RAPID: Local Residents' Responses to the 2018 Indonesia Earthquake and Tsunami

Oregon State University, Corvallis OR

Investigators

Abstract

This Rapid Response Research (RAPID) project examines fundamental issues on the evacuation time estimates associated with earthquake and tsunami hazards by linking social science warning research, transportation engineering, and casualty modeling. This devastating event to Palu and the nearby cities of Donggala and Mamuju, Indonesia is of major scientific relevance to American researchers because it is similar in nature to the predicted M9.0 Cascadia Subduction Zone (CSZ) earthquake. The Palu event has uniquely important implications to the coastal communities in the CSZ. First, the 20-ft tsunami generated by a M7.5 strike-slip earthquake resembles a similar local source of tsunami generation on the Pacific Northwest (PNW) coast. Understanding people's behavioral responses to the Palu earthquake and tsunami can provide unique insights to improve the preparedness of PNW coastal communities and other coastal areas of United States. Second, the Palu event represents a "worst case scenario" (earthquake, tsunami, large inland flows of mud, and liquefaction, where soil failure swallowed 1,400 houses) in which the event happened at the same time a large number of people had congregated on a beach for a festival. It is clear that the densely populated coastal areas took heavy damage because of tsunami-generated large inland flows of mud. Intense ground shaking from the preceding earthquake may have triggered soil liquefaction and lateral spreading. These combined processes are also common near streams and on reclaimed land that can produce destructive mudslides in relatively flat areas on the PNW coast from the predicted CSZ event. Third, the unique geographic location of Palu sitting at the end of a narrow 10km-long finger-like bay likely amplified the fast-moving surge of water and wave energy on the relatively shallower seabed, exacerbating the damaging power of the tsunami on the affected people and communities. There are similar communities on the PNW coast located on this type of bay. Lastly, many PNW coastal communities suffer a similar lack of tsunami preparedness. In the CSZ, the threat of near-field tsunamis has been recognized only recently, so many communities have based their evacuation plans on far-field tsunami scenarios that provide 4-6 hours of forewarning. The difficulty of predicting such events with the current technology for earthquake and tsunami warning makes it essential to learn from the Palu event. In addition, a study of Palu tsunami evacuations will inform evacuation planning for other similar type rapid-onset disasters such as flash floods. This project uses the Protective Action Decision Model (PADM) as a guide to collecting empirical data on people's behavioral responses to the Palu earthquake and tsunami. Questions include: How many people recognized the earthquake shaking as an environmental cue for a tsunami onset? How many people received warnings from officials, news media, and peers? How did people respond to the threat? This project uses a validated survey procedure previously used in American Samoa (2009), Christchurch (2011), Tohoku (2011), Cook Strait (2013), and Lake Grassmere (2013). Collected data focus on (1) the amount of time it took officials to decide to issue tsunami evacuation warnings; (2) the tsunami warning sources, channels, messages and warning dissemination times; (3) people's evacuation participation rates, preparation times, and departure times; and (4) people's evacuation logistics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.