Tsunami hazard assessment of Chabahar bay related to megathrust seismogenic potential of the Makran subduction zone

Abstract

Tsunami inundation mapping is the first step in the development of effective evacuation plans for communities at risk. These maps also provide bases for land use planners in communities to reduce risk by locating critical facilities out of the potential tsunami flood plain. The Makran subduction zone, located off the Indian Ocean coasts of Iran and Pakistan, is an important tsunamigenic zone for the region. On the 27th November, 1945, it was the site of a major earthquake with a moment magnitude of 8.1 and killed about 4,000 people. This event is a proof that Makran coastal areas are unsafe since the tsunami is quite probable. The objective of this study was providing tsunami inundation and hazard maps in Chabahar bay which is located in South East of Iran and the northern coast of Oman Sea. Three different source magnitude scenarios along Makran subduction zone are considered and for each scenario, numerical modeling of tsunami propagation is performed using MIKE 21 FM numerical software. Because the Makran subduction zone is very close to the Chabahar bay, unstructured triangular mesh with a higher level of refinement closer to the area of interest was used so that the tsunami was not numerically dissipated. After analyzing the data obtained from the results, inundation maps were produced, and by combining these maps, tsunami hazard map was provided for the bay. Tsunami wave amplification has been observed mainly in the outer coasts of the bay where the uplifted rocky shore experience up to 18 m wave height. Chabahar bay omega form and two eastern and western headlands cause a considerable depreciation in tsunami wave. Longer distance of coasts within the bay is another reason of tsunami depreciation inside the bay. Based on the generated inundation and hazard maps, two flood zones are specified. The first zone associated with no inundation or low inundation on cliffy shores, and the second zone would experience extensive inundation on the coast of kenarak areas, areas with sandy beaches and gentle slope.