scholarly journals Shear Velocity Structure Beneath Saudi Arabia From the Joint Inversion of P and S Wave Receiver Functions, and Rayleigh Wave Group Velocity Dispersion Data

2019 ◽  
Vol 124 (5) ◽  
pp. 4767-4787 ◽  
Author(s):  
Zheng Tang ◽  
P. Martin Mai ◽  
Jordi Julià ◽  
Hani Zahran
Keyword(s):  
Saudi Arabia ◽  
Velocity Dispersion ◽  
Velocity Structure ◽  
Group Velocity Dispersion ◽  
Joint Inversion ◽  
Shear Velocity ◽  
Receiver Functions ◽  
Wave Group ◽  
S Wave ◽  
Dispersion Data

One-dimensional Shear Velocity Structure of Northern Africa from Rayleigh Wave Group Velocity Dispersion

2001 ◽  
Vol 158 (8) ◽  
pp. 1475-1493 ◽  
Author(s):  
S. E. Hazler ◽  
A. F. Sheehan ◽  
D. E. McNamara ◽  
W. R. Walter
Keyword(s):  
Rayleigh Wave ◽  
Group Velocity ◽  
Velocity Dispersion ◽  
Velocity Structure ◽  
Group Velocity Dispersion ◽  
Shear Velocity ◽  
Northern Africa ◽  
Wave Group ◽  
One Dimensional

Lithospheric structure of the Arabian Shield from joint inversion of P- and S-wave receiver functions and dispersion velocities

2015 ◽  
Vol 65 (2) ◽  
pp. 239-255 ◽  
Author(s):  
Abdullah M. Al-Amri
Keyword(s):  
Green's Functions ◽  
Velocity Structure ◽  
Green’S Functions ◽  
Joint Inversion ◽  
Receiver Functions ◽  
Gulf Of Aqaba ◽  
Arabian Shield ◽  
S Wave ◽  
Velocity Models ◽  
Seismic Networks

Abstract New velocity models of lithospheric thickness and velocity structure have been developed for the Arabian Shield by three tasks: 1) Computing P-Wave Receiver Functions (PRFs) and S-Wave Receiver Functions (SRFs) for all the broadband stations within the Saudi seismic networks. The number of receiver function waveforms depends on the recording time window and quality of the broadband station. 2) Computing ambient noise correlation Green’s functions for all available station pairs within the Saudi seismic networks to image the shear velocity in the crust and uppermost mantle beneath the Arabian Peninsula. Together they provided hundreds of additional, unique paths exclusively sampling the region of interest. Both phase and group velocities for all the resulting empirical Green’s functions have been measured and to be used in the joint inversion. 3) Jointly inverted the PRFs and SRFs obtained in task 1 with dispersion velocities measured on the Green’s functions obtained in task 2 and with fundamental-mode, Rayleigh-wave, group and phase velocities borrowed from the tomographic studies to precisely determine 1D crustal velocity structure and upper mantle. The analysis of the PRFs revealed values of 25-45 km for crustal thickness, with the thin crust next to the Red Sea and Gulf of Aqaba and the thicker crust under the platform, and Vp/Vs ratios in the 1.70-1.80 range, suggesting a range of compositions (felsic to mafic) for the shield’s crust. The migrated SRFs suggest lithospheric thicknesses in the 80-100 km range for portions of the shield close to the Red Sea and Gulf of Aqaba and near the Arabian Gulf. Generally, the novelty of the velocity models developed under this paper has consisted in the addition of SRF data to extend the velocity models down to lithospheric and sub-lithospheric depths.

Crustal architecture of Amsterdam-St. Paul Island from an integrated geophysical approach

2021 ◽  
Author(s):  
Pankaj Kumar ◽  
Pratyush Anand ◽  
Dibakar Ghosal ◽  
Pabitra Singha
Keyword(s):  
Magnetic Material ◽  
Rayleigh Wave ◽  
Dispersion Curve ◽  
Group Velocity ◽  
Velocity Dispersion ◽  
Receiver Function ◽  
Group Velocity Dispersion ◽  
Joint Inversion ◽  
Wave Group ◽  
Magnetic Model

