Geophysics
Abbas Gholamzadeh; Nasim Haydarpoor
Abstract
The main purpose of this paper is studying sedimentary layer in the Qeshm Island. We use aftershocks of 27 Nov. 2005 Qeshm Island (Mb=6.0), to perfume 2D tomography of Rayleigh waves. We have analyzed surface wave data for 856 aftershocks, consist 9821 waveforms. The dispersion curves are calculated ...
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The main purpose of this paper is studying sedimentary layer in the Qeshm Island. We use aftershocks of 27 Nov. 2005 Qeshm Island (Mb=6.0), to perfume 2D tomography of Rayleigh waves. We have analyzed surface wave data for 856 aftershocks, consist 9821 waveforms. The dispersion curves are calculated in the period range between 0.1 seconds and 10 seconds, which correspond to the shallow structures of uppermost crust including sedimentary layer. Surface wave tomography has also been performed to estimate the two-dimensional group velocity maps of Rayleigh waves in the region. The isolated surface wave fundamental modes by Herman and group velocities dispersion curves obtained by it, using Yanovskaya-Ditmar linear inversion method for estimation of 2D tomography maps. Based on the ray coverage, the area divided into cells with dimension 1 Km ×1 Km. in every cell and for distinct periods the velocities were calculated. The minimum dimension of distinct heterogeneities estimated as about 3 km. Low-velocity anomalies in tomography maps can be related to the accumulation of salt plugs and some soft sediment in the area. In periods up to 4 sec, which related to shallower depths, a distinct lineation observed that may relate to a fault. It seems that this fault has cut off the sediments. Into the deeper sediment, this fault disappeared which means the sediments were softer and unbreakable.
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).