scholarly journals Strength-Based and Wave-Based Liquefaction Characterization

2006 ◽  
Vol 321-323 ◽  
pp. 1403-1406
Author(s):  
Gye Chun Cho ◽  
Jong Sub Lee
Keyword(s):  
Shear Strength ◽  
Wave Reflection ◽  
Spatial Scales ◽  
P Wave ◽  
Excess Pore Pressure ◽  
Soil Mechanic ◽  
S Wave ◽  
Before And After ◽  
Comprehensive Picture ◽  
Deep Layers

The purposes of this study are to analyze post liquefaction shear strength and to explore the potential use of wave-based techniques to monitor liquefaction and post liquefaction response. The first part presents a detailed analysis of triaxial test results to identify robust strength criteria. The second part documents experimental data on the characterization of liquefaction events with P-wave reflection imaging and S-wave trans-illumination techniques. The relevance of multiple coexisting temporal and spatial scales is highlighted. The following results are obtained: 1) the post liquefaction shear strength can be estimated within the framework of critical state soil mechanic; 2) the P-wave reflection images obtained before and after liquefaction represent the depression of the soil-water interface; 3) excess pore pressure migration from liquefied deep layers may cause zero-effective stress in dilative shallow layers. P-wave reflection is a valuable tool to monitor the evolution of subsurface structures and S-wave trans-illumination technique can be used to yield a comprehensive picture of the spatial evolution of liquefaction.

scholarly journals Determination of vp/vs on Bali Province: Case of Bali Earthquake March 22, 2017

2018 ◽  
Vol 19 (2) ◽  
pp. 73
Author(s):  
Febi Niswatul Auliyah ◽  
Komang Ngurah Suarbawa ◽  
Indira Indira
Keyword(s):  
Case Studies ◽  
Wave Velocity ◽  
P Wave ◽  
S Wave ◽  
Diagram Method ◽  
P Wave Velocity ◽  
Before And After ◽  
Earthquake Data

P-wave velocity and S-wave velocity have been investigated in the Bali Province by using earthquake case studies on March 22, 2017. The study was focused on finding out whether there were anomalies in the values of vp/vs before and after the earthquake. Earthquake data was obtained from the Meteorology, Climatology and Geophysics Agency (BMKG) Region III Denpasar, which consisted of the main earthquake on March 22, 2017 and earthquake data in August 2016 to May 2017. Data was processed using the wadati diagram method, obtained that the vp/vs on SRBI, IGBI, DNP and RTBI stations are shifted from 1.5062 to 1.8261. Before the earthquake occurred the anomaly of the value of vp/vs was found on the four stations, at the SRBI station at 10.35%, at the IGBI station at 16.16%, at DNP station at 12.27% and at RTBI station at 4.62%.

Low‐cost geophysical investigations of a paleochannel aquifer in the Eastern Goldfields, Western Australia

Geophysics ◽  
2002 ◽  
Vol 67 (3) ◽  
pp. 690-700 ◽  
Author(s):  
Josef Holzschuh
Keyword(s):  
Water Table ◽  
Western Australia ◽  
Seismic Reflection ◽  
Wave Reflection ◽  
Gravity Data ◽  
P Wave ◽  
Gravity Modeling ◽  
S Wave ◽  
Sand And Gravel ◽  
Gravel Aquifer

Compressional (P) wave and shear (S) wave seismic reflection techniques were used to delineate the sand and gravel aquifer within a highly saline clay‐filled paleochannel in the Eastern Goldfields of Western Australia. The seismic refraction and gravity methods were also used to investigate the paleochannel. The unsaturated loose fine‐grained sand up to 10 m in depth at the surface is a major factor in degrading subsurface imaging. The seismic processing needed to be precise, with accurate static corrections and normal moveout corrections. Deconvolution enhanced the aquifer and other paleochannel reflectors. P‐wave reflection and refraction layer depths had good correlation and showed a total of six boundaries: (1) water table, (2) change in velocity (compaction) in the paleochannel sediments, (3) sand and gravel aquifer, (4) red‐brown saprolite and green saprolite boundary, (5) weathered bedrock, and (6) unweathered bedrock. P‐wave explosive and hammer sources were found to have similar signal characteristics, and the aquifer and bedrock were both imaged using the hammer source. The deep shots below the water table have the most broadband frequency response for reflections, but stacking clear reflections was difficult. The S‐wave reflection results showed high lateral and vertical resolution of the basal saprolite clay, the sand and gravel aquifer, and very shallow clays above the aquifer. The S‐wave reflection stacking velocities were 10–20% of the P‐waves, increasing the resolution of the S‐wave section. The gravity data were modelled to fit the known drilling and P‐wave seismic reflection depths. The refraction results did not identify the top of bedrock, so refraction depths were not used for the gravity modeling in this highly weathered environment. The final gravity model mapped the bedrock topography beyond the lateral extent of the seismic and drilling data.

