A building exposure model for Java, Indonesia, for use in Seismic Risk Assessment

The island of Java, Indonesia, is known to have high seismic risk due to its dense population, high seismic hazard and the abundance of seismically vulnerable buildings. However, there is a limited understanding of the spatial distribution of building types and its implications for seismic risk in the island. This gap in understanding primarily stems from the absence of a robust exposure model that covers multiple building uses at an appropriate scale to inform disaster management policies. The vast size of the building portfolio in Java, coupled with the lack of data collected specifically for use in exposure modelling, means that sources of information other than direct surveys are required to develop an exposure model. This reliance on secondary sources introduces an unknown degree of uncertainty to the exposure model which may impact the assessment of seismic risk. The purpose of this study is to (a) develop a desa (village) scale exposure model for the island of Java for multiple building uses by integrating open-source and Indonesia Government datasets with current and historical Census data, (b) understand the sources of uncertainty in the model and confidence in input datasets and (c) develop a technique to account for the greatest source of uncertainty in the model, the classification of masonry residential houses. The resulting 2020 Java exposure model indicates that there are approximately 40 million buildings on the island of Java and approximately 27 million of which are vulnerable masonry residential houses. The model is a valuable tool which can be used in future seismic risk assessments, providing credible science to inform disaster management activities.