Effect of structural heterogeneity and slip distribution on coseismic vertical displacement from rupture on the Seattle Fault

Workshops in 2001 and 2002 were convened to determine critical issues in the development of tsunami inundation maps for the Puget Sound region. The Tsunami Inundation Mapping Effort (TIME) is conducted under the multi-agency National Tsunami Hazard Mitigation Program (NTHMP). The Puget Sound Tsunami/Landslide Workshop in 2001 focused on integrated tsunami research involving a wide range of research studies and tsunami hazard mitigation issues. The 2002 Puget Sound Tsunami Sources workshop (González et al., 2003) made specific recommendations for tsunami source modeling and improving our state of knowledge for sources in the Puget Sound region. One of the recommendations stated in González et al. (2003) is "Develop methods to assess the sensitivity of coastal areas to tsunami inundation, based on multiple simulations that reflect the possible range of variations in the source parameters." Tsunami inundation models rely heavily on the imposed initial conditions which, for an earthquake source, is the coseismic vertical displacement field. For example, Koshimura et al. (2002) use the geologic uplift observations (Buknam et al., 1992) to constrain the slip distribution for the event that occurred 1100 years ago, resulting in an average slip of 3.7 m and a magnitude of 7.6. Walsh et al. (2003) develop a tsunami inundation map for Elliot Bay based on a M 7.3 earthquake and the geologic uplift observations from the 1100 y.b.p. event as in Koshimura et al. (2002), though they use a constant fault dip of 60° rather than different dips for deep and shallow segments. The objective of this report is to examine how coseismic vertical displacement from a smaller M 6.5 Seattle Fault earthquake (as in Hartzell et al., 2002) is affected by structural heterogeneity and different slip distribution patterns.