Title

Simulated tsunami inundation for a range of Cascadia megathrust earthquake scenarios at Bandon, Oregon, USA

Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

2013

Journal

Geosphere

Volume

9

Issue

6

First Page

1783

Last Page

1803

Abstract

Characterizations of tsunami hazards along the Cascadia subduction zone hinge on uncertainties in megathrust rupture models used for simulating tsunami inundation. To explore these uncertainties, we constructed 15 megathrust earthquake scenarios using rupture models that supply the initial conditions for tsunami simulations at Bandon, Oregon. Tsunami inundation varies with the amount and distribution of fault slip assigned to rupture models, including models where slip is partitioned to a splay fault in the accretionary wedge and models that vary the updip limit of slip on a buried fault. Constraints on fault slip come from onshore and offshore paleoseismological evidence. We rank each rupture model using a logic tree that evaluates a model's consistency with geological and geophysical data. The scenarios provide inputs to a hydrodynamic model, SELFE, used to simulate tsunami generation, propagation, and inundation on unstructured grids with <5-15 m resolution in coastal areas. Tsunami simulations delineate the likelihood that Cascadia tsunamis will exceed mapped inundation lines. Maximum wave elevations at the shoreline varied from similar to 4 m to 25 m for earthquakes with 9-44 m slip and M-w 8.7-9.2. Simulated tsunami inundation agrees with sparse deposits left by the A. D. 1700 and older tsunamis. Tsunami simulations for large (22-30 m slip) and medium (14-19 m slip) splay fault scenarios encompass 80%-95% of all inundation scenarios and provide reasonable guidelines for landuse planning and coastal development. The maximum tsunami inundation simulated for the greatest splay fault scenario (3644 m slip) can help to guide development of local tsunami evacuation zones.

DOI

10.1130/GES00899.1

Keywords

Sumatra-Andaman Earthquake; Tohoku-Oki Earthquake; Southern Coastal Oregon; Radiocarbon Age Calibration; Seismic-Hazard Analysis; Cal Kyr Bp; Subduction Zone; Great Earthquakes; Splay Fault; Surface Deformation

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