Publication Date:
2015-10-23
Description:
Determining the relationship between folding and faulting in fold and thrust belts is important for understanding the growth of geological structures, the depth extent of seismic slip and consequently the potential earthquake hazard. The 2013 Mw6.2 Khaki-Shonbe earthquake occurred in the Simply Folded Belt of the Zagros Mountains, Iran. We combine seismological solutions, aftershock relocations, satellite interferometry and field observations to determine fault geometry and its relationship with the structure, stratigraphy and tectonics of the central Zagros. We image reverse slip on two along-strike, south-west dipping fault segments. The mainshock rupture initiated at the lower northern end of the larger north-west segment. Based upon the hypocentre and rupture duration, slip on the smaller southern segment is likely aseismic. Both faults verge away from the foreland, towards the high range interior, contrary to the fault geometries depicted in many structural cross-sections of the Zagros. The slip modelled occurred over two mutually exclusive depth ranges above 10km, resulting in long (∼16km), narrow rupture segments (∼7km). Aftershocks cluster in the depth range 3–14km. This indicates reverse slip and coseismic shortening occurred mostly or exclusively in the sedimentary cover, with slip distributions likely to be lithologically controlled in depth by the Hormuz salt at the base of the sedimentary cover (∼10–12km), and the Kazhdumi Formation mudrocks at upper-levels (∼4–5km). Our findings suggest lithology plays a significant role in the depth extent of slip found in reverse faults in folded belts, providing an important control on the potential size of earthquakes.
Electronic ISSN:
2333-5084
Topics:
Geosciences
,
Physics
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