GIS-based study of tsunami risk in the Special Region of Yogyakarta (Central Java, Indonesia)

The island of Java is located above a plate boundary within the Indonesian archipelago as part of the volcanic arc resulting from the subduction of the Indo–Australian plate beneath the Eurasian plate. Due to its emplacement, it is exposed to several geohazards, including active volcanoes and earthquakes, and its secondary effects (e.g., landslides, tsunamis). Tsunamis have repeatedly hit Java; for example, the 17th of July 2006 caused by an Mw 7.8 earthquake off the coast of western Java, or the 22nd of December 2018 triggered by the collapse of the flank of Anak Krakatau during its eruption. In most cases, tsunamis have a destructive coastal impact and can cause a significant loss of lives. Therefore, it is of high importance to determine areas situated in tsunami risk zones and estimate plans for risk reduction and prevention. We present an ArcGIS-based method to calculate tsunami risk zones for the Special Region of Yogyakarta (Central Java), including the calculation of hazard zones, vulnerability zones, and the estimation of highly exposed areas. The final risk map reflects the current risk zones in the occurrence of a tsunami and should be recalculated and re-evaluated if the environmental and socio-economic conditions change. The results can be used as a base for tsunami evacuation plans and site planning.