves (L-waves) are analogous to water waves and travel along the Earth's surface.

They travel slower than body waves. Because of their low frequency, long duration, and large

amplitude, they can be the most destructive type of seismic wave. They are called surface waves

because they diminish as they get further from the surface. These are of two types-

A. Rayleigh waves

B. Love waves

Rayleigh waves

Rayleigh waves, also called ground roll, are surface waves that travel as ripples with motions

that are similar to those of waves on the surface of water (note, however, that the associated

particle motion at shallow depths is retrograde, and that the restoring force in Rayleigh and in

other seismic waves is elastic, not gravitational as for water waves). The existence of these

waves was predicted by John William Strutt, Lord Rayleigh, in 1885. They are slower than body

waves, roughly 90% of the velocity of S waves for typical homogeneous elastic media.

Love waves

Love waves are horizontally polarized shear waves (SH waves), existing only in the presence of

a semi-infinite medium overlain by an upper layer of finite thickness.[1]

They are named

after A.E.H. Love, a British mathematician who created a mathematical model of the waves in

1911. They usually travel slightly faster than Rayleigh waves, about 90% of the S wave velocity,

and have the largest amplitude.

Seismic wave traveltime from an earthquake data

Near Surface Seismic Refraction Survey Methods (P wave):

The seismic refraction method

•First major geophysical method applied to subsurface investigation of relatively deep oil-

bearing geologic structures

•No longer the primary method in oil exploration, but has found use for near-surface, high-

resolution subsurface investigation

•Common applications for civil engineering and environmental studies include depth-to-bedrock

and groundwater investigations; also used for shallow fault and stratigraphic studies

•Main objective is to measure the time of the “first break”, that is, the time when a given

geophone first moves in response to a seismic energy source. Simply stated, since time and

relative distances of sources and geophones are known, the velocity of the subsurface can be

calculated.

Typical equipment

•Seismograph

–12 to 24 channels

•Sensors and spread cable

–8, 10, or 14 Hz vertical geophones

–2 to 5-m (5 to 20-ft) spread cable takeout interval

•Source

–10 to 20-pound sledgehammer with hammer switch, trigger cable, and striker plate

Seismographs

Laptop controller for ES-3000 or GeodeGeode. Geometrics

StrataVisor NZ

(PC built-in) Geometrics

SmartSeis ST

(PC built-in)

RAS-24 Exploration Seismograph, Seistronix

RAS-24 basic system

RAS-24 24 channel system

Telemetric seismic station SGD-TEL, a Zond Product

APPLICATIONS of Seismograph:

Oil & gas exploration

Mineral exploration

Geotechnical surveys

Engineering geology

Groundwater surveys

VSP and tomography

Depth-to-rock

Fault location

Site remediation

Surface wave analysis

Rippability surveys

Teaching and research

1. Survey of weathered layer (Low velocity layer):

(On basis of Experience of previous companies C.A.T. Geo-data GmbH. Vienna. And Shiv-Vani Oil &

Gas Exploration Services Ltd. India)

Survey geometry –sensors

•Geophones are distributed in a line, signals are transmitted to the seismograph by a spread

cable.

•The total offset should be 3 to 5 times the depth of interest. However, this should be balanced

against the number of channels available and the required horizontal resolution. If too few

channels are used to span a large total offset, the horizontal resolution will suffer.

Survey geometry –coordinates

•At a minimum, relative x, y spacing is required

–Easiest to save to the file header at time of acquisition, but can also be assigned in data analysis

software

–Set y equal to zero, and vary x values only (or vice versa)

–Some deviation from a line can be tolerated, minimize deviation to 5% or less of the line length

•If there is any vertical relief on the line, the elevations should be surveyed

–Elevations only need be relative, unless referenced elevations are desired

–Z values are not saved in file header, but are easily input into data analysis software

Typical recording parameters

•Sample interval: 0.125 to 0.25 ms (over-sampling is fine)

•Record length: 0.25 to 0.5 s (should be long enough to capture distant arrivals)

