Population vulnerability from tsunamis is a function of the number and location of individuals in hazard zones and their ability to reach safety before wave arrival. Previous tsunami disasters can provide insight on likely evacuation behavior, but post-disaster assessments have not been used extensively in evacuation modeling. We demonstrate the utility of postdisaster assessments in pedestrian evacuation modeling for tsunami hazards and use the US territory of American Samoa as our case study. We model pedestrian travel times out of tsunami inundation zones recreated for the 2009 M w 8.1 Samoa earthquake, as well as for a probable maximum tsunami zone for future threats. Modeling assumptions are guided by fatality trends and observations of 2009 evacuation behavior, including insights on departure delays, environmental cues, transportation mode, and demographic characteristics. Differences in actual fatalities from the 2009 disaster and modeled population vulnerability suggest that a single set of estimated travel times to safety does not fully characterize evacuation potential of a dispersed, at-risk population. Efforts to prepare coastal communities in American Samoa for future tsunamis may be challenging given substantial differences in wave characteristics and evacuation potential of the probable maximum hazard compared to the 2009 event.

For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit

River valleys in the Cibao Valley Basin, located in the northern Dominican Republic, expose three fossiliferous Neogene-aged strata (the Cercado, Gurabo, and Mao formations) that show evidence for shifting marine paleo-habitats. This study system is ideal for analyzing the relationships between environmental changes and faunal community stability through time. A new database was developed from the published literature to examine changing diversity patterns and to determine if the Cibao Valley communities exhibited stasis over a 3 My time span (6.5 Ma to 3.5 Ma) across shallowto very deep-water environments. This database includes spatio-temporal occurrence data for 179 species of gastropods, bivalves, and corals. Analyses of diversity patterns reveal a high diversity of species in shallow-to deep-water depths, and a low diversity of species in very deep-water depths, as well as a low similarity of species through time across the different paleoenvironmental settings. An R-mode hierarchical cluster analysis illustrates two major clusters that were based mostly on the different paleoenvironments in which these species lived, while a Q-mode cluster analysis shows two major clusters, one consisting mostly of mollusk and the other of corals. Finally, a detrended correspondence analysis indicates higher species richness in intermediate-water depths and lower species richness in very deep-water depths. In total, these results indicate faunal instability though changing habitats across time in this study system.