RAPID: Field Reconnaissance of the 25 October 2010 Mentawai Islands Tsunami Earthquake Offshore Sumatra

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

This Grant for Rapid Response Research (RAPID) award provides travel and field support for a team of eight investigators and three to four graduate students to conduct a reconnaissance survey of the 25 October 2010 Mentawai Islands offshore Sumatra earthquake and tsunami. On 25 October 2010, a magnitude 7.7 earthquake triggered a tsunami which impacted the Mentawai Islands and parts of the coast of western Sumatra in the Indonesian archipelago. The most recent estimate of the human toll from the tsunami exceeds 450. This is the highest tsunami death toll worldwide during the past five years. The tsunami hazard along the coastline of western Sumatra and its offshore islands has been identified repeatedly after the 2004 Sumatra-Andaman, 2005 Nias, and 2007 Bengkulu earthquakes. Educational programs have been initiated and outreach lectures given on the Mentawai Islands themselves as recent as May 2010. With the October 2010 occurrence, a warning was issued within minutes by the Pacific Tsunami Warning Center (PTWC). Initial media reports and some estimates from local scientists relate run-up heights in excess of 7 meters and inundation distances up to 1 kilometer. Post disaster reconnaissance following major natural and anthropogenic events has yielded significant new insights into both the characteristics of the events as well as the performance of natural and built infrastructure subjected to these catastrophic events. The field survey be conducted over ten days and includes rental of off-road vehicles, boats, and aircraft as needed. The field activities will include collection of perishable data that will be assembled into a comprehensive multi-scale, geo-referenced data base of tsunami damage and flood zone characteristics combined with numerical model results. The field investigation will gather data to address the following research topics. First, the Mentawai earthquake falls into the category of tsunami earthquakes, which represent only about 1/10 to 1/100 of tsunamigenic earthquakes. The tsunami community lacks proper scaling functions for the tsunami run-up associated with tsunami earthquakes. Second, landslide scarps have been reported on the Mentawai Islands. The impact zone appears to be highly localized, and the offshore earthquake may have triggered superimposed tsunamis generated by landslides. The arrival times need to be determined and validated against numerical model predictions to exclude local early arrivals due to separate submarine landslide tsunamis. The distribution of inundation heights needs to be quantified to determine whether tsunamigenic submarine landsliding occurred. Third, and finally, several animations with run-up projections have been posted on the International Tsunami Information Center list-servers. Collecting high quality inundation measurements will allow the community to infer the predictive capability of different numerical models and evaluate their potential uses for inundation mapping and operational forecasts. As part of the field study, the research team will investigate why the death toll was so high from this event, given the recently installed German-Indonesian Tsunami Early Warning System (TEWS) and the role of PTWC. The field team will give education and outreach lectures and briefings at villages surveyed.