Geophysics
Mohammadreza Jamalreyhani; Abdolreza Ghods; Seyyed Khalil Mottaghi; Esmail Shabanian; Morteza Talebian; Beijing Chen
Abstract
One of the main issues in Zagros is the extent that basement and the thick sedimentary layer participate in the observed seismicity. During Nov. 2013, five magnitude ~5 Mw events hit a region in the western end of Lurestan arc of Simply Folded Belt (SFB) of Zagros. We used the Iran-China temporary network ...
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One of the main issues in Zagros is the extent that basement and the thick sedimentary layer participate in the observed seismicity. During Nov. 2013, five magnitude ~5 Mw events hit a region in the western end of Lurestan arc of Simply Folded Belt (SFB) of Zagros. We used the Iran-China temporary network and data from regional permanent networks to relocate the events using a multiple event relocation method, calculate regional moment tensor and centeriod depths for the five moderate events and estimate a velocity model for the two nearby seismic stations using joint inversion of the receiver functions and dispersion curves. Our results show a seismic cluster of about 30 km long and 15 km width. The moment tensor solutions of the five moderate events indicate an almost pure thrust mechanism. The aftershock cloud indicate a low angle east dipping fault plane (i.e., , dip in the range of 23 o -39 o ) as the causative fault plane. The calculated centeroid of the five moderate events are about 14 km and the focal depth of all events calculated by multiple event relocation are about 10-16 km. The results indicate that the thickness of sedimentary column is less than 8 km and thus showing the whole seismic cluster happened within the basement. This observation proves wrong the hypothesis of vertical separation of mainshock and aftershocks in Ssimply folded belt FB of Zagros (Nissen et al. 2011) and implies that in the Lurestan arc the sedimentary layers are deformed aseismically.
Z. Malekzadeh; M. R. Abbassi; O. Bellier; C. Authemayou; I. Shabanian
Abstract
The present study covers the area between 500E to 510, 30`E of the Zagros Fold-and-Thrust Belt. The deformation pattern of west High Zagros Belt (HZB) has been considered to reflect a complete strain partitioning due to the Arabian oblique plate convergence and Central ...
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The present study covers the area between 500E to 510, 30`E of the Zagros Fold-and-Thrust Belt. The deformation pattern of west High Zagros Belt (HZB) has been considered to reflect a complete strain partitioning due to the Arabian oblique plate convergence and Central Iran. In this context the NW-SE trending Main Recent Fault (MRF) acts as rear boundary of the belt, kinematically taking up the strike-parallel component of oblique plate motion of Arabia, whereas the High Zagros Fault (HZF) with the same fault trend as MRF accommodates the orogen-normal shortening due to this movement. Using fault-slip inversion on fault planes mostly affecting the Bakhtiary conglomerate (Plio-Pleistocene in age) along the HZB, the deviatoric stress tensor and its shape factor (R) calculated at 29 stations. The geomorphic evidences and the fault kinematics show that the major parts of the HZF are consistent with strike-slip kinematics. This implies that the HZF also accommodates some part of strike-parallel component of oblique convergence collision.
