A combined earthquake-landslide source model for the tsunami from the 27 november 1945 M_w 8.1 makran earthquake

The tsunami of 27 November 1945 from an M_w 8.1 earthquake in the Makran subduction zone is the only instrumentally recorded and deadly tsunami in the northwest Indian Ocean; offshore Iran, Pakistan, Oman, and India. Despite the fact that some source models have been proposed based on seismic or far-field tsunami data, none of them was able to reproduce one important observation: near-field runup of 10-12 m. Here, we applied numerical modeling and examined three possible secondary sources: (1) splay faulting, (2) delayed rupture of the earthquake source, and (3) submarine landslides. These secondary sources were added to the existing state-of-the-art earthquake source for this tsunami. Results of simulations revealed that only a submarine landslidewith dimensions of 15 km (length) × 15 km (width), a thickness of 600 m, a volume of ~40 km₃, and located at 63.0° E, 24.8° N is capable of reproducing the near-field tsunami observation. Such a combined earthquake-landslide source is consistent with all available observations including far-field tsunami waveforms in Karachi (Pakistan) and Mumbai (India), with near-field runup height of 10-12 m, coastal coseismic deformation data in Pasni (subsidence) and Ormara (uplift ~1-3 m), and earthquake magnitude (M 8.0-8.3).