Mohammad Tatar; M. Tatar; A. Kaviani
Abstract
Crustal structure of the Iranian plateau which is located between two convergent Arabian and Eurasian plates is studied. Teleseismic earthquakes recorded by broad band stations of Iranian National Seismic Network (INSN) are used to compute the receiver functions for each station. Rayleigh wave ...
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Crustal structure of the Iranian plateau which is located between two convergent Arabian and Eurasian plates is studied. Teleseismic earthquakes recorded by broad band stations of Iranian National Seismic Network (INSN) are used to compute the receiver functions for each station. Rayleigh wave phase velocity dispersion curves were estimated employing two-station methods for all possible station pair of the above mentioned seismic network. A combined inversion of Rayleigh wave phase velocities and body wave receiver functions increases the uniqueness of the solution over separate inversions and also facilitates explicit parameterization of layer thickness in the model space. Our result indicates the crustal thickness differs from a minimum of 40 ±2 km in southeast of Iran, (ZHSF) to a maximum of 56 ±2km beneath the Sanandaj-Sirjan zone (SNGE). We observe a crustal thickness of 47 ±2km beneath the central Zagros (GHIR) to 52 ±2km below the eastern most of Zagros (BNDS), then to 47 ±2km beneath the northwestern part of the Zagros (SHGR). Crust of the Central Iran (KRBR) has a thickness of 48 ±2 km while the average Moho depth in southern parts of the Central Alborz (DAMV and THKV stations) is 54±2km. Our analysis shows a thinning of the crust to 43 ±2 km beneath the northwest of Iran (MAKO) and western part of the Caspian basin (GRMI).
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.
F. Taghizadeh-Farahmand; F. Sodoudi; M. R. Gheitanchi; A. Kaviani
Abstract
We compute p receiver functions (RF) to investigate the crustal thickness and Vp/Vs ratio beneath the northwest of Iran and map out the lateral variation of Moho depth under this region. We selected data from teleseismic events (Mb≥5.5, 30˚>r > 95˚) recorded since 2000 to present at ...
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We compute p receiver functions (RF) to investigate the crustal thickness and Vp/Vs ratio beneath the northwest of Iran and map out the lateral variation of Moho depth under this region. We selected data from teleseismic events (Mb≥5.5, 30˚>r > 95˚) recorded since 2000 to present at 8 three component short period stations from Tabriz teleseismic network. RF method is now a well-known tool for studying crustal thickness when such a complete data set is available. As the p-to-s conversion points at the Moho is laterally close to the stations, the Moho depth estimation is less affected by lateral velocity variations and thus provides a good point measurement. First of all, we calculated RFs for each station and then the Moho depth will be estimated only from the delay time of the Moho p-to-s conversion phases. Then we used an H-Vp/Vs stacking algorithm (Zhu & Kanamori ,2000 ) to estimate crustal thickness and Vp/Vs ratio under each station from P-to-S converted waves in receiver functions. The best value for H and Vp/Vs ratio is found when the three phases (Ps and crustal multiples) are stacked coherently. The average Moho depth is approximately 48 km and varies from 38.51 to 53.51 km. Deeper and shallower Moho is found under the western and eastern stations beneath SHB and SRB stations respectively. The northwest Iran's crust has an average Vp/Vs ratio of 1.76, with higher ratio of 1.820.03 in Tabriz station and lower ratio of 1.73 0.03 in Azarshahr station.