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1. Evacuation behaviors in tsunami drills

   https://doi.org/10.1007/s11069-022-05208-y  

   Chen, Chen ; Mostafizi, Alireza ; Wang, Haizhong ; Cox, Dan ; Cramer, Lori ( February 2022 , Natural Hazards)

   This paper presents the use of tsunami evacuation drills within a coastal community in the Cascadia Subduction Zone (CSZ) to better understand evacuation behaviors and thus to improve tsunami evacuation preparedness and resilience. Evacuees’ spatial trajectory data were collected by Global Navigation Satellite System (GNSS) embedded in mobile devices. Based on the empirical trajectory data, probability functions were employed to model people’s walking speed during the evacuation drills. An Evacuation Hiking Function (EHF) was established to depict the speed–slope relationship and to inform evacuation modeling and planning. The regression analysis showed that evacuees’ speed was significantly negatively associated with slope, time spent during evacuation, rough terrain surface, walking at night, and distance to destination. We also demonstrated the impacts of milling time on mortality rate based on participants’ empirical evacuation behaviors and a state-of-the-art CSZ tsunami inundation model. Post-drill surveys revealed the importance of the drill as an educational and assessment tool. The results of this study can be used for public education, evacuation plan assessment, and evacuation simulation models. The drill procedures, designs, and the use of technology in data collection provide evidence-driven solutions to tsunami preparedness and inspire the use of drills in other types of natural disasters such as wildfires, hurricanes, volcanoes, and flooding. 

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2. An integrative agent‐based vertical evacuation risk assessment model for near‐field tsunami hazards

   https://doi.org/10.1111/risa.13881  

   Chen, Chen ; Mostafizi, Alireza ; Wang, Haizhong ; Cox, Dan ; Chand, Cadell ( January 2022 , Risk Analysis)

   This study couples FN‐curves with Agent‐based Modeling and Simulation (ABMS) to assess risk for tsunamis with various recurrence intervals . By considering both expected number of casualties and the likelihood of tsunami events, multiple series of simulations and in‐depth analyses determine (1) how vertical evacuation structure (VES) placement impacts mortality rate; (2) what the best evacuation strategies VES locations are; and (3) where evacuees are likely to be caught by tsunami waves. The results from utilizing FN‐curves to conduct disaggregative analyses based on six tsunami scenarios indicate that choosing one tsunami scenario or averaging the risk of different scenarios may not fully articulate VES impacts due to the “levee effect,” which potentially leads to false positives. Findings show that placing VESs close to shorelines saves nearby at‐risk populations, but also results in two risk increasing phenomena: “exposure to risk” (i.e., evacuees being attracted to high risk roads by a VES when evacuating) and “blind zones” (i.e., locations near a VES where evacuees increase their risk by evacuating to that VES). When limited to one VES, placement near a population's centroid results in the lowest mortality rate. More than one VES may lower mortality rate further if VESs are spreading out according to community's topography. In addition to the analysis of tsunamis, the approach of coupling FN‐curves with ABMS can be used by local authorities and engineers to determine tailored hard‐adaptive measures and evacuation strategies, which helps to avoid maladaptive actions in different hazardous events.

    

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3. Local residents’ immediate responses to the 2018 Indonesia earthquake and tsunami

   https://doi.org/10.1177/87552930221105104  

   Wang, Haizhong ; Lindell, Michael K. ; Siam, Mohammad Rayeedul Kalam ; Chen, Chen ; Husein, Rahmawati ( July 2022 , Earthquake Spectra)

   This study analyzes 488 household residents’ responses to the 2018 Indonesia M7.5 earthquake and tsunami. Comparison of this event with past earthquake and tsunami events, such as the 2009 Samoa (M8.1), 2011 Christchurch (M6.3), and 2011 Tohoku (M9.0) events, identifies commonalities and differences among people’s responses to these events. The results show that many Palu respondents failed to recognize strong earthquake ground motion as an environmental cue to a tsunami, but this was partially offset by an informal peer warning network. Most of the warnings only mentioned one of the six recommended message elements—the tsunami hazard. However, this brief message might have been adequate for many people if they could infer the certainty, severity, and immediacy of the threat, and appropriate evacuation modes, routes, and destinations. Unlike two comparison cases, some Palu respondents actually began their evacuation later than they expected the tsunami to strike. This might be due to spending too much time milling (seeking additional information, relaying warnings, reuniting families, and preparing to evacuate)—given the tsunami’s extremely rapid onset. This finding underscores the need for coastal emergency managers to promote evacuation preparedness for near-field tsunamis in which households pack Grab and Go kits in advance, warn others while evacuating, and plan in advance where to reunite household members who must evacuate separately.

