Geodetic evidence for active landward tilting of the Oregon and Washington coastal ranges
Nine leveling routes that extend inland from near the coast of Oregon and Washington indicate consistent landward tilting of the 600-km-long coastal ranges at about 3 x 10/sup -8/ rad yr/sup 1/. Analysis of tide gauge observation indicates tilting with roughly the same magnitude and sense as the leveling measurements. These short-term tilt rates (10--80 yr) are comparable with longer term rates (roughly-equal100,000 yr) deduced from tilted marine terraces. Contemporary landward tiltings is interpreted to result from continuing subduction of the Juan de Fuca plate beneath North America. The similarity between long- and short-term deformation suggests that present-day subduction is occurring via aseismic creep as hypothesized by Ando and Balazs (1979). However, recent measurements of horizontal deformation in northwest Washington, which have been interpreted to indicate elastic strain accumulation, appear to be incompatible with aseismic subduction. Additional releveling observations along the Oregon routes (last observed in 1941) and further studies of late Pleistocene deformation along the coastal region of Oregon and Washington could help determine present-day tectonics and assess the risk of large thrust earthquakes in this area.
- Research Organization:
- Department of Geological Sciences, Cornell University, Ithaca, New York 14853
- OSTI ID:
- 5033000
- Journal Information:
- Geophys. Res. Lett.; (United States), Vol. 9:4
- Country of Publication:
- United States
- Language:
- English
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