Is Bali safe from a tsunami

How endangered is Bali? Tsunami simulations for Indonesia

What impact can tsunamis have in Indonesia? Which sections of the coast would be primarily affected in an emergency? How much time is there to get to safety after a tsunami warning? So far, these tsunami simulations were only accessible to the experts from the early warning centers and research institutes. The Alfred Wegener Institute (AWI) is now using the Tsunami WebGIS (web-based tsunami geographic information system) to make part of the calculations comprehensible using a clear and publicly accessible application. The AWI researchers are thus making the data products of the Sunda Trench freely available - one of the most dangerous subduction zones on earth, in which the well-known holiday island of Bali is also located.

Indonesia is the country with the greatest risk of tsunami in the world. In the past two hundred years, around two-thirds of all global tsunami deaths occurred in Indonesian territory. The Sunda Trench runs almost parallel to the coast close to the Indonesian coast, including west of the island of Sumatra. Sumatra is the island that was hardest hit by the devastating 2004 tsunami. Further south, this deep sea channel stretches along Java, one of the most densely populated islands in the world with more than 140 million inhabitants. And Bali, which is visited by more than four million tourists every year, must fear the effects of an earthquake in the subduction zone. Along the Indonesian archipelago over a length of more than 3000 km, the Indo-Australian plate is pushed under the Eurasian plate (Sundaplatte). This movement repeatedly leads to violent tremors. Movements with a vertical component are particularly dangerous. These suddenly raise large amounts of water and can lead to tsunamis.

Diverse application possible

The data contained in the new WebGIS applications correspond to the theoretically possible scenarios for the different intensities of earthquakes. The interactive map can be used in schools to show what could happen in the event of a severe seaquake off the coast of Indonesia. In the event of an earthquake, interested media can use the map to visualize or simulate the possible course of a tsunami. The card is also used to raise awareness among travelers to Indonesia so that they can behave correctly in the event of a tsunami. In addition, the knowledge platform “Earth and Environment” of the Helmholtz Association provided appropriate travel tips (Kandarr & Lauterjung, 2017).

The local public should also benefit from the simple and clear presentation. The map and instructions are therefore available in English. The Tsunami WebGIS can also be used as illustrative material for the specialist staff and employees on site in Indonesia. Employees at the Indonesian early warning center are already enthusiastic about the concept and plan to use the application for training measures.

How the interactive map for Indonesia works

In principle, the course of a subsequent tsunami can be simulated with precise location in the area shown for different seaquake strengths. Each user can choose the epicenter at the Sunda Trench and the magnitude of the quake (7.2–9.0; depending on the potential epicenter). The simulation then shows where a tsunami wave will arrive and after what time. This is used to calculate the time corridor that people remain on site to get to safety. Based on the color gradation, the potentially possible wave height can be easily identified. Even laypeople quickly realize that every earthquake has its own characteristics. The map makes local features clear. Does an offshore island protect the mainland or does it increase the risk from overlapping waves? How strong are the water masses in a bay? All of these calculations take place in the background. The integration of further simulations is planned, in which historical tsunamis are also to be recorded in the system. This also makes it possible to look back into the past, when Indonesia was repeatedly hit by severe floods caused by seaquakes.

Part of the simulations are theoretical epicentres and possible magnitudes in the Sunda Trench off Indonesia. The database on which the application is based was created as part of a large German-Indonesian cooperation project to set up an Indonesian tsunami early warning system (GITEWS: German-Indonesian Tsunami Early Warning System) and the follow-up project PROTECTS. The tsunami modeling group of the AWI had set up a database with around 4500 tsunami simulations for the Indonesian tsunami early warning system (InaTEWS), which were calculated with the tsunami model TsunAWI. Further simulations for northeast Indonesia were funded by the Australian government until 2017 and implemented together with colleagues from BMKG. As a result, 15 trenches can now be covered with over 17,000 simulations.

Detailed information on how scientists model tsunamis can be found in our ESKP article “Propagation of Tsunami Waves” (Rakowsky, 2015). As part of ESKP, part of the simulation data has now been transferred to an interactive GIS application, the Tsunami-WebGIS, on the maps @ AWI platform provided by the AWI. In general, the maps @ AWI platform offers the opportunity to present scientific geo-referenced data to a broad public. This on a wide variety of topics such as permafrost, marine mammals, garbage or the sea floor. The special Tsunami WebGIS application that is now available can be accessed here. For the first time, non-specialists and non-scientists can also gain an insight into tsunami modeling at the AWI and assess the effects of a seaquake off Indonesia.

  Alfred Wegener Institute Helmholtz Center for Polar and Marine Research. (2013-2020). TsunAWI Simulations in the Indonesia Tsunami Early Warning System [web-based tsunami geographic information system, maps.awi.de]. Accessed on 02.09.2020.

  Kandarr, J. & Lauterjung, J. (2017, July 04). “Tempat Evakuasi Sementara” saves lives in the tsunami. Earth System Knowledge Platform [eskp.de], 4. Accessed on March 8, 2018.

  Lauterjung, J. (2018). Tsunami early warning system for the most populous island in the world [interview]. ESKP topic special Metropolises under pressure. This is how cities become more sustainable [themenspezial.eskp.de]. Accessed on June 12, 2018.

  Rakowsky, N. (2015, February 16). Spread of tsunami waves. Earth System Knowledge Platform [eskp.de], 2. Accessed on March 8, 2018.

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