A CASE-STUDY OF RUBBLE-MOUND BREAKWATERS STABILITY AGAINST MAKRAN SUBDUCTION ZONE TSUNAMIS

Abstract

A case-study pertaining to a number of existing breakwaters located on northern coastlines of the Gulf of Oman, directly facing the Makran Subduction Zone (MSZ) sets the context in order to elucidate the adopted methodologies for both Probabilistic Tsunamis Hazard Analysis (PTHA) as well as investigating breakwater stability in the event of a major tsunami. MSZ stretches from west to east for over 900 (km), affecting the coastlines of Iran, Pakistan, India, Oman and UAE as a potential source of tsunami hazard. According to historical data, the last reported MSZ generated tsunami which was triggered by the 1945CE earthquake of 8.1 (Mw) magnitude caused human fatality figures of up to almost 4,000, in addition to major structural devastation in its wake. Of particular interest, is the fate of existing breakwaters along the northern shorelines of the Gulf of Oman whose design criteria did not initially incorporate tsunami-related considerations, providing impetus for the modeling, design & analysis efforts presented in this article to serve the two-fold objective of assessing the need for strengthening existing structures, which are virtually all of the rubble-mound type, as well as deriving suitable design criteria for new breakwaters in the MSZ related tsunami affected region of Iran, earmarked for significant new developments.