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P-Wave Arrival-Time Tomography and Subsequent Full-Waveform Inversion of the Middle East

Session: Sensors, Seismicity and Imaging

Type: Oral

Date: 4/21/2021

Presentation Time: 05:45 PM Pacific

Description: 

The Middle Eastern region is forged by complex tectonic-driven deformations and is prone to significant seismic activity. It is vital to obtain high-resolution seismic images of such regions, using more recent and reliable datasets, in order to gain better insights of underlying geodynamics. Our study aims to retrieve a detailed model down to lithospheric depths beneath the MiddleEastern region mainly using teleseismic P arrival times from the ISC-EHB bulletin (Engdahl et al., 1998). Starting with AK135 as the reference model we invert for tomographic models of Vp perturbations in an area bounded by longitudes 22E–66E and latitudes 8N–48N. Additionally, by incorporating arrival times measured from waveforms collected at regional networks we managed to markedly improve coverage beneath the Arabian Peninsula. Our inversion results are consistent with previous regional tomographic studies. We unveil a low P velocity zone stretching from Afar to Sinai Peninsula consistent with a similar observation by Chang and van der Lee 2011. At lower smoothing levels we observe detailed structure on the Iranian Plateau similar to Simmons et al.,2011. In checkerboard tests, plus or minus 4 percent Vp perturbation amplitudes are fairly well covered for checker cells of width as low as 2.8 degrees (about 240 km at surface) beneath most of the Arabian Peninsula, Iranian Plateau, Zagros mountain region, Persian gulf, northeast Iraq, and the Anatolian-Caucasus region at depth ranges 34-135 km, 380–430 km, 650–700 km, and around 950 km.

Our ultimate goal is to perform full-waveform inversion (FWI) of the region constrained by the constructed P-wave model. We initiate our FWI with the first-generation global adjoint tomography model GLAD-M15 (Bozdag et al.,2016) which has transverse isotropy confined to the upper mantle. Our full-waveform dataset constitutes seismograms from carefully selected 100–150 events located and recorded regionally. The inversion process adopts a double-difference (Yuan et al.2016, Orsvuran et al.,2020) misfit function for the observations and synthetics.

Presenting Author: Susini Desilva

Student Presenter: No

Authors