NDLI: Seismicity and the State of Stress in the Dezful Embayment, Zagros Fold and Thrust Belt

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Seismicity and the State of Stress in the Dezful Embayment, Zagros Fold and Thrust Belt

Content Provider	MDPI
Author	Yaghoubi, Ali Mahbaz, Seyed Bijan Dusseault, Maurice Leonenko, Yuri
Copyright Year	2021
Description	This study focuses on determining the orientation and constraining the magnitude of present-day stresses in the Dezful Embayment in Iran’s Zagros Fold and Thrust Belt. Two datasets are used: the first includes petrophysical data from 25 wells (3 to 4 km deep), and the second contains 108 earthquake focal mechanisms, mostly occurring in blind active basement faults (5 to 20 km deep). Formal stress inversion analysis of the focal mechanisms demonstrates that there is currently a compressional stress state ( $Aφ=2.0-2.2)$ in the basement. The seismologically determined $S_{Hmax}$ direction is 37° ± 10°, nearly perpendicular to the strike of most faults in the region. However, borehole geomechanics analysis using rock strength and drilling evidence leads to the counterintuitive result that the shallow state of stress is a normal/strike-slip regime. These results are consistent with the low seismicity level in the sedimentary cover in the Dezful Embayment, and may be evidence of stress decoupling due to the existence of salt layers. The stress state situation in the field was used to identify the optimally oriented fault planes and the fault friction coefficient. This finding also aligns with the prediction Coulomb faulting theory in that the N-S strike-slip basement Kazerun Fault System has an unfavorable orientation for slip in a reverse fault regime with an average SW-NE $S_{Hmax}$ orientation. These results are useful for determining the origin of seismic activity in the basin and better assessing fault-associated seismic hazards in the area.
Starting Page	254
e-ISSN	20763263
DOI	10.3390/geosciences11060254
Journal	Geosciences
Issue Number	6
Volume Number	11
Language	English
Publisher	MDPI
Publisher Date	2021-06-12
Access Restriction	Open
Subject Keyword	Geosciences Petroleum Engineering Geochemistry and Geophysics Focal Mechanisms Fault Mechanics Seismicity Stress State Dezful Embayment Zagros Fold and Thrust Belt
Content Type	Text
Resource Type	Article

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