Probabilistic tsunami hazard assessment for Makran considering recently suggested larger maximum magnitudes and sensitivity analysis for GNSS-based early warning

Abstract:

Iran and Pakistan are countries frequently affected by destructive earthquakes, as for instance, the magnitude 6.6 Bam earthquake in 2003 in Iran with about 30 000 casualties, or the magnitude 7.6 Kashmir earthquake 2005 in Pakistan with about 80'000 casualties. Both events took place inland, but in terms of magnitude, even significantly larger events can be expected to happen offshore, at the Makran subduction zone. This small subduction zone is seismically rather quiescent, nevertheless a tsunami caused by a thrust event in 1945 (Balochistan earthquake) led to about 4000 casualties. Nowadays, the coastal regions are more densely populated and vulnerable to similar events. Furthermore, some recent publications discuss the possiblity of rather rare huge magnitude 9 events at the Makran subduction zone. We analyze the seismicity at the subduction plate interface and generate various synthetic earthquake catalogs spanning 100000 years. All the events are projected onto the plate interface using scaling relations and a tsunami model is run for every scenario. The tsunami hazard along the coast is computed and presented in the form of annual probability of exceedance, probabilistic tsunami height for different time periods and other measures. We show how the hazard reacts to variation of the Gutenberg-Richter parameters and maximum magnitudes.We model the historic Balochistan event and its effect in terms of coastal wave heights. Finally, we show how an effective tsunami early warning could be achieved by using an array of high-precision real-time GNSS (Global Navigation Satellite System) receivers along the coast by applying it to the 1945 event and by performing a sensitivity analysis.