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Abstract:
We present a new database called Gempa Nusantara which is a collection of 7,380 macroseismic observations for 1,200 historical earthquakes in Indonesia between 1546 and 1950. Scrutinizing preserved private and official documentation from the colonial period in Indonesia, we examined the completeness of this written record based on the gradual expansion of European influence in the Indonesian Archipelago. It was collated from written materials describing the shaking felt during earthquakes in original private and official documentation from Indonesia’s colonial period. Gempa Nusantara is the largest database of uniformly assessed intensities ever assembled for Indonesia, and as such, can correct errors and fill gaps in other modern studies of historical Indonesian earthquakes, as well as palaeoseismic studies such as the coral paleo-geodetic record from Sumatra. Despite the presence of several major active faults, conclusive evidence of earthquake surface rupture during the colonial period was limited to just two events in 1909 and 1933. We also documented extreme co-seismic ground failure in Sumatra in 1936 with striking similarities to those observed on Sulawesi in 2018. From a seismic hazard perspective, we show that the frequencies of observed intensities over the duration of our database correspond well with modern seismic hazard curves for all but a few of Indonesia’s largest cities. Our work on Gempa Nusantara is an important standalone tool for the study of earthquake hazards in Indonesia.
