Title of article :
Local Tsunamis and Distributed Slip at the Source
Author/Authors :
E. L. Geist، نويسنده , , R. Dmowska ، نويسنده ,
Issue Information :
ماهنامه با شماره پیاپی سال 1999
Abstract :
Variations in the local tsunami wave fieldare examinedin relation to heterogeneous slip
distributions that are characteristic of many shallow subduction zone earthquakes. Assumptions inherent
in calculating the coseismic vertical displacement field that defines the initial condition for tsunami
propagation are examined. By comparing the seafloor displacement from uniform slip to that from an
ideal static crack, we demonstrate that dip-directed slip variations significantly affect the initial
cross-sectional wave profile. Because of the hydrodynamic stability of tsunami wave forms, these effects
directly impact estimates of maximum runup from the local tsunami. In most cases, an assumption of
uniform slip in the dip direction significantly underestimates the maximum amplitude and leading wave
steepness of the local tsunami. Whereas dip-directed slip variations affect the initial wave profile,
strike-directed slip variations result in wavefront-parallel changes in amplitude that are largely preserved
during propagation from the source region toward shore, owing to the effects of refraction. Tests of
discretizing slip distributions indicate that small fault surface elements of dimensions similar to the
source depth can acceptably approximate the vertical displacement field in comparison to continuous
slip distributions. Crack models for tsunamis generated by shallow subduction zone earthquakes indicate
that a rupture intersecting the free surface results in approximately twice the average slip. Therefore, the
observation of higher slip associatedwith tsunami earthquakes relative to typical subduction zone
earthquakes of the same magnitude suggests that tsunami earthquakes involve rupture of the seafloor,
whereas rupture of deeper subduction zone earthquakes may be imbedded and not reach the seafloor.
Keywords :
coseismic displacement , Source parameters , Tsunami , crack , tsunamirunup. , nonuniform slip
Journal title :
Pure and Applied Geophysics
Journal title :
Pure and Applied Geophysics