BRIDGE OVER TROUBLED WATERS: TSUNAMI DISASTER PREVENTION IN JAVA, INDONESIA THROUGH FORECASTING, EDUCATION AND IMPLEMENTATION A

摘要

Historical accounts document 195 regional earthquakes and 111 tsunamis in the Indonesian region (Harris and Major 2016). Most of these events caused damage over a broad region, are associated with years of aftershocks, left many cities in rubble-heaps, and generated tsunamis with run-up heights > 15 meters. On average Indonesia experiences a tsunami every 4 years over the past 400 years, but the rate for the lava region is 1 every 85 years. This region accumulates strain at 2-3 times the rate of Sumatra where mega-thrust earthquakes and large tsunamis are common, but there is no evidence over the past several hundreds of years of similar events in Java. Where is the 7-8 cm/a of convergence at the Java Trench taken up? Since the earliest historical accounts at least 30 m of potential slip may be stored along the trench, which could generate a Mw=9.0 mega-thrust event. To prepare for this eventuality we explored for tsunami deposits along the 1200 km of southern Java coastline and developed tsunami models and inundation maps for at risk communities. We also used a community-based approach to engage these communities in tsunami hazards surveys, education and evacuation drills. We discovered 1) there is evidence of paleo-tsunamis along the Java coast, 2) most of the people at risk were unaware of tsunami hazards or how to respond, 3) the most effective educational methods involved music and evacuation drills based on the 20-20-20 principle: >20 seconds of shaking is a tsunami warning that you may only have 20 minutes to evacuate to 20 meters elevation.