The M_w 6.3 Shonbeh (Bushehr) mainshock, and its aftershock sequence: Tectonic implications and seismicity triggering

Abstract

In this study, the statistics properties of the aftershock sequence and Coulomb stress changes due to the mainshock of the  = 6.3, 9 April 2013 Shonbe earthquake have been studied. The spatial distribution of aftershocks and focal mechanism event with ≥5.0 declared a NW–SE striking rupture with oblique thrust fault mechanism. The b-value is estimated as 0.77± 0.05 and the mainshock occurred in a highly stressed region and sequence comprised larger magnitude aftershocks due to the presence of large size asperities within the rupture zone. Also the high p-value (1.16 ± 0.05), implying fast decay rate of aftershocks, evidences high surface heat flux. A value of the spatial fractal dimension ( ) equal to 2.60 ± 0.02 indicates random spatial distribution and source in a two-dimensional plane that is being filled-up by fractures. Moreover, the evaluated coseismic Coulomb stress using the variable slip model for depth range 0–20 km reveals a ‘butterfly’ pattern and most of the aftershocks fall (95%) in the region of enhanced Coulomb stress. 

Keywords

• Shonbeh Earthquake, aftershock sequence, statistics properties, Coulomb stress changes, spatial distribution

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