scholarly journals Generalized Pattern Search Algorithm for Crustal Modeling

Computation ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 105
Author(s):  
Mulugeta Dugda ◽  
Farzad Moazzami
Keyword(s):  
Simultaneous Determination ◽  
Wave Velocity ◽  
Seismic Station ◽  
Receiver Functions ◽  
Pattern Search ◽  
P Wave ◽  
Computational Time ◽  
Rift System ◽  
Generalized Pattern Search

In computational seismology, receiver functions represent the impulse response for the earth structure beneath a seismic station and, in general, these are functionals that show several seismic phases in the time-domain related to discontinuities within the crust and the upper mantle. This paper introduces a new technique called generalized pattern search (GPS) for inverting receiver functions to obtain the depth of the crust–mantle discontinuity, i.e., the crustal thickness H, and the ratio of crustal P-wave velocity Vp to S-wave velocity Vs. In particular, the GPS technique, which is a direct search method, does not need derivative or directional vector information. Moreover, the technique allows simultaneous determination of the weights needed for the converted and reverberated phases. Compared to previously introduced variable weights approaches for inverting H-κ stacking of receiver functions, with κ = Vp/Vs, the GPS technique has some advantages in terms of saving computational time and also suitability for simultaneous determination of crustal parameters and associated weights. Finally, the technique is tested using seismic data from the East Africa Rift System and it provides results that are consistent with previously published studies.

Constraining crustal structure in the presence of sediment: a multiple converted wave approach

2019 ◽  
Vol 219 (1) ◽  
pp. 313-327 ◽  
Author(s):  
Erin Cunningham ◽  
Vedran Lekic
Keyword(s):  
Wave Velocity ◽  
Seismic Velocity ◽  
Seismic Station ◽  
Sedimentary Basins ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
P Wave ◽  
Converted Wave ◽  
P Wave Velocity ◽  
Multiple Data Sets

SUMMARY Receiver functions are sensitive to sharp seismic velocity variations with depth and are commonly used to constrain crustal thickness. The H–κ stacking method of Zhu & Kanamori is often used to constrain both the crustal thickness (H) and ${V_P}$/${V_S}$ ratio ($\kappa $) beneath a seismic station using P-to-s converted waves (Ps). However, traditional H–κ stacks require an assumption of average crustal velocity (usually ${V_P}$). Additionally, large amplitude reverberations from low velocity shallow layers, such as sedimentary basins, can overprint sought-after crustal signals, rendering traditional H–$\ \kappa $ stacking uninterpretable. We overcome these difficulties in two ways. When S-wave reverberations from sediment are present, they are removed by applying a resonance removal filter allowing crustal signals to be clarified and interpreted. We also combine complementary Ps receiver functions, Sp receiver functions, and the post-critical P-wave reflection from the Moho (SPmp) to remove the dependence on an assumed average crustal ${V_P}$. By correcting for sediment and combining multiple data sets, the crustal thickness, average crustal P-wave velocity and crustal ${V_P}$/${V_S}$ ratio is constrained in geological regions where traditional H–$\ \kappa $ stacking fails, without making an initial P-wave velocity assumption or suffering from contamination by sedimentary reverberations.

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%.

Shallow Shear-Wave Velocity Structure in Oklahoma Based on the Joint Inversion of Ambient Noise Dispersion and Teleseismic P-Wave Receiver Functions

2020 ◽  
Author(s):  
Jiayan Tan ◽  
Charles A. Langston ◽  
Sidao Ni
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Ambient Noise ◽  
Sedimentary Basins ◽  
Velocity Model ◽  
Receiver Functions ◽  
P Wave ◽  
Velocity Models

ABSTRACT Ambient noise cross-correlations, used to obtain fundamental-mode Rayleigh-wave group velocity estimates, and teleseismic P-wave receiver functions are jointly modeled to obtain a 3D shear-wave velocity model for the crust and upper mantle of Oklahoma. Broadband data from 82 stations of EarthScope Transportable Array, the U.S. National Seismic Network, and the Oklahoma Geological Survey are used. The period range for surface-wave ambient noise Green’s functions is from 4.5 to 30.5 s constraining shear-wave velocity to a depth of 50 km. We also compute high-frequency receiver functions at these stations from 214 teleseismic earthquakes to constrain individual 1D velocity models inferred from the surface-wave tomography. Receiver functions reveal Ps conversions from the Moho, intracrustal interfaces, and shallow sedimentary basins. Shallow low-velocity zones in the model correlate with the large sedimentary basins of Oklahoma. The velocity model significantly improves the agreement of synthetic and observed seismograms from the 6 November 2011 Mw 5.7 Prague, Oklahoma earthquake suggesting that it can be used to improve earthquake location and moment tensor inversion of local and regional earthquakes.

scholarly journals Deep-towed high resolution seismic imaging II: Determination of P-wave velocity distribution

2018 ◽  
Vol 132 ◽  
pp. 29-36 ◽  
Author(s):  
B. Marsset ◽  
S. Ker ◽  
Y. Thomas ◽  
F. Colin
Keyword(s):  
High Resolution ◽  
Velocity Distribution ◽  
Wave Velocity ◽  
Seismic Imaging ◽  
P Wave ◽  
P Wave Velocity

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

Simultaneous determination of wave velocity and thickness on overlapped signals using Forward Backward algorithm

2017 ◽  
Vol 86 ◽  
pp. 100-105 ◽  
Author(s):  
J. Bustillo ◽  
H. Achdjian ◽  
A. Arciniegas ◽  
L. Blanc
Keyword(s):  
Simultaneous Determination ◽  
Wave Velocity

scholarly journals Bayesian inversion of non-sonic well log data for the determination of P-wave velocity - application to data from Jequitinhonha Basin, Brazil

2016 ◽  
Author(s):  
Odette Caroline Aquino Aragão ◽  
Amin Bassrei ◽  
Geraldo Girão Nery
Keyword(s):  
Wave Velocity ◽  
P Wave ◽  
Bayesian Inversion ◽  
Well Log ◽  
Log Data ◽  
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
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