Articles | Volume 14, issue 11
https://doi.org/10.5194/nhess-14-3105-2014
https://doi.org/10.5194/nhess-14-3105-2014
Research article
 | 
28 Nov 2014
Research article |  | 28 Nov 2014

A probabilistic tsunami hazard assessment for Indonesia

N. Horspool, I. Pranantyo, J. Griffin, H. Latief, D. H. Natawidjaja, W. Kongko, A. Cipta, B. Bustaman, S. D. Anugrah, and H. K. Thio

Abstract. Probabilistic hazard assessments are a fundamental tool for assessing the threats posed by hazards to communities and are important for underpinning evidence-based decision-making regarding risk mitigation activities. Indonesia has been the focus of intense tsunami risk mitigation efforts following the 2004 Indian Ocean tsunami, but this has been largely concentrated on the Sunda Arc with little attention to other tsunami prone areas of the country such as eastern Indonesia. We present the first nationally consistent probabilistic tsunami hazard assessment (PTHA) for Indonesia. This assessment produces time-independent forecasts of tsunami hazards at the coast using data from tsunami generated by local, regional and distant earthquake sources. The methodology is based on the established monte carlo approach to probabilistic seismic hazard assessment (PSHA) and has been adapted to tsunami. We account for sources of epistemic and aleatory uncertainty in the analysis through the use of logic trees and sampling probability density functions. For short return periods (100 years) the highest tsunami hazard is the west coast of Sumatra, south coast of Java and the north coast of Papua. For longer return periods (500–2500 years), the tsunami hazard is highest along the Sunda Arc, reflecting the larger maximum magnitudes. The annual probability of experiencing a tsunami with a height of > 0.5 m at the coast is greater than 10% for Sumatra, Java, the Sunda islands (Bali, Lombok, Flores, Sumba) and north Papua. The annual probability of experiencing a tsunami with a height of > 3.0 m, which would cause significant inundation and fatalities, is 1–10% in Sumatra, Java, Bali, Lombok and north Papua, and 0.1–1% for north Sulawesi, Seram and Flores. The results of this national-scale hazard assessment provide evidence for disaster managers to prioritise regions for risk mitigation activities and/or more detailed hazard or risk assessment.

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Short summary
This study develops the first national probabilistic tsunami hazard assessment for Indonesia. The findings indicate that for short return periods (100 years) the south coast of Java and west coast of Sumatra have a similar hazard level to north Papua and north Sulawesi. For long return periods (2500 years) the hazard is the highest in Java and Sumatra. The results can be used to inform and prioritise tsunami risk reduction activities.
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