Fault systems of the eastern Indonesian triple junction: Evaluation of Quaternary activity and implications for seismic hazards
Ian M. Watkinson, Robert Hall, 2017. "Fault systems of the eastern Indonesian triple junction: Evaluation of Quaternary activity and implications for seismic hazards", Geohazards in Indonesia: Earth Science for Disaster Risk Reduction, P. R. Cummins, I. Meilano
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Eastern Indonesia is the site of intense deformation related to convergence between Australia, Eurasia, the Pacific and the Philippine Sea Plate. Our analysis of the tectonic geomorphology, drainage patterns, exhumed faults and historical seismicity in this region has highlighted faults that have been active during the Quaternary (Pleistocene to present day), even if instrumental records suggest that some are presently inactive. Of the 27 largely onshore fault systems studied, 11 showed evidence of a maximal tectonic rate and a further five showed evidence of rapid tectonic activity. Three faults indicating a slow to minimal tectonic rate nonetheless showed indications of Quaternary activity and may simply have long interseismic periods. Although most studied fault systems are highly segmented, many are linked by narrow (<3 km) step-overs to form one or more long, quasi-continuous segment capable of producing M > 7.5 earthquakes. Sinistral shear across the soft-linked Yapen and Tarera–Aiduna faults and their continuation into the transpressive Seram fold–thrust belt represents perhaps the most active belt of deformation and hence the greatest seismic hazard in the region. However, the Palu–Koro Fault, which is long, straight and capable of generating super-shear ruptures, is considered to represent the greatest seismic risk of all the faults evaluated in this region in view of important strike-slip strands that appear to traverse the thick Quaternary basin-fill below Palu city.
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With dense urban populations located in one of the most active tectonic belts in the world, Indonesia is a hotspot for natural hazard risk. During the twentieth century, Indonesia had limited means to keep natural disaster fatalities from rising commensurately with the explosive growth in population. This situation is changing rapidly, however, with major political and economic advances over the past two decades having led to substantial investments in seismic and geodetic infrastructure. The potential for advances in Earth science to reduce natural disaster fatalities in Indonesia has never been greater.
This Special Publication documents some of the recent advances made by Earth scientists that contribute towards a better understanding of geological hazards in Indonesia.