•Stacking: as needed to increase signal to noise ratio, 5 to 10 times

•Delay: -10 ms allows the first break on the near geophones to be more easily viewed

•Acquisition filters: acquisition filters are NOT recommended because effect is irreversible;

should be carefully applied to filter signal you are certain you will never want such as 60 Hz

power line noise

•Preamp gains: highest setting

•Display gains: fixed gain (same gain over time for a given trace, but variable from trace to trace;

traces far from the source will need a higher gain setting than those that are near)

Seismogram using Ras-24

Analysis of the first and second end shots

•Analyze waveform file of the first end shot

–What is the data quality? There is little pre-first break noise, the first breaks are obvious.

Quality is excellent.

– How many refractions are there? One break in slope indicates one refraction (two-layers).

–What is the crossover distance*? Break in slope is 5 traces in. Five multiplied by a geophone

interval of 2m equals 10m

Picking first breaks

•Set the display gains so the first breaks are clearly visible

–Ground roll has relatively large amplitude and can be misidentified as the first arrival if the

display gains are not high enough

–Use display clipping so the traces do not overlap when the gain is set very high

Data Table

Station

No.

Station

Int(m)

Station

Distance(m)

First Break

Forward(msec)

First Break

Reverse(msec)

1 2 2 2 90

2 2 4 9 89

3 3 7 16 88

4 3 10 23 87

5 4 14 30 86

6 4 18 34 83

7 4 22 38 80

8 5 27 42 77

9 5 32 46 74

10 7 39 50 70

11 7 46 54 66

12 9 55 58 62

13 9 64 62 58

14 7 71 66 54

15 7 78 70 50

16 5 83 74 46

17 5 88 77 42

18 4 92 80 38

19 4 96 83 34

20 4 100 86 30

21 3 103 87 23

22 3 106 88 16

23 2 108 89 9

24 2 110 90 2

Xc

Velocity Analysis

Formula Used:

V1 = Δx(m)/Δt(ms)

Where V1 = the velocity of sound in layer I

Δx = change in distance (m)

Δt = change in time (ms)

The depth to the second layer or

d= (Xc)/2*[(V2-V1)/(V2+V1)]1/2

Where Xc = crossover distance

V1 = velocity of sound in layer one

V2 = velocity of sound in layer two

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70 80 90 100 110

Trav

el T

ime

(m

s)

Distance (m)

Forward(msec)

Reverse(msec)

Table 1 Result of the Survey

Location V1 (ms) V2 (ms) Depth (m)

1 400 800 7.47

Table 2: Established standard P – wave Velocities

Rock Type

Standard P-Wave Velocity (ms)

Granite 5520 – 56040

Sandstone 1400 – 4300

Limestone 1700 – 4200

Clay 1100 – 4200

Loose sand 1800

Coarse sand (wet) 1150 – 1670

Sand with gravel (wet) 690 – 1150

Sand with gravel (dry) 490 – 690

Sandy clay 360 – 430

2. Up-Hole Survey (P Wave):

Drilling for Up-Hole Survey:

Blaster Recording unit RAS-24

X Geophone

Drilled Hole

vt

Ɵ

Point of detonation S2 ‘d’

Point of detonation S1

Data acquisition and methodology

(On basis of Experience of previous companies C.A.T. Geo-data GmbH. Vienna. And Shiv-Vani Oil &

Gas Exploration Services Ltd. India)

In the up-hole survey, a deep hole is drilled at the intersection of source and receiver line in a

seismic refraction data acquisition project. In this procedure, dynamite charges are laid

successively in the hole at intervals starting from the deepest depth level of interest, each charge

having a detonator lid extending to the surface with the depth written on it. The hole is tamped

after each shot is laid to prevent loss of energy up the hole when a shot is taken. Therefore, a

number of geophones are laid on the surface at respective intervals from the hole. At the end of

the shooting, a single geophone jug is planted near the surface very close to the hole and a shot

taken with a detonator cap planted near the surface in the hole. The idea is to obtain an up-hole

pre-trigger time, which is the time that would elapse between the initiation of a shot and its

reception by a geophone. Figure is a sketch of the field arrangement for the data acquisition.