Two-step joint PP- and PS-wave three-term amplitude-variation with offset inversion

2016 ◽  
Vol 4 (4) ◽  
pp. T613-T625 ◽  
Author(s):  
Qizhen Du ◽  
Bo Zhang ◽  
Xianjun Meng ◽  
Chengfeng Guo ◽  
Gang Chen ◽  
...  
Keyword(s):  
Reflection Coefficient ◽  
Wave Reflection ◽  
Coefficient Matrix ◽  
P Wave ◽  
Inversion Method ◽  
S Wave ◽  
Amplitude Variation ◽  
Amplitude Variation With Offset ◽  
Avo Inversion ◽  
Pp Wave

Three-term amplitude-variation with offset (AVO) inversion generally suffers from instability when there is limited prior geologic or petrophysical constraints. Two-term AVO inversion shows higher instability compared with three-term AVO inversion. However, density, which is important in the fluid-type estimation, cannot be recovered from two-term AVO inversion. To reliably predict the P- and S-waves and density, we have developed a robust two-step joint PP- and PS-wave three-term AVO-inversion method. Our inversion workflow consists of two steps. The first step is to estimate the P- and S-wave reflectivities using Stewart’s joint two-term PP- and PS-AVO inversion. The second step is to treat the P-wave reflectivity obtained from the first step as the prior constraint to remove the P-wave velocity related-term from the three-term Aki-Richards PP-wave approximated reflection coefficient equation, and then the reduced PP-wave reflection coefficient equation is combined with the PS-wave reflection coefficient equation to estimate the S-wave and density reflectivities. We determined the effectiveness of our method by first applying it to synthetic models and then to field data. We also analyzed the condition number of the coefficient matrix to illustrate the stability of the proposed method. The estimated results using proposed method are superior to those obtained from three-term AVO inversion.

High-resolution P- and S-wave Seismic Reflection Followed by Engineering Modeling for Geotechnical Site Characterization in Southern Illinois

2017 ◽  
Vol 22 (4) ◽  
pp. 375-384
Author(s):  
Ahmed Ismail ◽  
Adel Abdelnaby ◽  
Timothy Larson
Keyword(s):  
High Resolution ◽  
Seismic Reflection ◽  
Wave Reflection ◽  
P Wave ◽  
S Wave ◽  
Southern Illinois ◽  
Mine Subsidence ◽  
Land Sliding ◽  
Seismic Reflection Profiles ◽  
Engineering Modeling

A study was conducted to determine whether the structural failure of a house in a residential subdivision in southern Illinois was caused by the collapse of an old underground coal mine ( i.e. mine subsidence) or as a result of a landslide. The house was displaced approximately 5 m downhill towards an engineered lake behind it. To detect any old mines near the house, we acquired high-resolution S-wave seismic reflection profiles along the roads surrounding the subdivision and a series of high-resolution P-wave reflection profiles in the immediate vicinity of the house. The S-wave seismic reflection profiles imaged a strong shallow horizon that we interpreted as Pennsylvanian siltstone overlying the Mecca Quarry Shale and Colchester Coal, which had been previously mined in the area. Locally, this horizon showed no evidence of any recent mining activities. The high-resolution P-wave reflection profiles imaged a steeply dipping bedrock with a 20° dip at the house location. These results exclude mine subsidence from being the cause for the house failure. To investigate land sliding as a possible cause of the house failure, depths to bedrock from the seismic results together with the soil type information were used to model the soil materials with a Mohr-Coulomb stress-strain model. The engineering model demonstrated that a land slide is a more plausible cause for the house failure, which agrees with the seismic results.

