Geology

More Slip than Meets the Eye

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Science  13 Oct 2000:
Vol. 290, Issue 5490, pp. 233
DOI: 10.1126/science.290.5490.233b

The magnitude 7.1 Hector Mine earthquake ruptured about 45 kilometers (yellow trace) of the Mojave Desert in October 1999, about seven years after the nearby magnitude 7.3 Landers earthquake. These events occurred in the eastern California shear zone, an area that accommodates about 12 millimeters per year of strike-slip motion between the Pacific and North American plates. Determining the amount and spatial distribution of deformation associated with earthquakes is necessary to understand how stresses are distributed within the plates.

Sandwell et al. obtained synthetic aperture radar interferometry (InSAR) images of the surface before and after the Hector Mine earthquake. The observations indicate about 1 to 2 meters more strike-slip offset than was mapped by geologists in the field. The additional slip probably derives from small offsets on nearby faults; their analysis also indicates triggered slip along nearby parallel faults on the west side of the main rupture, which may be a distributed zone of extension. — LR

Geophys. Res. Lett.27, 3101 (2000).

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