Delineation of geologic contacts by seismic refraction with application to the fault zone between the Thompson nickel belt and the Churchill Tectonic Province

1980 ◽  
Vol 17 (9) ◽  
pp. 1141-1151 ◽  
Author(s):  
A. G. Green
Keyword(s):  
Fault Zone ◽  
Delay Time ◽  
Wave Attenuation ◽  
Seismic Refraction ◽  
P Wave ◽  
S Wave ◽  
Wave Velocities ◽  
P Wave Velocities ◽  
A New Technique ◽  
The Times

Refracted P-wave and S-wave arrivals are studied from a fourfold multicoverage seismic experiment that has been conducted across a region that spans the contact between the Thompson nickel belt and the Churchill Province in northern Manitoba. A new technique for the calculation of accurate delay times and basement velocities for unreversed multicoverage data is introduced. In this technique, the times of rays between selected shots and receivers are combined to give initial delay time corrections and a subsequent iterative least-squares analysis yields the final delay time corrections and estimates of the basement P-wave velocities. The P-wave velocities correlate well with the basement geology and have been used to refine the location of the contact between the Moak Lake gneisses of the Thompson nickel belt and the Kisseynew gneisses of the Churchill Province. From the P-wave velocities and S-wave attenuation it is concluded that this contact is a fault zone.

scholarly journals A method of geo-acoustic parameter inversion in shallow sea by the Bayesian theory and the acoustic pressure field

2019 ◽  
Vol 283 ◽  
pp. 06003
Author(s):  
Guangxue Zheng ◽  
Hanhao Zhu ◽  
Jun Zhu
Keyword(s):  
Sound Pressure ◽  
Pressure Field ◽  
Wave Attenuation ◽  
Acoustic Parameter ◽  
Bayesian Theory ◽  
P Wave ◽  
Shallow Sea ◽  
S Wave ◽  
Wave Velocities ◽  
Parameter Inversion

A method of geo-acoustic parameter inversion based on the Bayesian theory is proposed for the acquisition of acoustic parameters in shallow sea with the elastic seabed. Firstly, the theoretical prediction value of the sound pressure field is calculated by the fast field method (FFM). According to the Bayesian theory, we establish the misfit function between the measured sound pressure field and the theoretical pressure field. It is under the assumption of Gaussian data errors which are in line with the likelihood function. Finally, the posterior probability density (PPD) of parameters is given as the result of inversion. Our research is conducted in the light of Metropolis sample rules. Apart from numerical simulations, a scaled model experiment has been taken in the laboratory tank. The results of numerical simulations and tank experiments show that sound pressure field calculated by the result of inversion is consistent with the measured sound pressure field. Besides, s-wave velocities, p-wave velocities and seafloor density have fewer uncertainties and are more sensitive to complex sound pressure than s-wave attenuation and p-wave attenuation. The received signals calculated by inversion results are keeping with received signals in the experiment which verify the effectiveness of this method.

Dispersion patterns of the ground roll in eastern Saudi Arabia

Geophysics ◽  
1981 ◽  
Vol 46 (2) ◽  
pp. 121-137 ◽  
Author(s):  
Moujahed I. Al‐Husseini ◽  
Jon B. Glover ◽  
Brian J. Barley
Keyword(s):  
Saudi Arabia ◽  
Rayleigh Wave ◽  
Wavelength Range ◽  
Noise Analysis ◽  
Regional Scale ◽  
P Wave ◽  
S Wave ◽  
Wave Velocities ◽  
Ground Roll ◽  
P Wave Velocities

Seismic surveys on land must be designed so that the source‐generated noise, such as ground roll, is preferentially attenuated before P‐wave signal amplification and recording. The correct specification of spatial and frequency filters requires prior knowledge of the noise properties in the area. We show that the strong Rayleigh wave component of source‐generated noise has a wavelength range which is predictable on a regional scale, using widespread P‐wave velocity measurements in shallow upholes. This predictive capability decreases the number of noise analyses required to map the boundaries between areas with different Rayleigh wave properties. The case history presented is for northeastern Saudi Arabia, an area of roughly [Formula: see text]. The data comprise 80 noise analyses and a data base of over 10,000 up‐hole measurements of P‐wave velocities, supplemented by maps of topography and geologic outcrops. Examples show that the frequency‐wavenumber transforms of time‐offset records can be interpreted in detail in terms of Rayleigh wave dispersion and air wave coupling, dictated by the elastic properties of the very shallow layers. P‐wave velocities, measured in shallow upholes at noise analysis sites, are used to form initial estimates of the corresponding shear‐wave velocities and subsequently refined by matching the observed and predicted dispersion curves. Even without this refinement process, the initial S‐wave velocities can be used to estimate Rayleigh wave velocities at frequencies which typify the top and bottom of current vibrator sweeps (10 and 80 Hz). These velocities are mapped for the area and used to determine the wavelength range of Rayleigh waves. An effort is also made to map regions where Rayleigh wave scattering from surface topography is likely to occur.