<p>The Amsterdam-St. Paul (ASP) island complex is a manifestation of interaction between the South-East Indian Ridge (SEIR) and the ASP mantle plume, which was formed ~10 Ma. Very few geophysical studies have been conducted over the ASP island complex and therefore we have limited information about the island so far. We performed an integrated geophysical approach using gravity, magnetic study along with the joint inversion of Ps receiver function and Rayleigh wave group velocity dispersion curve to determine the crustal architecture and Moho variation in the region. The result of integrated gravity-magnetic modeling revealed that the island complex is associated with three crustal layers beneath the sedimentary strata. Inversion of Rayleigh wave group velocity dispersion curve accounts for vertical shear wave velocity average which supported the layered velocity profile. The results revealed that magnetic material (Mid oceanic ridge basalt/Flood basalt) has carpeted the entire island causing high magnetic anomaly of -1000 to 1500 nT, which is generated by gradual accumulation of a thick pile of magnetic material of normal as well as reverse polarity. The results by integrated Gravity-magnetic model suggest that crust beneath the island is suggested to be highly affected by volcanic activity (Mantle Plume/Ridge) and is underlain by high-density underplated material. The results further suggest that SEIR has less role for the outpoured magmatic activity. Integrated Gravity-magnetic model show that Moho is variable beneath the island complex and lies in the range of ~12-17 km. Further results by joint inversion of Ps receiver function and Rayleigh wave group velocity dispersion curve for the station (AIS : Nouvelle Amsterdam - TAAF, France) suggest Moho depth of ~14 km beneath the Amsterdam island and is well in agreement with the gravity-magnetic studies. The result clearly indicates that ASP island complex is highly affected by the ASP plume activity and was evolved during the ridge-plume interaction.</p>

Inversion of Rg waveforms recorded in southern Spain

1997 ◽  
Vol 87 (4) ◽  
pp. 847-865
Author(s):  
Manuel Navarro ◽  
Victor Corchete ◽  
José Badal ◽  
José A. Canas ◽  
Luis Pujades ◽  
...  
Keyword(s):  
Group Velocity ◽  
Velocity Structure ◽  
Group Velocity Dispersion ◽  
Shear Velocity ◽  
Dispersion Analysis ◽  
Southern Spain ◽  
Mountain Range ◽  
Low Velocity ◽  
Dispersion Data ◽  
Group Velocities

Abstract Group velocity dispersion measurements of Rg waves generated either by blasts or by local earthquakes are used to investigate the shallow crustal structure of Almería (southern Spain). In principle, the usable frequency range of 250 to 2000 mHz allows determination of structures to depths of about 4 km. For this purpose, the main operations are a detailed dispersion analysis of high-frequency Rayleigh waves propagating along very short paths and the inversion of Rg-wave group velocities. A total of 21 seismic events were studied. These events had small magnitudes (2.0 to 2.5 approximately) and very shallow focal depths (about 100 m) and were taken from a set of 214 events that occurred in 1991 during a Spanish-Italian seismic experiment. The events were recorded at seven single-component stations belonging to the Regional Seismic Network of Andalucía at approximate distances of between 15 and 57 km from the source. These events were grouped into six seismic sources according to specific criteria. We used digital filtering techniques providing a significant improvement in signal-to-noise ratio to determine ray-path group velocities, and we inverted dispersion data via generalized inversion. In order to obtain refined dispersion data, we have carried out a further regionalization of group velocities, and thus six small subregions have been resolved in group velocities. The highest group velocity values, from 1.93 to 2.25 km sec−1, correspond to the Filabres mountain range, which is an area containing materials of the Nevado-Filábride complex of Paleozoic and Triassic age. On the other hand, low velocity values, between 1.39 and 1.56 km sec−1, correspond to the Alhamilla mountain range, which belongs to the Alpujárride complex and contains conglomerates of the Cambrian and Tortonian periods. The velocities obtained for the neogene-quaternary basin of the Andarax river, with materials of the Tortonian and Pliocene periods, are also very low, between 1.35 and 1.68 km sec−1. We inverted the regionalized group velocities in order to obtain the shear velocity structure of the region for depths down to 4 km. According to the regional Earth models that we obtained, we find clear variations in velocity both laterally and vertically for several zones with different composition. The Filabres mountain range shows high shear velocity values: 2.14 to 2.83 km sec−1. In the opposite end, we have the Andarax basin that presents the lowest shear velocity values, consistent with its sedimentary structure: 1.56 to 2.55 km sec−1. Intermediate shear-wave velocities characterize the remaining regions: the Tabernas-Sorbas basin, the Gádor mountain range, and the volcanic region of Nijar-Cape of Gata. Although the relationship between lateral changes in Rg dispersion and geologic structure may not be straightforward, in this study, we have observed a correlation between those changes and the sharply contrasting geology between adjacent geological formations.

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