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.
A. H. Rajaee; M. Mokhtari; K. Priestley; D. Hatsfeld
Abstract
Using teleseismic body waves, this paper presents the crustal and lithospheric structure in the central part of the AlborzMountains for the first time. The region has been known as a very active and seismogenic locations in the past, characterized by strong earthquakes and complex structures. Tehran, ...
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Using teleseismic body waves, this paper presents the crustal and lithospheric structure in the central part of the AlborzMountains for the first time. The region has been known as a very active and seismogenic locations in the past, characterized by strong earthquakes and complex structures. Tehran, the capital of Iran, is located on the southern part of the region. The aim of this study is to determine Moho depth and its variation beneath the Central Alborz with high resolution and accuracy. The crustal structure of the Central Alborz beneath 26 broadband stations from a temporary dense seismological network was determined by using recorded data deployed for a period of 4-6 months. We first summarize an analysis of the teleseismic P-wave receiver function beneath each station. Next, we use joint inversion of receiver functions with surface wave dispersion data calculated for the center of network. Results of this research are shown as cross-sections through N-S azimuth of the profiles which passes across the AlborzMountains. Our study shows a thickening in the central part of the AlborzMountains crust down to 55 km relative to 48-50 km crustal thickness beneath northern part of the Central Iran. The crustal thickness is close to 44 km beneath the southern coast of the South Caspian Sea Block. These results are completely unlike with most of the other previous suggested crustal thickness. Based on our results, the AlborzMountains with a high average elevation can be considered with a crustal root.