S-wave velocity measurements in deep soil deposit and bedrock by means of an elaborated down-hole method

1980 ◽  
Vol 70 (1) ◽  
pp. 363-377
Author(s):  
Y. Ohta ◽  
N. Goto ◽  
F. Yamamizu ◽  
H. Takahashi
Keyword(s):  
Wave Velocity ◽  
Earthquake Engineering ◽  
Underground Structure ◽  
P Wave ◽  
Velocity Measurements ◽  
S Wave ◽  
Deep Soil ◽  
Tokyo Metropolitan Area ◽  
Wave Velocities ◽  
P Wave Velocities

abstract Deep S-wave velocity measurements were planned at two separate sites in the Tokyo area from the earthquake engineering point of view, and actually carried out down to 2 to 3 km in depth using geophysical observation wells. S-waves were produced by means of ordinary small explosions and a specially designed SH-wave generator. A set of three component seismometers was installed in a capsule having a device that is clamped to the borehole wall. Measurements to the bottom of the wells were conducted at about 15 different depths at intervals of 100 to 500 m. The S-wave velocities are around 0.8 km/sec in Pleistocene soils, 1.2 to 1.6 km/sec in Miocene soils, and 2.5 to 2.7 km/sec in Cambrian rocks. The corresponding P-wave velocities are 2.0 to 2.3 km/sec, 2.6 to 3.0 km/sec, and 4.7 to 4.9 km/sec, respectively. These data show both S- and P-wave velocities in deep soil deposit increasing with depth. The greatest velocity difference is at the boundary above the pre-Tertiary rocks. The velocity structures completely agree with the known data such as sonic logs, density distributions, and geological sections. A comparison with velocity profiles at two separate sites was also made as the first step to visualize the three-dimensional underground structure in the Tokyo metropolitan area. The seismological and earthquake engineering importance of shear-wave velocity measurements for thick soil deposits was demonstrated by approximate calculations of the amplification of seismic waves between ground surface and bedrock.

Pore pressure prediction from S‐wave, C‐wave, and P‐wave velocities

2003 ◽  
Author(s):  
Dan Ebrom ◽  
Phil Heppard ◽  
Mike Mueller ◽  
Leon Thomsen
Keyword(s):  
Pore Pressure ◽  
P Wave ◽  
S Wave ◽  
Wave Velocities ◽  
Pore Pressure Prediction ◽  
P Wave Velocities

P- and S-wave attenuation logs from monopole sonic data

Geophysics ◽  
2000 ◽  
Vol 65 (3) ◽  
pp. 755-765 ◽  
Author(s):  
Xinhua Sun ◽  
Xiaoming Tang ◽  
C. H. (Arthur) Cheng ◽  
L. Neil Frazer
Keyword(s):  
Wave Attenuation ◽  
Fluid Velocity ◽  
P Wave ◽  
Reservoir Rock ◽  
Rock Properties ◽  
S Wave ◽  
Intrinsic Attenuation ◽  
Modified Method ◽  
Receiver Array ◽  
Attenuation Profiles

In this paper, a modification of an existing method for estimating relative P-wave attenuation is proposed. By generating synthetic waveforms without attenuation, the variation of geometrical spreading related to changes in formation properties with depth can be accounted for. With the modified method, reliable P- and S-wave attenuation logs can be extracted from monopole array acoustic waveform log data. Synthetic tests show that the P- and S-wave attenuation values estimated from synthetic waveforms agree well with their respective model values. In‐situ P- and S-wave attenuation profiles provide valuable information about reservoir rock properties. Field data processing results show that this method gives robust estimates of intrinsic attenuation. The attenuation profiles calculated independently from each waveform of an eight‐receiver array are consistent with one another. In fast formations where S-wave velocity exceeds the borehole fluid velocity, both P-wave attenuation ([Formula: see text]) and S-wave attenuation ([Formula: see text]) profiles can be obtained. P- and S-wave attenuation profiles and their comparisons are presented for three reservoirs. Their correlations with formation lithology, permeability, and fractures are also presented.

GEOTECHNICAL PARAMETERS STUDY USING SEISMIC REFRACTION TOMOGRAPHY

2016 ◽  
Vol 78 (8-6) ◽  
Author(s):  
Rose Nadia ◽  
Rosli Saad ◽  
Nordiana Muztaza ◽  
Nur Azwin Ismail ◽  
Mohd Mokhtar Saidin
Keyword(s):  
Parameter Estimation ◽  
Seismic Refraction ◽  
Standard Penetration Test ◽  
P Wave ◽  
Cohesive Soils ◽  
Penetration Test ◽  
Geotechnical Parameters ◽  
Wave Velocities ◽  
Refraction Tomography ◽  
Loose Medium

In this study, correlation is made between seismic P-wave velocities (Vp) with standard penetration test (SPT-N) values to produce soil parameter estimation for engineering site applications. A seismic refraction tomography (SRT) line of 69 m length was spread across two boreholes with 3 m geophones spacing. The acquired data were processed using Firstpix, SeisOpt2D and surfer8 software. The Vp at particular depths were pinpointed and correlated with geotechnical parameters (SPT-N values) from the borehole records. The correlation between Vp and SPT-N values has been established. For cohesive soils, it is grouped into three categories according to consistencies; stiff, very stiff and hard, having velocity rangesof 575-314 m/s, 808-1483 m/s and 1735-2974 m/s, respectively. For non-cohesive soils, it is also divided into three categories based on the denseness as loose, medium dense and dense with Vp ranges of 528-622 m/s, 900-2846 m/s and 2876-2951 m/s, respectively

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