A robust record of earthquake activity in any given region is vital to identify regions of elevated seismogenic potential, define seismogenic sources and to help forecast future rates of seismicity. Records of earthquakes predating instrumentation and those occurring while instrumentation was still in its infancy might be used to augment the relatively short duration of the instrumental era in Australia. The events occurring during these seismological eras are often termed “historical earthquakes”, and their study forms a valuable input for seismic hazard assessment. However, as with any scientific data, documentary evidence extracted from newspapers and other written materials is subject to uncertainties, incompleteness, and errors being repeated from a lack of a thorough modern re-examination of the available data. With application to seismic hazard in Australia, we revisit original sources to re-evaluate selected historical earthquakes such as the 1918 Queensland (QLD) and the 1954 Adelaide (SA) earthquakes. We discuss biases that impact the analyses of these and other historical earthquakes in Australia. Our study highlights the benefit of the critical evaluation of primary source materials to homogenise both archival and seismological materials, with modern observations, to improve our understanding of historical earthquakes in Australia. This will in turn will benefit future assessments of modern seismic hazard. Presented at the 2023 Australian Earthquake Engineering Society (AEES) National Conference

Historical reports of earthquake effects from the period 1681 to 1877 in Java, Bali and Nusa Tenggara are used to independently test ground motion predictions in Indonesia’s 2010 national probabilistic seismic hazard assessment (PSHA). Assuming that strong ground motion occurrence follows a Poisson distribution, we cannot reject Indonesia’s current PSHA for key cities in Java at 95% confidence. However, the results do suggest that seismic hazard may be underestimated for the megacity Jakarta. Ground motion simulations for individual large damaging events are used to identify plausible source mechanisms, providing insights into the major sources of earthquake hazard in the region and possible maximum magnitudes for these sources. The results demonstrate that large intraslab earthquakes have been responsible for major earthquake disasters in Java, including a ~Mw 7.5 intraslab earthquake near Jakarta in 1699 and a ~Mw 7.8 event in 1867 in Central Java. The results also highlight the potential for large earthquakes to occur on the Flores Thrust. We require an earthquake with Mw 8.4 on the Flores Thrust to reproduce tsunami observation from Sulawesi and Sumbawa in 1820. Furthermore, large shallow earthquakes (Mw > 6) have occurred in regions where active faults have not been mapped identifying the need for further research to identify and characterize these faults for future seismic hazard assessments. <b>Citation:</b> Jonathan Griffin, Ngoc Nguyen, Phil Cummins, Athanasius Cipta; Historical Earthquakes of the Eastern Sunda Arc: Source Mechanisms and Intensity‐Based Testing of Indonesia’s National Seismic Hazard Assessment. <i>Bulletin of the Seismological Society of America </i>2018; 109 (1): 43–65. doi: https://doi.org/10.1785/0120180085