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Session: Advances in Tectonic Geodesy [Poster]

Type: Poster

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

A Remote Sensing Study of the December 2017 Hojedk (Iran) Earthquake Triplet: Sequential Rupture of Conjugate Reverse Faults in a Strike-Slip Restraining Bend

A triplet of Mw ~6 earthquakes on December 1-12 2017 occurred ~50 km N of the large city of Kerman in eastern Iran. The epicenters are clustered withing a major restraining bend between the Nayband-Gowk, Lakar Kuh, and Kuh Banan fault systems, which accommodate N-directed right-lateral shear between central and eastern Iran. Here we assess the source parameters of these three events using Sentinel-1 InSAR observations and modelling, couple with pixel tracking of Planet Labs satellite photographs. All three earthquakes ruptured reverse faults probably associated with the southern termination of the Lakar Kuh right-lateral strike-slip fault. The first two large events on December 1 and December 12 (08:43 UTC) likely ruptured and reruptured a previously unrecognized, blind, NE-dipping fault beneath the Mian Kuh range. The third earthquake on December 12 (21:41 UTC) ruptured a conjugate SW-dipping thrust fault in the hanging wall of the first fault, producing a clear surface rupture in alluvial fans north of the Mian Kuh range, consistent with unusually shallow peak slip at ~0-2 km. Its high ratio of surface slip (up to ~2 m) to length (~7 km) and its narrow down-dip width implies a very high stress drop. The surface rupture aligns with a larger scarp that contains uplifted and incised fan surfaces in its hanging wall. However, this faint geomorphic expression of active faulting had not been recognized prior to these earthquakes, despite detailed structural and geomorphological studies in this area. This has wider implications for seismic hazard in mountainous parts of Iran and in restraining bends globally.

Presenting Author: Elena Savidge

Additional Authors