Direct hydrocarbon detection using comparative P-wave and S-wave seismic sections

Geophysics ◽  
1985 ◽  
Vol 50 (3) ◽  
pp. 383-393 ◽  
Author(s):  
James D. Robertson ◽  
William C. Pritchett
Keyword(s):  
River Basin ◽  
Wave Velocity ◽  
Field Experiments ◽  
Wave Reflection ◽  
P Wave ◽  
Bright Spot ◽  
S Wave ◽  
Green River Basin ◽  
Green River ◽  
Seismic Sections

Two field experiments in the Sacramento basin and one in the Green River basin demonstrate that comparative P-wave and S-wave CDP seismic sections can be used to detect gas directly in sandstone reservoirs. The lines in the Sacramento basin were shot over producing gas fields known to correlate with amplitude anomalies on P-wave sections. Reflections of comparable strength are present on the P-wave and S-wave sections at lithologic boundaries, but gas‐saturated zones correlating with P-wave bright spots show no equivalent S-wave amplitude anomalies. The responses are consistent with laboratory observations that P-wave velocity is more sensitive to the introduction of gas into liquid‐saturated pore space than S-wave velocity. The line in the Green River basin was shot over a relatively deep gas field producing from an overpressured reservoir not associated with a conventional P-wave bright spot. The P-wave reflection strength of the reservoir is about 50 percent greater than the S-wave reflection strength, whereas the P and S strengths of other major reflectors are comparable. The three field tests show that an S-wave section validates a P-wave bright spot attributed to gas saturation when there is no anomalous amplitude at the equivalent S-wave event and that the technique is useful for verification of subtle as well as strong amplitude anomalies.

Determining fast-S and slow-S propagation directions with SV-P data produced by buried explosives and recorded with vertical geophones

2021 ◽  
Vol 9 (2) ◽  
pp. T599-T609
Author(s):  
Bob Hardage ◽  
Mike Graul ◽  
Tim Hall ◽  
Chris Hall ◽  
Mark Kelley ◽  
...  
Keyword(s):  
Wave Reflection ◽  
Pore Space ◽  
Horizontal Stress ◽  
Wave Mode ◽  
P Wave ◽  
S Wave ◽  
Wave Source ◽  
Wave Imaging ◽  
Almost All ◽  
Maximum Horizontal Stress

We have evaluated the concept of practicing S-wave reflection seismology with legacy 3D seismic data generated by a P-wave source and recorded with only vertical geophones. This type of S-wave imaging is based on the principle that seismic P-wave sources not only produce a downgoing illuminating P wavefield, but they also simultaneously produce a downgoing illuminating SV wavefield that, in almost all cases, is suitable for S-wave reflection imaging. The S-mode used in this study is the SV-P, or converted-P, mode. This mode involves a downgoing illuminating SV wavefield and an upgoing reflected P-mode that is recorded by vertical geophones. In flat-layered stratigraphy, the lengths of the SV and P raypaths in SV-P imaging are identical to the lengths of the SV and P raypaths in P-SV imaging with P-sources and 3C geophones. P-SV imaging of deep rocks has been practiced for more than two decades; SV-P imaging is a new concept. SV-P data should provide the same options for investigating deep rocks as do P-SV data. We have determined one of the equivalences between SV-P data extracted from vertical-geophone data and P-SV data extracted from horizontal geophones: that both modes react to azimuth-dependent variations in the S velocity in anisotropic rocks. Azimuthal variations in the SV-P traveltime can be used to define the polarization direction of the fast-S-wave mode, which is also the azimuth of the maximum horizontal stress (SHmax). Our investigation demonstrates a noninvasive method for monitoring changes in the SHmax azimuth across a CO2 storage reservoir, or any targeted porous rock, as fluids are cycled into, and then out of, that rock’s pore space.

Compressional and shear‐wave logging in open and cased holes using a multipole tool

Geophysics ◽  
1991 ◽  
Vol 56 (4) ◽  
pp. 550-557 ◽  
Author(s):  
S. T. Chen ◽  
E. A. Eriksen
Keyword(s):  
P Wave ◽  
Log P ◽  
S Wave ◽  
S Waves ◽  
System P ◽  
Receiver System ◽  
Wide Range ◽  
Before And After ◽  
Sonic Logging ◽  
Logging Tool

We have found in field observations that the multipole sonic logging tool can effectively measure formation P‐wave and S‐wave data in a cased hole. The multipole tool, containing both monopole and quadrupole source‐receiver systems, was originally designed to log P‐ and S‐waves directly, in all lithologies, for an open borehole. The monopole source‐receiver system (P‐wave) operates at 7–10 kHz, as compared with 15–25 kHz for a conventional sonic tool, while the quadrupole source‐receiver system (S‐wave) operates at 3–7 kHz. These lower operating frequencies enable the signals to penetrate the well casing and cement more effectively than signals from a conventional sonic tool. As a result, the formation P‐ and S‐waves recorded by the multipole tool are generally much stronger than the unwanted waves which travel along the well casing and cement. Formation arrivals can be easily identified and separated from the casing arrivals for a wide range of lithologies. Logs run before and after the wells were cased show remarkable agreement even in severely washed out zones.

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