Data processing

After a shot is taken, a plot of arrival times versus geophone offset is made on a monitor record

and this constitutes the data set (Table). In processing of the data, first-break arrival times are

picked for various shots. First-break time is the first pick-up time recognized for any trace, and is

the parameter of interest in the interpretation of up-hole survey data. The up-hole survey data are

normalized by subtracting the pre-trigger time from the first-break time. By this, it is assumed

that the pick-up time of a shot by each geophone is the same; therefore, differences are due to

time delays introduced into the data by the weathering layer. Near to surface depth models are

computed from picked first to break time; and to achieve this, a plot of the corrected time is

made against each channel for every shot in the up-hole survey method. From this, it is seen that

the depth of the weathering layer computation is based on the zero to offset time which is

obtained by extrapolating the refraction curve to the time axis.

Data interpretation

Normally in the interpretation of the up-hole survey data, computation of the weathering depth is

a function of the plot in question. If the plot is such that the up-hole time is less than the intercept

time (Figure); it implies that the shot is in the weathering layer and Equation may be sufficient in

determining the weathering thickness. When the intercept time is less than the up-hole time, the

curve is no longer that of refraction but reflection, and the inverse slope gives the velocity in the

consolidated layer. The implication here is that the shot is at the base of the weathering layer or

within the consolidated layer. Here, the ray’s path crosses the weathering layer only once and the

weathering depth can be computed from Equation. However, at some shot depths the up-hole and

intercept times would be approximate. This immediately gives the clue to the depth of the

weathering layer because the shot depth at this instant is close the base of the weathering.

COSƟ=d/vt

COSƟ= d/(d2 +X

2)1/2

ie v= t/(d2 +X

2)1/2

Where

X= Geophone distance from hole

d= depth of detonation

v= velocity of medium

t= travel time of energy

Picking first breaks

•Set the display gains so the first breaks are clearly visible

–Ground roll has relatively large amplitude and can be misidentified as the first arrival if the

display gains are not high enough

–Use display clipping so the traces do not overlap when the gain is set very high

Table - break listing for up-hole data.

Result of the Survey

Location V1 (ms) V2 (ms) Depth (m)

1 450 1800 14.0

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

Trav

el T

ime

(m

s)

Depth (m)

Depth

of Charge Travel time

10 10.9

15 13.4

20 18.9

25 19.4

30 21

35 22

40 22.5

45 23

50 23.5

55 24

60 24.5

65 25

Established standard P – wave Velocities

Rock Type

Standard P-Wave Velocity (ms)

Granite 5520 – 56040

Sandstone 1400 – 4300

Limestone 1700 – 4200

Clay 1100 – 4200

Loose sand 1800

Coarse sand (wet) 1150 – 1670

Sand with gravel (wet) 690 – 1150

Sand with gravel (dry) 490 – 690

Sandy clay 360 – 430

3. Cross-hole survey(P wave and S wave):

(Field procedure is almost same as Up-hole survey)

Objectives of the study

The main objectives for this study are to:

• Determine the dynamic soil properties as a function of depth.

• Define the advantages and disadvantages of each method in relation to local site characteristics.

• Correlate and Compare the result between the different methods in order to validate the

modeling results.

• Propose predictive equation models for the assessment of Vs based on the geophysical methods

and geotechnical parameters.

The mechanical properties associated with dynamic loading are:

1.) Shear wave velocity (Vs).

2.) Shear modulus (G).

3.) Young's modulus (E).

4.) Poisson’s ratio (ʋ).

Dynamic soil properties are calculated from corresponding compression (Vp) and shear wave

(Vs) velocities and in-situ bulk densities (ρ) using standard equations based on elastic theory.

Elastic Moduli Parameters:

Shear Modulus (G):G= ρVs2

Young Modulus (E):E=2G(1+ ʋ)

Bulk Modulus (K):K=(1/3)*[E/(1-2ʋ)]

Poisson’s ratio (ʋ):ʋ=0.5[(Vp / Vs)

2-2]/ [(Vp

/ Vs)

2-1]

Requirements:

•At least two cased hole.