    

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4. Households’ Intended Evacuation Transportation Behavior in Response to Earthquake and Tsunami Hazard in a Cascadia Subduction Zone City

   https://doi.org/10.1177/0361198120920873  

   Chen, Chen ; Buylova, Alexandra ; Chand, Cadell ; Wang, Haizhong ; Cramer, Lori A. ; Cox, Daniel T. ( July 2020 , Transportation Research Record: Journal of the Transportation Research Board)

   null (Ed.)

   Earthquakes along the Cascadia subduction zone would generate a local tsunami that could arrive at coastlines within minutes. Few studies provide empirical evidence to understand the potential behaviors of local residents during this emergency. To fill this knowledge gap, this study examines residents’ perceptions and intended evacuation behaviors in response to an earthquake and tsunami, utilizing a survey sent to households in Seaside, OR. The results show that the majority of respondents can correctly identify whether their house is inside or outside a tsunami inundation zone. Older respondents are more likely to identify this correctly regardless of any previous disaster evacuation experience or community tenure. The majority of respondents (69%) say they would evacuate in the event of a tsunami. Factors influencing this choice include age, motor ability, access to transportation, and trust in infrastructure resiliency or traffic conditions. While the City of Seaside actively promotes evacuation by foot, 38% of respondents still state they would use a motor vehicle to evacuate. Females and older respondents are more likely to evacuate by foot. Respondents with both higher confidence in their knowledge of disaster evacuation and higher income are more likely to indicate less time needed to evacuate than others. Generally, respondents are more likely to lead rather than follow during an evacuation, especially respondents who report being more prepared for an evacuation and who have a higher perceived risk. This study showcases a unique effort at empirically analyzing human tsunami evacuation lead or follow choice behavior. 

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5. Non‐Stationary Probabilistic Tsunami Hazard Assessments Incorporating Climate‐Change‐Driven Sea Level Rise

   https://doi.org/10.1029/2021EF002007  

   Sepúlveda, Ignacio ; Haase, Jennifer S. ; Liu, Philip L. ‐F. ; Grigoriu, Mircea ; Winckler, Patricio ( June 2021 , Earth's Future)

   We face a new era in the assessment of multiple natural hazards whose statistics are becoming alarmingly non‐stationary due to ubiquitous long‐term changes in climate. One particular case is tsunami hazard affected by climate‐change‐driven sea level rise (SLR). A traditional tsunami hazard assessment approach where SLR is omitted or included as a constant sea‐level offset in a probabilistic calculation may misrepresent the impacts of climate‐change. In this paper, a general method called non‐stationary probabilistic tsunami hazard assessment (nPTHA), is developed to include the long‐term time‐varying changes in mean sea level. The nPTHA is based on a non‐stationary Poisson process model, which takes advantage of the independence of arrivals within non‐overlapping time‐intervals to specify a temporally varying hazard mean recurrence rate, affected by SLR. The nPTHA is applied to the South China Sea (SCS) for tsunamis generated by earthquakes in the Manila Subduction Zone. The method provides unique and comprehensive results for inundation hazard, combining tsunami and SLR at a specific location over a given exposure time. The results show that in the SCS, SLR has a significant impact when its amplitude is comparable to that of tsunamis with moderate probability of exceedance. The SLR and its associated uncertainty produce an impact on nPTHA results comparable to that caused by the uncertainty in the earthquake recurrence model. These findings are site‐specific and must be analyzed for different regions. The proposed methodology, however, is sufficiently general to include other non‐stationary phenomena and can be exploited for other hazards affected by SLR.

    

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