STATIC EARTHQUAKE TRIGGERING AND SEISMIC HAZARD ASSESSMENT OF SULAIMAN LOBE, CENTRAL INDUS BASIN, PAKISTAN

Abstract

The purpose of this study is the seismic hazard assessment of Sulaiman lobe, Central Indus Basin, Pakistan. The curve-shaped Chaman transform fault, ~1000km long, the major active fault between Pakistan and Afghanistan demarks the western boundary of the Indian plate. Many catastrophic earthquakes have been occurred in this region. Until now, very few studies have been conducted to ascertain the earthquakes/ fault interaction and hazard assessment for this region. By employing the stress triggering theory, an earthquake sequence, comprising of fifteen earthquakes occurred in the study region since 1888 is studied. Our findings reveal that eight out of fifteen earthquakes are triggered by the preceding earthquakes. The 1908, 1910, 1935, 1966, 1997 of magnitudes Mw 6.3, 6.2, 7,4, 6.2, 7.1 respectively are somewhat independent earthquakes in this sequence. The 1935 earthquake significantly increased the positive stress at both ends of its rupture. Later, the 1975 earthquake with ΔCFS above the triggering threshold value, and the 1990 earthquake occurred on the Ghazaband fault in the southern positive lobe. Since 1935 earthquake significantly increased the ΔCFS at both ends of the rupture, the 2008 Ziarat doublet earthquakes with magnitude Mw 2008 occurred on the Urghargai fault in the northern positive stress lobe where ΔCFS is positive. Furthermore, the northern segment of Chaman fault, southern segment of the Ghazaband fault and the northwestern segment of the Urghargai fault demonstrates a high value ΔCFS. It has the potential to cause seismicity in these areas necessitating plans to prevent any future seismic hazards. The seismic hazard maps indicated that some areas needed to be studied more thoroughly due to the hazard levels expected there. This research work aims to improve our understanding of earthquake triggering and fault interaction in the area of interest. For future work, an improved CFS maps related to earthquake triggering may be produced by incorporating definite lithospheric dynamics which requires instrumental data investigations for the area being studied.