H. Kianimehr; F. Yaminifard; M. Tatar; E. Kissling
Abstract
The Zagros fold and thrust belt contains a near continuous sedimentary cover which overlies the late Precambrian-Cambrian Hormuz salt formation. The information about this structure is only limited to the study of salt domes. As the density variation of salt is not noticeable with depth, it is expected ...
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The Zagros fold and thrust belt contains a near continuous sedimentary cover which overlies the late Precambrian-Cambrian Hormuz salt formation. The information about this structure is only limited to the study of salt domes. As the density variation of salt is not noticeable with depth, it is expected this structure has a significant role in the decrement of P-wave velocity relative to top layers. The 9 April, 2013 Kaki earthquake (MW 6.2), occurred in a part of the Simply Folded Belt of Zagros Mountains where there are two salt domes. So, in case of studying salt structures as low velocity zones at depth, the 1-D inversion was done using 10459 P-arrival times of 978 aftershocks. The results of this study indicate that the two top layers with overall 4km thickness and average low velocities might be related to incompetent and upper-mobile groups. Sudden seismic velocity increment from 3.9 km/s to 5.45 km/s in depth of 4 km can be considered as an indicator for transformation from the upper-mobile to the competent group. Furthermore, an average low velocity zone from 8 km to 12 km is observed that confirms the Hormuz salt series at depth.
A. Gholam Zadeh; F. Yamini-Fard
Abstract
A moderate earthquake (MW= 6.0) struck the Qeshm Island in the Hormozgan province on November 27, 2005 (17:22 GMT) and resulted in a severe damage and about 10 casualties. The main-shock was followed by an aftershock with magnitude MW=5.5 with different focal mechanisms from main-shock. A dense local ...
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A moderate earthquake (MW= 6.0) struck the Qeshm Island in the Hormozgan province on November 27, 2005 (17:22 GMT) and resulted in a severe damage and about 10 casualties. The main-shock was followed by an aftershock with magnitude MW=5.5 with different focal mechanisms from main-shock. A dense local network including 17 stations was installed in the region for aftershock study. Analysis of aftershock data shows diffuse distribution of the aftershocks; however, an alignment trending NW consistent with main shock focal mechanism is clear at depth. Two types of focal mechanisms can be observed: strike-slip and reverse. Diffused pattern of aftershock seismicity and focal mechanisms do not allow us to make a distinction between two possible explanations: occurrence of the second event in NW oriented strike-slip fault or partitioning of the deformation in the western border of the Hormoz Straight by reverse and left-lateral strike-slip faults.
F. Yamini-Fard; A. S-Moradi; M. Hosseini; R. Norouzi
Abstract
From June 2004 to December 2008 low seismic activity was recorded near North-Tehran, Taleghan and Kahrizak faults and inside of Tehran city. In contrast, seismic activity along Mosha, Garmsar and North-Alborz faults is considerable. Generally seismic activity decreases from 51 degrees longitude to west. ...
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From June 2004 to December 2008 low seismic activity was recorded near North-Tehran, Taleghan and Kahrizak faults and inside of Tehran city. In contrast, seismic activity along Mosha, Garmsar and North-Alborz faults is considerable. Generally seismic activity decreases from 51 degrees longitude to west. Two earthquakes with 15 and 17 km depth were located in the west of Tehran city. The calculated focal mechanism for one of them is pure strike-slip. High seismic activity is observed along Mosha fault close to Damavand, Boumehen cities and Lavasant-e-Bozorg region. Calculated focal mechanisms along this fault includes both strike-slip, and reverse mechanisms that implies transpression motion, dominantly left-lateral slip along this fault that continued to Lavasanat region in south of the eastern end of the North Tehran fault. Precise location of some events shows depth range of 4-32 km. Generally, calculated focal mechanisms in studied region include both strike-slip and reverse mechanisms and seems that in southern part, approaching Central Iran, reverse mechanisms are dominant. It implies slip partitioning in southern margin of Central Alborz.
