Tsunami Generation Efficiency of the 1994, 2006 and 2007 Kuril Islands Earthquakes

Abstract

generated trans-oceanic tsunamis that were recorded over the entire Pacific Ocean. The tsunami sources had significantly different geometries, which led to different impacts in the near-field and far-field zones. We used numerical models to investigate the source efficiency and resulting wave directivity of the three tsunamis. The tsunami models were validated and calibrated using field survey data from the Central Kuril Islands and deep-ocean bottom pressure records in the North Pacific. Using the full energy flux distribution, we conclude that the source of the 2007 event had the most well-defined energy flux directivity and that the tsunami energy radiation from the 1994 event was the most isotropic. Radiation patterns of each source clearly show the fraction of wave energy radiated into the open ocean, as well as that which penetrated into the Sea of Okhotsk through the Kuril Straits or was captured by the shelf and spread from the source area along the Kuril Ridge. We find a noticeable increase in the period of the leading wave emitted from the end of the elongated tsunami sources compared to the period of the waves formed in the transverse direction. The onshore-directed energy flux is shown to be a key factor controlling tsunami amplitudes at the coast.