The 1992 Flores Earthquake and the Flores Backthrust

Abstract:

The 1992 Flores earthquake (Mw=7.8) occurred on a back arc thrust near the island of Flores, Indonesia, causing widespread coastal uplift and subsidence, and generating a local tsunami with maximum runup height of over 25 meters that killed over 2,000 people. The event has been the subject of numerous publications on its various aspects, including the earthquake source mechanism determined from seismic data, and modelling of inundation and tide gauge study data to study generation of the tsunami. To date, however, no studies have quantitatively assessed the constraints placed on the source mechanism by all the different types of data - seismic, geodetic and tsunami tide gauge waveforms and inundation.

The seismic and coastal uplift data provide strong constraints on the location and orientation of the earthquake fault that are inconsistent with most published information on the “Flores Thrust”. In this talk we re-examine the constraints on the earthquake fault, and consider these in light of recent GPS and seismicity data, to suggest the existence of an active fault at depth beneath Flores Island itself.