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Special Paper 43, Simulating tsunami inundation at Bandon, Coos County, Oregon, using hypothetical Cascadia and Alaska earthquake scenarios, by R. C. Witter, Y. Zhang, K. Wang, G. R. Priest, C. Goldfinger, L. L. Stimely, J. T. English, and P. A. Ferro.
Abstract: We develop 15 full-margin rupture models for Cascadia subduction zone earthquakes that define vertical seafloor deformation used to simulate tsunami inundation at Bandon, Oregon. Rupture models include slip partitioned to a splay fault in the accretionary wedge and models that vary the updip limit of slip on a buried megathrust fault. Coseismic slip is estimated from turbidite paleoseismic records (Goldfinger and others, 2011) and constraints from tsunami simulations at Bradley Lake (Witter and others, in press). Alternative scenarios are evaluated using a logic tree that ranks model consistency with geophysical and geological data. The hydrodynamic computer model SELFE (Zhang and Baptista, 2008) is used to simulate tsunami generation, propagation and inundation for 15 Cascadia earthquake sources and two Alaska earthquake sources: the 1964 Mw 9.2 Prince William Sound earthquake and a maximum hypothetical earthquake beneath the Gulf of Alaska. Results describe levels of confidence (in percent) that a Cascadia tsunami will not exceed simulated wave runup. Maximum Cascadia tsunami wave elevations at the shoreline vary between ~4 and ~25 m above the model tide (mean higher high water) for earthquakes with 9 to 44 m slip and moment magnitude (Mw) 8.7 to 9.2. The simulated inundation for Cascadia scenarios is consistent with the spatial extent of deposits left by the AD 1700 tsunami and older predecessors. Simulations of the 1964 tsunami agree with limited historical observations of wave heights and runup in Bandon. We recommend using the maximum Cascadia tsunami scenario and the maximum Alaska tsunami scenario for delineating evacuation zones for the Oregon coast. The most likely tsunami scenario (M1) or the large splay fault scenario (L1), which encompass ~80 to 95 percent of the hazard, should be considered for land use planning and future revisions to building codes along the coast.
SUPPLEMENTAL DATA: Two supplemental data DVDs containing GIS files and data for all 29 runs are available to purchasers of the SP-43 publication upon request to Nature of the Northwest.
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Bandon area tsunami evacuation brochure
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