•Borehole Source (P&S) waves.

•One or two clamping tri axial geophones.

•Seismograph

Measurements:

•Compressional-wave velocity.

•Shear-wave velocity

•Bulk density (This parameter is provided by Geo-technical Laboratory after providing them soil

samples of various depths from bore hole)

1. Brief Theory

1.1 These test methods are limited to the determination of horizontally traveling compression (P)

i.e. (Vp) and shear (S) i.e.(Vs) seismic waves at test sites consisting primarily of soil materials

(as opposed to rock). A preferred test method intended for use on critical projects where the

highest quality data must be obtained is included. Also included is an optional method intended

for use on projects which do not require measurements of a high degree of precision.

1.2 Various applications of the data will be addressed and acceptable interpretation procedures

and equipment, such as seismic sources, receivers, and recording systems will be discussed.

Other items addressed include borehole spacing, drilling, casing, grouting, deviation surveys, and

actual test conduct. Data reduction and interpretation is limited to the identification of various

seismic wave types, apparent velocity relation to true velocity, example computations, effective

borehole spacing, and use of Snell’s law of refraction, assumptions, and computer programs.

1.3 It is important to note that more than one acceptable device can be used to generate a high-

quality P wave or S wave, or both. Further, several types of commercially available receivers and

recording systems can also be used to conduct an acceptable crosshole survey. Consequently,

these test methods primarily concern the actual test procedure, data interpretation, and

specifications for equipment which will yield uniform test results.

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.

2. Significance and Use

2.1 The seismic crosshole method provides a designer with information pertinent to the seismic

wave velocities of the materials .2 This data may be used as input into static/dynamic analyses,

as a means for computing shear modulus, Young’s modulus, and Poisson’s ratio, or simply for

the determination of anomalies that might exist between boreholes.

2.2 Fundamental assumptions inherent in the test methods are as follows:

2.2.1 Horizontal layering is assumed.

2.2.2 Snell’s laws of refraction will apply. If Snell’s laws of refraction are not applied, velocities

obtained will be unreliable.

3. Apparatus

3.1 The basic data acquisition system consists of the following:

3.1.1 Energy Sources—these energy sources are chosen according to the needs of the survey, the

primary consideration being whether P-wave or S-wave velocities are to be determined. The

source should be rich in the type of energy required, that is, to produce good P-wave data, the

energy source must transmit adequate energy to the medium in compression or volume change.

Impulsive sources, such as explosives, hammers, or air guns, are all acceptable P-wave

generators. To produce an identifiable S wave, the source should transmit energy to the ground

primarily by directionalized distortion. For good S waves, energy sources must be repeatable

and, although not mandatory, reversible. The S-wave source must be capable of producing an S-

wave train with amplitude at least twice that of the P-wave train.

3.1.2 Receivers—the receivers intended for use in the crosshole test shall be transducers having

appropriate frequency and sensitivity characteristics to determine the seismic wave train arrival.

Typical examples include geophones and accelerometers. The frequency response of the

transducer must not vary more than 5 % over a range of frequencies from 1 to 2 times the

predominant frequency of the site-specific S-wave train. Each receiving unit will consist of at

least three transducers combined orthogonally to form a triaxial array, that is, one vertical and

two horizontal transducers mounted at right angles, one to the other. In this triaxis arrangement,

only the vertical component will be acceptable for S-wave arrival determinations. In cases where

P-wave arrivals are not desired, a uniaxial vertical transducer may be used. P-wave arrivals will

be determined using the horizontal transducer oriented most nearly radially to the source. The

transducer(s) shall be housed in a single container (cylindrical shape preferred) not exceeding

450 mm [18 in.] in length. Provision must be made for the container to be held in firm contact

with the sidewall of the borehole. Examples of acceptable methods include: air bladder, wedge,

stiff spring, or mechanical expander.

