scholarly journals Determination of P-Wave Velocity Structures, Earthquake Hypocenters, and Focal Mechanisms in the Morgan Hill Region of Central California

2000 ◽  
Vol 11 (4) ◽  
pp. 929 ◽  
Author(s):  
Cheng-Horng Lin ◽  
Steven W. Roecker
Keyword(s):  
Wave Velocity ◽  
Focal Mechanisms ◽  
P Wave ◽  
Central California ◽  
Hill Region ◽  
P Wave Velocity

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%.

Determining P- and S-wave velocities and Q-values from single ultrasound transmission measurements performed on cylindrical rock samples: it’s possible, when…

2020 ◽  
Author(s):  
Marc S. Boxberg ◽  
Mandy Duda ◽  
Katrin Löer ◽  
Wolfgang Friederich ◽  
Jörg Renner
Keyword(s):  
Wave Velocity ◽  
P Wave ◽  
S Wave ◽  
Standard Material ◽  
Rock Samples ◽  
Intrinsic Attenuation ◽  
Finite Element Software ◽  
Wave Velocities ◽  
P Wave Velocity

<p>Determining elastic wave velocities and intrinsic attenuation of cylindrical rock samples by transmission of ultrasound signals appears to be a simple experimental task, which is performed routinely in a range of geoscientific and engineering applications requiring characterization of rocks in field and laboratory. P- and S-wave velocities are generally determined from first arrivals of signals excited by specifically designed transducers. A couple of methods exist for determining the intrinsic attenuation, most of them relying either on a comparison between the sample under investigation and a standard material or on investigating the same material for various geometries.</p><p>Of the three properties of interest, P-wave velocity is certainly the least challenging one to determine, but dispersion phenomena lead to complications with the consistent identification of frequency-dependent first breaks. The determination of S-wave velocities is even more hampered by converted waves interfering with the S-wave arrival. Attenuation estimates are generally subject to higher uncertainties than velocity measurements due to the high sensitivity of amplitudes to experimental procedures. The achievable accuracy of determining S-wave velocity and intrinsic attenuation using standard procedures thus appears to be limited.</p><p>We pursue the determination of velocity and attenuation of rock samples based on full waveform modeling and inversion. Assuming the rock sample to be homogeneous - an assumption also underlying standard analyses - we quantify P-wave velocity, S-wave velocity and intrinsic P- and S-wave attenuation from matching a single ultrasound trace with a synthetic one numerically modelled using the spectral finite-element software packages SPECFEM2D and SPECFEM3D. We find that enough information on both velocities is contained in the recognizable reflected and converted phases even when nominal P-wave sensors are used. Attenuation characteristics are also inherently contained in the relative amplitudes of these phases due to their different travel paths. We present recommendations for and results from laboratory measurements on cylindrical samples of aluminum and rocks with different geometries that we also compare with various standard analysis methods. The effort put into processing for our approach is particularly justified when accurate values and/or small variations, for example in response to changing P-T-conditions, are of interest or when the amount of sample material is limited.</p>

Determination of P-wave Velocity of Carbonate Building Stones During Freeze–Thaw Cycles

2020 ◽  
Vol 38 (6) ◽  
pp. 5999-6009
Author(s):  
Vahid Amirkiyaei ◽  
Ebrahim Ghasemi ◽  
Lohrasb Faramarzi
Keyword(s):  
Wave Velocity ◽  
P Wave ◽  
Building Stones ◽  
Freeze Thaw ◽  
P Wave Velocity

Combined TDR and P-Wave Velocity Measurements for the Determination of In Situ Soil Density—Experimental Study

2005 ◽  
Vol 28 (6) ◽  
pp. 12293 ◽  
Author(s):  
L David Suits ◽  
TC Sheahan ◽  
D Fratta ◽  
KA Alshibli ◽  
WM Tanner ◽  
...  
Keyword(s):  
Experimental Study ◽  
Wave Velocity ◽  
P Wave ◽  
Soil Density ◽  
Velocity Measurements ◽  
P Wave Velocity

Determination of fracture depth of rock blocks from P-wave velocity

2007 ◽  
Vol 67 (1) ◽  
pp. 11-16 ◽  
Author(s):  
S. Kahraman ◽  
M. Soylemez ◽  
M. Fener
Keyword(s):  
Wave Velocity ◽  
P Wave ◽  
P Wave Velocity

scholarly journals A robust experimental determination of Thomsen’s δ parameter

Geophysics ◽  
2015 ◽  
Vol 80 (1) ◽  
pp. A19-A24 ◽  
Author(s):  
Joel Sarout ◽  
Claudio Delle Piane ◽  
Dariush Nadri ◽  
Lionel Esteban ◽  
David N. Dewhurst
Keyword(s):  
Wave Velocity ◽  
Traditional Method ◽  
Anisotropy Parameter ◽  
P Wave ◽  
New Method ◽  
Inversion Method ◽  
Velocity Measurements ◽  
Significant Discrepancy ◽  
P Wave Velocity

A novel inversion method for the laboratory determination of Thomsen’s [Formula: see text] anisotropy parameter on cylindrical rock specimens from ultrasonic data has been recently reported in the literature. We further assessed this method through a direct comparison of the results of the traditional method (involving a single off-axis P-wave velocity measurement at 45°) and the new method (involving 65 P-wave velocity measurements at several angles to the symmetry axis). We prepared and characterized two vertical shale specimens from the same preserved vertical core to assess their similarity in terms of structure, mineralogy, porosity, and density. The shale was assumed to be transversely isotropic in view of the observed (horizontal) bedding. We subjected both specimens to the same brine saturation and effective stress state. Using the two methods, we obtained similar results for Thomsen’s [Formula: see text] (vertical P-wave) and [Formula: see text] (P-wave anisotropy) parameters. However, a significant discrepancy was observed for Thomsen’s [Formula: see text] parameter: We obtained results of 0.13 using the new method and 0.39 using the traditional method. As a result of the overdetermined nature of the P-wave velocity measurements used in the new method, we believe that the corresponding [Formula: see text] value is more reliable. Also, the value derived with the new testing method seems to match more closely the reported field data.

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