Evaluation of tsunami potential based on conditional probability for specific zones of the Pacific tsunamigenic rim

Abstract

The Pacific tsunamigenic rim is one of the most tsunamigenic regions of the world which has experienced large catastrophic tsunamis in the past, resulting in huge loss of lives and properties. In this study, probabilities of occurrences of large tsunamis with tsunami intensity (Soloviev–Imamura intensity scale) I≥1.5, I≥2.0, I≥2.5, I≥3.0, I≥3.5 and I≥4.0 have been calculated over the next 100years in ten main tsunamigenic zones of the Pacific rim area using a homogeneous and complete tsunami catalogue covering the time periods from 684 to 2011. In order to evaluate tsunami potential, we applied the conditional probability method in each zone by considering the inter-occurrence times between the successive tsunamis generated in the past that follow the lognormal distribution. Thus, we assessed the probability of the next generation of large tsunamis in each zone by considering the time of the last tsunami occurrence. The a-posteriori occurrence of the last large tsunami has been also assessed, assuming that the time of the last occurrence coincides with the time of the event prior to the last one. The estimated a-posteriori probabilities exhibit satisfactory results in most of the zones, revealing a promising technique and confirming the reliability of the tsunami data used. Furthermore, the tsunami potential in different tsunamigenic zones is also expressed in terms of spatial maps of conditional probabilities for two levels of tsunami intensities I≥1.5 and I≥2.5 during next 10, 20, 50 and 100years. Estimated results reveal that the conditional probabilities in the South America and Alaska–Aleutian zones for larger tsunami intensity I≥2.5 are in the range of 92–93%, much larger than the Japan (69%), for a time period of 100years, suggesting that those are the most vulnerable tsunamigenic zones. The spatial maps provide brief atlas of tsunami potential in the Pacific rim area.