Tsunami Occurrence 1900–2020: A Global Review, with Examples from Indonesia

Abstract

We present an overview of tsunami occurrences based on an analysis of a global database of tsunamis for the period 1900–2020. We evaluate the geographic and statistical distribution of various tsunami source mechanisms, high-fatality tsunamis, maximum water heights (MWHs) of tsunamis, and possible biases in the observation and recording of tsunami events. We enhance a global statistical overview with case studies from Indonesia, where tsunamis are generated from a diverse range of sources, including subduction zones, crustal faults, landslides, and volcanic islands. While 80% of global recorded tsunamis during 1900–2020 have been attributed to earthquake sources, the median MWH of earthquake tsunamis is just 0.4 m. In contrast, the median water height of landslide tsunamis is 4 m. Landslides have caused or contributed to 24% of fatal tsunamis. During 1900–2020, more tsunamis with water heights > 1 m occurred in Indonesia than in any other country. In this region fatal tsunamis are caused by subduction zone earthquakes, landslides, volcanos, and intraplate crustal earthquakes. Landslide and volcano tsunami sources, as well as coastal landforms such as narrow embayments have caused high local maximum water heights and numerous fatalities in Indonesia. Tsunami hazards are increased in this region due to the densely populated and extensive coastal zones, as well as sea level rise from polar ice melt and local subsidence. Interrelated and often extreme natural hazards in this region present both an opportunity and a need to better understand a broader range of tsunami processes.