3.1.3 Recording System— the system shall consist of separate amplifiers, one for each transducer

being recorded, having identical phase characteristics and adjustable gain control. Only digital

signal filtering will be acceptable. Analog filtering, active or passive, will not be acceptable

because of inherent phase delays. The receiver signals shall be displayed in a manner such that

precision timing of the P and S-wave arrival referenced to the instant of seismic source activation

can be determined within 0.1 ms when materials other than rock are being tested. Timing

accuracy shall be demonstrated both immediately prior to and immediately after the conduct of

the crosshole test. Demonstrate accuracy by inducing and recording on the receiver channels an

oscillating signal of 1000 Hz derived from a quartz-controlled oscillator, or, a certified

laboratory calibration obtained within the time frame recommended by the instrument

manufacturer. Further, the timing signal shall be recorded at every sweep rate or recorder speed,

or both, used during conduct of the crosshole test. As an optional method, the true zero time shall

be determined by (1) a simultaneous display of the triggering mechanism along with at least one

receiver, or (2) a laboratory calibration (accurate to 0.1 ms) of the triggering mechanism which

will determine the lapsed time between the trigger closure and development of that voltage

required to initiate the sweep on an oscilloscope or seismograph. Permanent records of the

seismic events shall be made by either scope-mounted camera or oscillograph.

4. Procedure

4.1 Borehole Preparation:

4.1.1 Preferred—the preferred method for preparing a borehole set for crosshole testing

incorporates three boreholes in line, spaced 3.0 m [10 ft] apart, center-to-center on the ground

surface, as illustrated in Fig. 3. If, however, it is known that S wave velocities will exceed 450

m/s [1500 ft/s], such as is often encountered in alluvial materials, borehole spacing may be

extended to 4.5 m [15 ft].

4.1.1.1 Drill the boreholes, with minimum sidewall disturbance, to a diameter not exceeding 165

mm [6.5 in.]. After the drilling is completed, case the boring with either 75 or 100 mm [3 or 4

in.] inside diameter PVC pipe or aluminum casing. Before inserting the casing, close the bottom

of the pipe with a cap which has a one way ball-check valve capable of accommodating 38 mm

[11⁄2 in.] outside diameter grout pipe.

Center the casing with spacers and insert it into the bottom of the borehole. Grout the casing in

place by (1) inserting a 38mm [11⁄2 in.] PVC pipe through the center of the casing, contacting

the one-way valve fixed to the end cap by a small diameter grout tube inserted to the bottom of

the borehole between the casing and the borehole sidewall. Another acceptable method would be

to fill the borehole with grout which would be displaced by end-capped fluid-filled casing. The

grout mixture should be formulated to approximate closely the density of the surrounding in situ

material after solidification. That portion of the boring that penetrates rock should be grouted

with a conventional portland cement which will harden to a density of about 2.20 Mg/m3 [140

lb/ft3]. That portion of the boring in contact with soils, sands, or gravels should be grouted with a

mixture simulating the average density of the medium (about 1.80 to 1.90 Mg/m 3 [110 to 120

lb/ft3]) by premixing 450 g [1 lb] of bentonite and 450 g [1 lb] of portland cement to 2.80 kg

[6.25 lb] of water. Anchor the casing and pump the grout using a conventional, circulating pump

capable of moving the grout through the grout pipe to the bottom of the casing upward from the

bottom of the borehole. Using this procedure, the annular space between the sidewall of the

borehole and the casing will be filled from bottom to top in a uniform fashion displacing mud

and debris with minimum sidewall disturbance. Keep the casing anchored and allow the grout to

set before using the boreholes for crosshole testing. If shrinkage occurs near the mouth of the

borehole, additional grout should be inserted until the annular space is filled flush with the

ground surface.

