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Triggering of tsunamigenic aftershocks from large strike-slip earthquakes:
analysis of the November 2000 New Ireland earthquake sequence
Geochemistry Geophysics Geosystems (G3), v. 6, doi:10.1029/2005GC000935.
[Printable article (6.1 Mb)]
Geist, E. L., and T. Parsons
U.S. Geological Survey, Menlo Park, CA
Summary: It has been thought that large strike-slip earthquakes do not pose a tsunami hazard because most of the crustal motion is horizontal. Tsunamis are generated by sudden vertical sea floor offset. Thus areas like offshore California haven't been considered a likely place for local tsunamis. However, analysis of the M=8.0 2000 November New Ireland earthquake sequence shows that large strike-slip earthquakes can be indirectly responsible for lethal tsunamis. The strike-slip New Ireland earthquake transfered stress to nearby dip-slip faults (faults that mostly cause vertical deformation). These faults in turn ruptured as triggered aftershocks that caused tsunamis. Adjacent dip-slip faults are commonly associated with strike-slip faults where they bend, or step over. Thus local tsunami hazards should be considered along major offshore strike-slip fault systems.
Figure caption. Locations of hypocenters and centroids for earthquakes in 2000 New Ireland earthquake sequence (solid red). Main shock: PDE and ERI rupture trace shown. Aftershock 1: PDE and NEIC and Harvard centroid locations and mechanisms shown. Aftershock 2: NEIC centroid location and Harvard centroid location and mechanism shown. Gray region is approximate extent of rupture for the 1971 doublet (Mw = 8.0 7/14/71 and Mw = 8.1 7/26/71 earthquakes); white arrows represent approximate rupture direction as interpreted by Schwartz et al. [1989].
