Evolution of Coulomb failure stress in Sulaiman Lobe, Pakistan, and its implications for seismic hazard assessment

In this research work, we present the evolution of Coulomb failure stress (CFS) in the Sulaiman Lobe and its implications for seismic hazard assessment. The Chaman transform fault, ~1,000 km long, is the major active fault that marks the western boundary between Pakistan and Afghanistan on the Indian Plate. To date, few studies have been conducted to unveil the interactions among earthquakes and the implications of these interactions for seismic hazard assessment in the region. We thoroughly investigated the published and online catalog to construct a sequence of major earthquakes that occurred in this region during the past. The final earthquake sequence was composed of 15 earthquakes of M_w ≥ 6.0, beginning with the 1888 earthquake. We used the stress-triggering theory to numerically simulate the evolution of CFS caused by these earthquakes. The numerical results revealed that 8 out of 15 earthquakes were triggered by the preceding earthquakes. The earthquakes in 1908, 1910, 1935, 1966, and 1997 were rather independent earthquakes in this sequence. Although the epicenters of the 1975a and 1975b earthquakes were in the stress shadow zone, the partial rupture segments of both these earthquakes were in high-CFS regions. The CFS induced by the 1935 earthquake was notable, as it later triggered the 2008 doublet. Moreover, our results revealed that the northern segment of the Chaman Fault, the southern segment of the Ghazaband Fault, and the northwestern segment of the Urghargai Fault demonstrated a high change in CFS that could trigger seismicity in these regions. The necessary arrangements must therefore be made to mitigate any possible seismic hazards in the region.