West Sumatra Tectonics and Tsunami Hazard

West Sumatra Tectonics and Tsunami Hazard

The EOS Education and Outreach group has been working with provincial to local stakeholders in West Sumatra Province for the past year. We bring this simple message: A large earthquake (M 8.8) and tsunami are likely sometime in the coming decades in West Sumatra Province, though scientists cannot predict the exact day, month, or year when this may happen. The earthquake itself would damage or destroy many existing buildings and bridges; people can protect themselves by using earthquake-resistant construction techniques for new buildings and reinforcing existing buildings. The tsunami would reach the shores of the Mentawai Islands within 5-10 minutes and would reach the mainland West Sumatran coast, including Padang, within 20-30 minutes of the earthquake. The earthquake is likely to cause power and mobile phone networks to stop working, so warning messages may not reach the public. The sea water may or may not recede before the tsunami arrives, and would recede only a few minutes before the tsunami. This means that people living near the coast should evacuate to high ground immediately after feeling an earthquake that is strong or lasts longer than one minute. In most areas, there is not enough time to wait for official warnings or to see receding water or the tsunami itself.

We are not the first to bring this message to stakeholders in West Sumatra Province, yet there remain conceptions and policies that run contrary to the science. We will build upon previous outreach efforts by continuing to seek effective ways to communicate this simple message to key stakeholders and the public; the key distinctions of our approach are that our group focuses exclusively on communication and intends to do so for the long term.

The project goals are:

1. Inform policy related to earthquake and tsunami hazard

2. Include and inform earthquake and tsunami education in school curricula

3. Build stakeholder capacity: educate government officials, school heads and teachers, and NGO leaders and staff on earthquake and tsunami hazard

Our partners:

- BPBD (Disaster Management Agency), Mentawai Regency; 

- Kogami (Komunitas Siaga Tsunami, NGO) Padang ;

 - The Emergency Preparedness Programme , SurfAid (NGO) , West Sumatra.

Background:

Research by EOS and LIPI shows that the area around West Sumatra province is likely to experience a major earthquake and tsunami sometime in the coming decades.

A combination of paleoseismic and geodetic evidence indicates that a great earthquake (MW ~8.8) and its tsunami are likely in the coming decades in the northern portion of the Mentawai patch of the Sunda megathrust (Sieh et al., 2008; Chlieh et al., 2008). The potential source of this great earthquake underlies an area offshore of Padang, around the Mentawai Islands of Siberut, Sipora, and North Pagai. Strong shaking would devastate settlements across the Mentawai Islands, Padang, and surrounding areas near the West Sumatra coast; a tsunami, likely to be devastating in size, would reach the coastlines of the Mentawai Islands within 5-10 minutes and would reach Padang and neighboring areas of the West Sumatra coast within 20-30 minutes of the earthquake. 

Recent local earthquakes and tsunamis have heightened local motivation for disaster risk reduction. The 2009 Padang earthquake caused extensive building damage and more than 1000 casualties. In the Mentawai Islands, nature has been a capricious teacher: the September 2007 MW 8.4 earthquake in the southern Mentawai patch generated strong shaking but a relatively small tsunami. When the October 2010 MW 7.8 earthquake generated much less shaking, it is not surprising that many people chose not to evacuate. Yet this earthquake produced a surprisingly large tsunami with maximum run-up heights of more than 16 m (Hill et al., submitted), ultimately killing 509 people and displacing some 11,425 (Mentawai Response). After one year, many survivors are still in temporary housing and struggling to re-establish their livelihoods far from their original villages (Ramsay, 2011). People throughout the Mentawai still feel this tragedy deeply: because the cultures of these isolated villages are different from one another, they feel that not only the people but also entire cultures were washed away. Their sense of shared responsibility for preventing future tragedy motivates disaster risk reduction: now is a critical time to support their efforts.

 

The people and governments in this area face a great challenge in reducing their vulnerability to these natural hazards. We are building partnerships with local government and NGOs to facilitate two-way communication so that scientific research informs their hazard-mitigation practice, and so that their needs and expertise inform scientific research.