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.
J Hassanpour; S.A Alavi; S Jahani; M.R Ghassemi
Abstract
Located in the Fars region of Simply Folded Belt of the Zagros orogen, the Dadenjan salt diapir is exposed in the core, with a tendency toward the southwestern flank of the salt-cored Dadenjan anticline. The diapir is also currently situated within a transtension zone between overlapping segments of ...
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Located in the Fars region of Simply Folded Belt of the Zagros orogen, the Dadenjan salt diapir is exposed in the core, with a tendency toward the southwestern flank of the salt-cored Dadenjan anticline. The diapir is also currently situated within a transtension zone between overlapping segments of the dextral Karehbas fault zone. This diapir is sourced from the latest Precambrian-Early Cambrian Hormuz evaporitic series. The geometry of strata flanking the diapir suggests pre-orogenic, long-term salt activity by “downbuilding”, in which syn-depositional, shallow drape folding resulted in thinned and progressively rotated strata adjacent to the rising diapir. Geometrically, halokinetic sequences adjacent to this diapir are completely different on either sides of the diapir, implying different salt rise-sediment accumulation interactions. The diapir and its related anticline are bound, on both sides, by wide synclines, each with a thicker sedimentary pile than the neighboring anticlines. These synclines have acted as depocenters for the continuously rising Dadenjan diapir, accumulated significant volumes of supplied sediments, thereby facilitated the rise of salt by downbuilding mechanism. The thick sedimentary pile within these synclines has subsequently been strong enough to resist against folding and locally disturbed, to some degree, the normal stress transfer during the Zagros folding. They have therefore prevented neighboring anticlines from normal propagation and regular shape development either along or across their strikes. The Neogene Zagros folding squeezed up the salt diapir, intensified its activity and resulted in partial extrusion of the salt.
