Enhanced earthquake hazard in the Lut Block Region, Iran due to the stress evolutions since 1968

Time-dependent stress changes of the M_W≥6.3 earthquakes in the Lut Block Region following the 1968 Dasht-e Bayaz (M_W=7.1) earthquake are calculated to investigate earthquake interactions and hazards. Stress changes are computed simultaneously for all earthquakes using different Earth rheology models with varying viscosities. Results indicate that lower crustal viscosity influences viscoelastic (VE) postseismic stress changes more significantly than upper mantle viscosity. Regardless of the rheology model used, positive VE postseismic stress changes are observed at the hypocenters of the 1979 Boznabad, Korizan, and Khuli-Buniabad earthquakes, whereas negative VE postseismic stresses are computed for the 1978 Tabas-e Golshan and 2010 Rigan earthquakes. Strong VE postseismic stress loading at the 1979 Khuli-Buniabad and 1998 Fandoqa earthquake hypocenters reverses negative coseismic stresses into positive values. Conversely, at the 1981 Sirch and 2003 Bam earthquake hypocenters, positive coseismic stresses are partially offset by negative VE postseismic stresses, though not enough to produce an overall negative stress state. The Nayband, Avaz-Gazik and East Chahqanbar faults, eastern parts of the Dasht-e Bayaz and Doruneh faults, and Bam and Golbaf fault extremities are exposed to relatively strong coseismic and VE postseismic stress loads imparted by the studied earthquakes. Stress evolutions from 1968 to 2045 at the selected points indicate general stress increases, leading to estimated seismic cycle advances of 23–194 years for the southern Nayband fault (a proposed seismic gap) and 132–352 years for the eastern Doruneh fault.