Field Diagram:

Ray Diagram:

Seismic Record:

Results:

Depth Vp Vs ʋ ρ E G K

Equipment list for cross-hole seismic test

1. Freedom data PC with Wingeo software - 1 No.

2. Geophones - 2 Nos.

3. Dummy Probe - 3 Nos.

4. AC Charger - 1 No.

5. Car Battery Charger - 1 No.

6. P-SV Source - 1 No.

7. Manifold - 1 No.

8. Air Pump - 1 No.

9. Automatic Pump - 1 No.

10. Extension Board - 1 No.

11. Wire Bucket (Airline+Cable) with connectors - 3 Nos.

12. PC – Bucket Cable connectors - 7 +2 Nos.

13. Nylon rope - 3 Rolls

14. Nylon rope - 3 bundle (150 mtr)

15. Rope Clamp - 3 Nos.

16. Tool Box - 1 No.

17. Wireline - 3 No.

18. Accelerometer (3 Pieces including white wire) - 1 No.

19. Down hole Connection rod (1.5m) - 1 Nos.

(i) 1 Plyer, (ii) 2 Screwdrivers, (iii) 1 Hexa Blade, (iv) 1 Cutter, (v)

10 Insulation tapes, (vi) 3 Teflon Tapes, (vii) 4 Rubber caps, (viii) 1

Measuring tape, (ix) 1 Marker Pen, (x) 1 Scissor, (xi) LN Key

Spanner set, (xii) 1 Spanner 12/13, (xiii) source Spacers (xiv)

Geophone Spacers, (xv) Racing cycle tubes (xvi) Varnier caliper,

(xvii) Cycle tube solution, (xviii) Various types of Screws, (xix) Source

air pipe fennels, (xx) Motorcycle wheel adapter (xxi) Silicon grease

4. Conclusion:

Application of Seismic refraction survey (LVL and Up-hole):

1. Stratigraphic mapping

2. Estimation of depth to bedrock

3. Estimation of depth to water table

4. Predicting the rippability of specific rock types

5. Locating sinkholes

6. Landfill investigations

7. Geotechnical investigations

8. Static correction in seismic reflection survey (Petroleum Exploration) or deep seismic

Application of Cross-hole Seismic survey (Building Construction):

1. Determine the dynamic soil properties as a function of depth.

2. Define the advantages and disadvantages of each method in relation to local site

characteristics.

3. Correlate and Compare the result between the different methods in order to validate the

modeling results.

4. Propose predictive equation models for the assessment of Vs based on the geophysical

methods and geotechnical parameters.

4.1 Geo-technical parameters:

Shear Modulus (G):G= ρVs2

Young Modulus (E):E=2G(1+ ʋ)

Bulk Modulus (K):K=(1/3)*[E/(1-2ʋ)]

Poisson’s ratio (ʋ):ʋ=0.5[(Vp / Vs)

2-2]/ [(Vp

/ Vs)

2-1]

These parameters are useful in identification of basement for the purpose of Industry, Building,

Bridge and Highway constructions.

References:

Reynolds, J.M. 2011 An Introduction to Applied and Environmental Geophysics John Wiley &

Sons Ltd, Chichester, 2nd ed.

Dobrin MB (1983). Introduction to Geophysical Prospecting. McGraw–Hill: New York, NY.

Hospers J (1965).

A comparison of shear wave velocities obtained from the Crosshole seismic, spectral analysis of

surface waves and Multiple impacts of surface waves methods: Patrick K. Miller, Olson

Engineering, Wheat Ridge, CO, Nils Ryden, Lund University, Lund, SE, Yajai Tinkey, Olson

Engineering, Wheat Ridge, CO, Larry D. Olson, Olson Engineering, Wheat Ridge, CO.

Near-Surface Seismic Refraction Surveying Field Methods: Deborah Underwood, Geometrics,

Inc.

Burger, H. R., Exploration Geophysics of the Shallow Subsurface, Prentice Hall P T R, 1992.

Robinson and C. Coruh, Basic Exploration Geophysics, John Wiley, 1988.

Telford, W. M., L. P. Geldart, and R. E. Sheriff, Applied Geophysics, 2nd ed. Cambridge

University Press, 1990.

An introduction to refraction seismology, course notes describing the principles of refraction

seismology.

Definition from the Encyclopedic Dictionary of Exploration Geophysics by R. E. Sheriff,

published by the Society of Exploration Geophysics.

Seismic waves and earthquake location J.R. Kayal Geological Survey of India,