A probabilistic tsunami hazard assessment for the Makran subduction zone at the northwestern Indian Ocean

Abstract

Due to lack of sufficient historical data of tsunami in the Makran subduction zone (MSZ) at the northwestern Indian Ocean, a probabilistic method is employed to assess the tsunami hazards in this region. The method employs a combination of probability evaluation of offshore earthquake occurrence and numerical modeling of tsunami to determine the probability of tsunami wave height exceeding a certain level. The method allowed us to determine the likelihood of tsunami in the region which is a key component of any comprehensive tsunami hazard assessment. In this study, the results of seismic hazard assessment are validated using the previous estimates of the return period of large earthquakes in the MSZ. Also, we validated our numerical modeling of tsunami using historical observations of the Makran tsunami of 1945. It has been observed that the southern coasts of Iran and Pakistan as well as Muscat are the most vulnerable areas in the region to the impact of possible tsunami. The probability of having tsunami waves exceeding 5 m during the next 50 years in these coasts is 17.5 %. In addition, a probability value as high as 45 % during the next 50 years is found for moderate tsunamis along the southern coasts of Iran and Pakistan, as well as southern coast of Oman. Based on the results, the first priority for tsunami hazard mitigation planning in the region should be given to the development of inundation maps for the southern coasts of Iran and Pakistan as well as Muscat. Also, the development of a regional tsunami warning system in the Makran zone is necessary since there is a high probability for moderate tsunami in all Makran coasts.