Potential Risk of a Tsunami in Southern Java Originating from the Sunda Megathrust Earthquake

This southern segment of Java poses a major threat to the population on the South Coast of Java Island. The recent absence of major earthquakes can be an indication that a tsunamigenic (tsunami-generating) earthquake in the South Coast of Java is a potential threat. Therefore, the initiation of an effective early warning system needs to be a top priority. This is because many people who live in coastal areas at high risk of a tsunami have little time to evacuate (Widiyantoro et al., 2020).

The results of the tsunami modeling that Widyantoro, et al., (2020) carried out showed that in the worst case scenario, in which the Sunda Megathrust of the Southern Java Segment broke simultaneously, then this event could cause a tsunami off the southern coast of Java. This worst-case scenario earthquake is modeled to generate tsunami heights of up to 20.2 m and 11.7 m in West Java and East Java, respectively.

picture3-62c7b63fbb448644db323d24.png

Modeling of tsunami sources off the South Coast of Java (Widiyantoro, et al., 2020)

The maximum height of the tsunami in the entire model area for the duration of the simulation (Widiyantoro, et al., 2020)

The maximum height of the tsunami along the southern coast of Java based on the location of east-west longitude (Widiyantoro, et al., 2020)

The simulation of the Megathrust earthquake scenario for the Southern Java segment modeled by Widiyantoro, et al (2020) is the worst scenario in which 2 sub-segments of this segment break at once and cause a Megaquake or a large earthquake with a magnitude of 9.1 (Mw 9.1). The simulation shows that the average tsunami height will be around 4.5 meters across the South Coast of Java Island. However, the worst-case scenario simulation here is still a conservative model that does not take into account the potential for underwater landslides that can be a factor that strengthens a tsunami as happened in the 2018 Palu Earthquake and Tsunami Disaster.

REFERENCE

Bilek, S. L., & Lay, T. (2018). Subduction zone megathrust earthquakes. Geosphere, 14(4), 1468-1500.

1. Harris, R., & Major, J. (2017). Waves of destruction in the East Indies: the Wichmann catalogue of earthquakes and tsunami in the Indonesian region from 1538 to 1877. Geological Society, London, Special Publications, 441(1), 9-46.
2. Philibosian, B., Sieh, K., Avouac, J. P., Natawidjaja, D. H., Chiang, H. W., Wu, C. C., ... & Wang, X. (2017). Earthquake supercycles on the Mentawai segment of the Sunda megathrust in the seventeenth century and earlier. Journal of Geophysical Research: Solid Earth, 122(1), 642-676.
3. Sieh, K. (2007). The Sunda megathrust---past, present and future. Journal of Earthquake and Tsunami, 1(01), 1-19.
4. Widiyantoro, S., Gunawan, E., Muhari, A., Rawlinson, N., Mori, J., Hanifa, N. R., ... & Putra, H. E. (2020). Implications for megathrust earthquakes and tsunamis from seismic gaps south of Java Indonesia. Scientific reports, 10(1), 1-11.