A multi-proxy approach to assess tsunami hazard with a preliminary risk assessment: A case study of the Makran Coast, Pakistan

Abstract

Tsunamis and cyclones are sea-borne hazards capable of inundating vast coastal areas. This study aims at an extreme wave hazard assessment with a preliminary inundation analysis along the Makran Coast, Pakistan. The coastal hazard, particularly tsunamis, is evaluated by integrating five approaches: (i) probabilistic tsunami hazard assessment (PTHA); (ii) deterministic tsunami hazard assessment (DTHA); (iii) geophysical-seismic (2-D thermal modelling), (iv) sedimentary tsunami deposits (tsunamis); and (v) the historical record. The recurrence interval for a mega-tsunami event (≥12 m) is between 500 and 1000 years in the Arabian Sea. Of these mega-tsunamis, about 60% are generated by seismic sources, while the remaining 40% are attributed to secondary (co-seismic submarine landslides) and other non-seismic sources. Based on the above five approaches, the hazard analysis helped to shortlist four wave scenarios (3, 7, 10, and 15 m). Which were further used to demarcate risk areas through static inundation analysis. The results indicated that the damage potential at the coast is minor to negligible with 3 m waves and moderate with 7 m waves. Whereas the 10 m and 15 m waves will severely disrupt the study area. In addition to tsunami risk, cyclone risk is assessed by interpolating storm tracks dating back to 1842 CE. In the last 64 years, cyclone frequency has jumped from 1 cyclone per 10 years to 20 cyclones per 10 years, and the intensity has increased by two levels from Tropical Storm (TS) to Category-3.