GEOPHYSICS: Triggering a Big Quake

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Science  18 Aug 2000:
Vol. 289, Issue 5482, pp. 1109d
DOI: 10.1126/science.289.5482.1109d

In 1998, a magnitude 8.1 earthquake ruptured about 178 kilometers of oceanic crust from east to west within the Antarctic Plate, off the coast of Antarctica in the Indian Ocean. This event was the largest ever recorded within an oceanic plate and the most tectonically isolated, being far from any plate boundary or seismically active region. In addition, the orientation and motion along the fault plane did not match with the generally northeast-to-southwest trending fracture zones and their related seismicity within this area of the seafloor.

Kreemer and Holt have tried to ascertain the cause of this uncommon event with models of the vertical stress field and the horizontal strain field. The strain field model indicates that the event probably is not related to diffuse deformation from the Australian-Antarctic-Pacific Plate triple junction or an unrecognized microplate within the Antarctic Plate. The stress field model reveals that deglaciation of the nearby Antarctica ice cap may have triggered this event. Three other groups publishing in the same issue have reached similar conclusions on the basis of other data. Understanding the triggering processes that led to this extremely energetic, yet isolated rupture will help to improve our understanding of more complex tectonic regions, such as southern California, where triggering of the Hector Mine earthquake by the Landers earthquake has been suggested. — LR

Acknowledgments

Geophys. Res. Lett. 27, 2297 (2000).

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