Stochastic analysis of tsunami runup due to heterogeneous coseismic slip and dispersion

• Published in: Journal of Geophysical Research: Oceans Vol. 117; no. C3
• Main Authors: Løvholt, F., Pedersen, G., Bazin, S., Kühn, D., Bredesen, R. E., Harbitz, C.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.03.2012; American Geophysical Union
• Subjects: dispersion; Earth sciences; Earth, ocean, space; Earthquakes; Exact sciences and technology; Geophysics; heterogeneous slip; Marine; Ocean floor; Oceanography; Physical oceanography; Plate tectonics; Seismic activity; Seismology; stochastic variation; tsunami runup; Tsunamis; Wave propagation; shorelines; near-field; dip; slopes; earthquakes; variability; linear models; Dislocation; rupture; coastal zone; Stochastic analysis; plane waves; Wave propagation; slip; standard samples; Hydrodynamic model; fault planes; deformation; tsunamis; dispersion; fault geometry; Natural hazards; Hydrostatic model; theory
• ISSN: 0148-0227; 2169-9275; 2156-2202; 2169-9291
• DOI: 10.1029/2011JC007616

Most tsunami models apply dislocation models that assume uniform slip over the entire fault plane, followed by standard analytical models based on Volterra's theory of elastic dislocations for the seabed deformation. In contrast, we quantify tsunami runup variability for an earthquake with fixed magnitude but with heterogeneous rupture distribution assuming plane wave propagation (i.e., an infinitely long rupture). A simple stochastic analysis of 500 slip realizations illustrates the expected variability in coseismic slip along a fault plane and the subsequent runup that occurs along a coastline in the near field. Because of the need for systematically analyzing different fault geometries, grid resolutions, and hydrodynamic models, several hundred thousand model runs are required. Thus, simple but efficient linear models for the tsunami generation, propagation, and runup estimation are used. The mean value and variability of the maximum runup is identified for a given coastal slope configuration and is analyzed for different dip angles. On the basis of the ensemble runs, nonhydrostatic effects are discussed with respect to their impact on generation, nearshore propagation, and runup. We conclude that for the geometry and magnitude investigated, nonhydrostatic effects reduce the variability of the runup; that is, hydrostatic models will produce an artificially high variability. Key Points Stochastic earthquake slip variation leads to variability in tsunami runup Nonhydrostatic effects such as dispersion may reduce the runup uncertainty Characteristics of the seabed displacement may reflect the tsunami potential