Rupture characteristics of a small-sized earthquake (MW 4.2), onshore the south Red Sea, Saudi Arabia

The present study is based on the use of Empirical Green's Function (EGF) deconvolution technique to retrieve the slip distribution of the 2014 M_w 4.2 Jizan earthquake, Saudi Arabia. Two datasets of complex Source Time Functions (STFs) were retrieved using two appropriate EGF events. We inverted the STF datasets to recover the slip distribution over both nodal planes, using the Bayesian modeling followed by a linear least-squares method. The inversion was performed assuming both planes as the fault plane and examined the goodness of fit for each nodal plane. Based on a series of finite-source inversions using different rupture velocities, we resolved the rupture velocity at 2.7-2.8 km/s and the fault plane of NNW trending; paralleling the Red Sea rift. Using the estimated rupture velocities and the preferred fault plane, we imaged quite similar slip models, exhibiting two slip patches located to the updip and downdip directions from the hypocentre. The spatiotemporal slip distributions revealed a complex rupture history of such small-sized earthquake is likely to that reported for large-sized earthquakes. A seismic moment of 2.8-3.2E+15 NM and a corresponding moment magnitude of 4.2-4-3 are inferred. The stress drops obtained from the slip distribution models were 2.2-2.5 MPa; indicating a typical value that characterized the plate-boundary earthquakes.