Federal Emergency Management Agency (FEMA) Federal Insurance Rate Map (FIRM) guidelines do not currently exist for conducting and incorporating tsunami hazard assessments that reflect the substantial advances in tsunami research achieved in the last two decades (Tsunami Pilot Study Working Group, 2006). Therefore, as part of FEMAs Modernization Program, a Tsunami Pilot Study was carried out in the Seaside/Gearhart, Oregon, area to provide information from which tsunami mapping guidelines could be developed. This area was chosen because it is typical of coastal communities in the section of the Pacific Coast from Cape Mendocino to the Strait of Juan de Fuca. There was also considerable interest shown by state agencies and local stakeholders in mapping the tsunami threat to this area. The study was an interagency effort by scientists from the U.S. Geological Survey, the National Oceanic and Atmospheric Administration, the University of Southern California, and the Middle East Technical University. We present the GIS data from that report in this publication.
These data are intended for science researchers, students, policy makers, and the general public. The data can be used with geographic information systems (GIS) software to display geologic and oceanographic information.
exrate010.shp, exrate002.shp - PTHA wave heights determined by input from all far- and near-field sources
exrate002c.shp - smoothed version of exrate002.shp
exrate010aa.shp, exrate002aa.shp - wave heights determined using only source 1 of the Alaska-Aleutian segmentation
exrate010td480.shp, exrate002td480.shp - PTHA wave heights determined using a mean inter-event time of 480 years (mean value from records)
exrate010td560.shp, exrate002td560.shp - PTHA wave heights determined using a mean inter-event time of 560 years (value from model)
Although the 100-year probabilistic inundation (exrate010) looks similar to inundation from the historic 1964 event, the 100-year probabilistic map is the aggregate of many different tsunami sources around the Pacific. From the little data available, the mean inter-event time for a 1964-type earthquake in Alaska is quite long (~750 years), although again, earthquakes are highly aperiodic.
The 500-year probabilistic map (exrate002) is dominated by Cascadia earthquakes, but because the average inter-event time is thought to be greater than 500 years for a Cascadia M~9 earthquake, the wave heights in the 500-year probabilistic map are slightly less than for a given Cascadia scenario.
The data, digital results, GIS layers, and map products in this database have been created specifically as part of a pilot study for FEMA's modernization of Flood Insurance Rate Maps (FIRMs) project. The results of the pilot study are intended to help FEMA draft new guidelines related to tsunami flooding for Coastal Flood Hazard Analysis and Mapping for the Pacific Coast of the United States. The results are intrinsically probabilistic and designed according to FEMA flood zone specifications: annual probabilities of exceedance of 1% and 0.2%. The data, digital results, GIS layers, and map products are not intended for other uses. In particular, the 1% and 0.2% annual exceedance probability tsunami flood maps are not to be used for emergency planning, evacuation, or other insurance purposes. Please refer to the National Tsunami Hazard Mitigation Program tsunami inundation maps for use in emergency planning.
Please recognize the U.S. Geological Survey (USGS) as the source of this information.
Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data.
The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.
This information is not intended for navigational purposes.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.