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Open-File Report O-13-06, Ground motion, ground deformation, tsunami inundation, coseismic subsidence, and damage potential maps for the 2012 Oregon Resilience Plan for Cascadia Subduction Zone Earthquakes, by Ian P. Madin and William J. Burns
Order publication DVD, $30, from Nature of the Northwest.
—from the report:
During the 2011 Oregon Legislative Assembly the House of Representatives passed House Resolution 3, which acknowledged the threat posed to Oregon by great subduction earthquakes from the Cascadia Subduction Zone that lies off the coast of Oregon, Washington, northern California, and British Columbia. The Resolution also charged the Oregon State Seismic Safety Policy Advisory Commission (OSSPAC) with the preparation of a resilience plan for Oregon (http://www.oregon.gov/OMD/OEM/osspac/docs/Oregon_Resilience_Plan_Final.pdf) that would estimate current vulnerabilities and recommend policies to address those vulnerabilities and increase the state’s resilience to a great earthquake. OSSPAC developed a strategy that involved the use of several workgroups to look at different parts of the problem and populated these groups with volunteers from the engineering, planning, emergency management, architectural, business, and geoscience communities as well as members of the public and representatives of state and local government. The workgroups were:
The workgroups analyzed the vulnerability of their respective sectors to the chosen earthquake scenario, a magnitude 9.0 (M 9.0) great subduction earthquake off the coast of Oregon, accompanied by a large tsunami. The likelihood of this earthquake is currently estimated to be 7–12% in the next 50 years (Goldfinger and others, 2012); the magnitude is essentially the same as the 2011 Tohoku event (http://earthquake.usgs.gov/earthquakes/eqarchives/poster/2011/20110311.php). The geologic record of great subduction earthquakes in Oregon for the last 10,000 years (Goldfinger and others, 2012) suggests that this event is about average in size for the Cascadia Subduction Zone.
The Cascadia Earthquake Scenario workgroup was charged with developing a description of the likely ground motion (strength of shaking) and ground deformation (earth movements) to be expected from the scenario event, as well as maps of the likely tsunami inundation for coastal cities. Workgroup members were:
This report describes the data sources and methods used to prepare the scenario maps. The goal was to provide maps that were as detailed and accurate as possible, using published methodology, combined with the best available published and unpublished data sources as determined by the workgroup. We made no attempt to test and compare different methods or data sources, which was beyond the scope of the report. The maps initially were intended primarily for the use of the Oregon Resilience Plan (ORP) workgroups and OSSPAC. However, because the maps and data were widely distributed to workgroup participants, it was necessary to publish this documentation along with definitive digital versions of the maps. We also expect that the information will be useful to those interested in regional Cascadia ground motion and ground failure models.
The report first describes the methods used to prepare site condition maps, National Earthquake Hazards Reduction Program (NEHRP) site class (or Vs30 values), landslide susceptibility, and liquefaction susceptibility. Data sources are introduced and described at the first instance in which they are used to prepare one of the site condition maps. For example, shear wave velocity data were used to make the NEHRP site class map, and it is described before the site class map; the statewide digital geologic map was used to develop the shear wave velocity database, so it is described in the beginning of that section. The report then describes the methods combining the site condition and ground motion input data to prepare the final maps.
Digital versions of the maps and GIS data described in this report are included on the publication DVD as a digital appendix. Maps are provided in pdf format, and the GIS data are provided in an Esri® version 10.1 geodatabase: Oregon_Resilience_Plan_Ground_Motion_and_Ground_Failure_Maps.gdb. Vector data are provided as feature classes in the geodatabase and raster data as raster datasets in the geodatabase. All feature classes and raster datasets are in Oregon Lambert Projection NAD 83 International Feet (EPSG 2292), and all rasters have a cell size of 30 m (98.4 ft). The maps have been prepared using data sources that have native resolutions in the range of several kilometers to tens of meters. These maps are not appropriate for site specific investigations, and investigations using site specific data are likely to produce results that vary from what is shown on these maps.
This publication consists of a 36-page PDF report, 38 PDF-format map plates, and an Esri® v. 10.1 format geodatabase.
Geodatabase feature classes:
Plate dimensions for Plates 1 through 7: 26 x 40 inches.
Plate dimensions for Plates 8 through 13: 13 x 20 inches.
Post publication note: Tsunami modeling data (Plates 14 through 38) used in this publication have been superseded by data shown in the DOGAMI Tsunami Inundation Map (TIM) series.
Plate dimensions for Plate 14: 38 x 28 inches; Plates 15 through 38: 26 x 40 inches.