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TitleEffects of frictional behavior and geometry of subduction fault on coseismic seafloor deformation
AuthorWang, K; He, J
SourceBulletin of the Seismological Society of America vol. 98, no. 2, 2008 p. 571-579,
Alt SeriesEarth Sciences Sector, Contribution Series 20070124
PublisherSeismological Society of America (SSA)
Mediapaper; on-line; digital
File formatpdf
Subjectsmarine geology; tectonics; tectonic setting; tectonic interpretations; subduction; subduction zones; structural features; faults; faults, slip; deformation; seafloor topography; seismicity; seismic velocities; differential uplift; oceanic crust; oceanic lithosphere; finite element method; modelling
Illustrationsgraphs; plots
AbstractThe seismogenic zone of subduction faults appears to have an updip limit, seaward of which the fault exhibits velocity-strengthening behavior. We use a two-dimensional finite element model including a frictional subduction fault to ex-plore how coseismic strengthening of the updip segment affects seafloor deformation. For a stress drop of a few MPa along the seismogenic zone, strengthening of the updip segment by a comparable amount can prevent the rupture from breaking the trench. The resultant seafloor uplift is much larger than that predicted by a model of equal seismic moment or maximum fault slip in which the seismogenic zone extends to the trench. With a curved-fault geometry, although a lower degree of coseismic strength-ening of the updip segment leads to greater slip in the shallowest part of the fault, it produces smaller seafloor uplift, contrary to a popular belief. Given the paucity of direct observations of the coseismic behavior of the updip segment, the models yield important information for understanding rupture mechanics of subduction faults and tsunami generation. We also illustrate how the results may be used to guide fault slip parameterization in analytical dislocation models.