The 2013 Mw 6.2 Khaki‐Shonbe (Iran) Earthquake: Insights into seismic and aseismic shortening of the Zagros sedimentary cover

• Published in: Earth and space science (Hoboken, N.J.) Vol. 2; no. 11; pp. 435 - 471
• Main Authors: Elliott, J. R., Bergman, E. A., Copley, A. C., Ghods, A. R., Nissen, E. K., Oveisi, B., Tatar, M., Walters, R. J., Yamini‐Fard, F.
• Format: Journal Article
• Language: English
• Published: 01-11-2015
• Subjects: aftershocks; earthquake; faulting; folding; insar; shortening
• ISSN: 2333-5084; 2333-5084
• DOI: 10.1002/2015EA000098

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 Mw 6.2 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 find reverse slip on two along‐strike, southwest dipping fault segments. The main shock rupture initiated at the lower northern end of the larger northwest segment. Based upon the hypocenter and rupture duration, slip on the smaller southern segment is likely aseismic. Both faults verge away from the foreland, toward the high‐range interior, contrary to the fault geometries depicted in many structural cross sections of the Zagros. The modeled slip occurred over two mutually exclusive depth ranges above 10 km, resulting in long (∼16 km), narrow rupture segments (∼7 km). Aftershocks cluster in the depth range 3–14 km. 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 (∼10–12 km), and the Kazhdumi Formation mudrocks at upper levels (∼4–5 km). 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.
Key Points
We characterize the 2013 Khaki Earthquake with seismicity and InSAR
We find significant shortening occurring only in the sedimentary cover
We find both coseismic and aseismic slip controlled in depth extent by lithology