N Afsari; F Taghizadeh-Farahmand; M.R Ghassemi
Abstract
The AlborzMountains are part of the Alpine-Himalayan orogenic belt, situated to the south of the Caspian Sea and north of the Central Iran. . The region is undergoing extensive crustal deformation and shortening between the north-central Iran and the rigid SouthCaspianBasin crust. In this study, we used ...
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The AlborzMountains are part of the Alpine-Himalayan orogenic belt, situated to the south of the Caspian Sea and north of the Central Iran. . The region is undergoing extensive crustal deformation and shortening between the north-central Iran and the rigid SouthCaspianBasin crust. In this study, we used the P-wave receiver function modeling to investigate the crustal structure beneath the eastern part of the AlborzMountains from data recorded between 2004-2010 in Sari and Semnan seismic networks of short-period seismographs, permanently deployed across the area. We observed clear conversions (Ps) from the Moho boundary, and we used them to define a model for the crust of the eastern Alborz. Our analysis indicates a thickening of the crust from ~51±2 km beneath the northern part of the eastern Alborz to ~62±2 km beneath the central part of the region, then a thinning of the crust to ~52±2 km towards south of the eastern Alborz Mountains.
N. Afsari; F. Sodoudi; M. R. Gheitanchi; A. Kaviani
Abstract
Characterization of the detailed structure of the crust and upper mantel is an important continuing goal of geophysical studies. Teleseismic body waveforms have been used to infer crust and upper mantel structure. In this study we use teleseismic receiver function method to determine the crustal thickness ...
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Characterization of the detailed structure of the crust and upper mantel is an important continuing goal of geophysical studies. Teleseismic body waveforms have been used to infer crust and upper mantel structure. In this study we use teleseismic receiver function method to determine the crustal thickness and VP/VS ratio under Kermanshah network in north-west of Zagros using teleseismic data (30°<D<95°, mb≥5.5) which have been recorded at five short-period three component stations (2003-2007). The differential travel time between the incident P wave and P to S converted wave (delay time) is used for computation of crustal thickness. Moho depth is not sensitive to crustal P velocity but there is a trade off between Moho depth and Vp/Vs ratio. The ambiguity can be reduced by incorporating the later multiple converted phases, namely, PpPs and PpSs+ PsPs. We use the method of Zhu and Kanamori (2000). This method performs a grid search through the H and Vp/Vs space and searches for the largest summed amplitudes at the predicted times of direct conversions and multiples. By stacking receiver functions from different distances and directions, effects of lateral structural variation are suppressed and an average crustal thickness is obtained. Applying this method to five short period stations in Kermanshah reveals that the Moho depth is 42 km and varies between 36 and 51.5 km. The thinnest crust was found beneath DHR, whereas the deepest crust was observed beneath VIS. We observed that Moho depth increase from west to east (from DHR to VIS) then decrease to KOM. The average VP/VS ratio as estimated is about 1.76.
