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.
M. Pirouz; A. Bahroudi; M.R. Ghasemi; A. Saeidi
Abstract
The study area is located in Zagros simply folded belt, south of Firuzabad city. We have considered sedimentary basin floor deformation, initial time of folding and salt structure upwelling by using isopach data. Moreover, these data can be used to indicate ...
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The study area is located in Zagros simply folded belt, south of Firuzabad city. We have considered sedimentary basin floor deformation, initial time of folding and salt structure upwelling by using isopach data. Moreover, these data can be used to indicate the expanding development. We have used NIOC isopach data for the Permian to Paleocene and Oligomiocene. If isopach data values are reversed and the 3D patterns calculated, they can show sedimentary basin floor shape. According to the 3D patterns, sedimentary basin evolution pattern, primary time of salt structures movements and basement faults movement in Firouzabad area were obtained. Mengharak basement fault with N-S trend activated with vertical displacement in the Permian and its movement changed left lateral strike slip after Triassic. In addition, extensional structures formed in the east of Mengharak fault continued to middle Cretaceous. At the same time, Neothetys was closed and the extension structures were converted to compression structures and also Mengharak fault movement changed to right lateral strike slip. Activity of salt structures (Jahani and Firuzabad) began in Permian and its activation increased during the Cretaceous in the Mengharak fault zone.