The 23 January 2014 Jizan earthquake and its tectonic implications in southwestern Saudi Arabia

- Stress regime and focal mechanism solution determined for Mw 4.4 Jizan Earthquake
- Results point toward dextral strike slip fault trending in the ENE-WSW direction.
- It indicates reactivation of pre-existing faults buried in the Pre-Cambrian basement.
- Active fault is conjugate to Red Sea spreading axis and NNW-SSE Najd fault system.

A moderate-sized earthquake of Mw 4.4 occurred in southwestern Saudi Arabia on 23 January 2014. The event is considered as the largest observed earthquake that has occurred in the epicentral area. To examine the seismogenic stress regime and resolve the fault plane ambiguity, the hypocenter locations and focal mechanisms were determined using well recorded waveforms of the broadband stations operated by the Saudi Geological Survey. The current analysis included dataset consisting of mainshock and a total number of 113 well-located aftershocks. Focal mechanism solutions of the mainshock and fifteen aftershocks were determined. The focal mechanism solutions were inverted using stress tensor inversion. It indicates that the maximum compressive stress, σ1, has a nearly shallow plunge (11.8°) of ESE orientation and minimum compressive stress, σ3, has a shallow plunge (0.3°) toward NNE. Our results obtained from precise earthquake locations, focal mechanism solutions and stress tensor inversion reveal dextral strike-slip faulting over the ENE-WSW striking plane. The analysis of Coulomb failure stress emphasized the causative fault of the 2014 Jizan earthquake sequence. The active fault implies a reactivation of a high-angle fault, buried in the Precambrian basement, which is conjugate to the Red Sea spreading axis and NNW-SSE Najd fault system. The present study provided an impetus toward understanding the seismogenic stress regime in a virgin area.