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The AAPG/Datapages Combined Publications Database

Alaska Geological Society

Abstract


Alaska Geological Society 2003 Geology Symposium, 2003
Page 13

The 2002 Denali Fault Previous HitearthquakeNext Hit: insights from geophysics - Abstract

Jeff Freymueller,1 Sigrun Hreinsdottir,2 Natalia Ratchkovski,3 Roger Hansen,4 Hilary Fletcher,5 Chris Larsen,6 Alaska Previous HitEarthquakeNext Hit Information Center staff7

The 2002 Denali fault Previous HitearthquakeNext Hit was the largest on-land strike-slip Previous HitearthquakeNext Hit in the United States since 1857. It ruptured three faults in sequence, with over 300 km total rupture length. Geophysical investigations have focused on determining the geometry of the fault(s) at depth, deriving a slip model for the Previous HitearthquakeNext Hit from geodetic displacements and seismic records, determining the pre- and post-Previous HitearthquakeNext Hit stress fields, and studying the postseismic deformation that was caused by the Previous HitearthquakeNext Hit. Aftershocks outline, in general, the extent of the rupture, but often result from failure of nearby faults. The aftershocks following this event show considerable geometric complexity. Slip models show that most of the seismic energy was released in two or three zones along the fault, with most slip occurring in the eastern part of the rupture. Geophysical slip models are in good agreement with the surface offset observations made by geologists. Previous HitEarthquakeNext Hit focal mechanisms before and after the Previous HitearthquakeNext Hit show that the regional stress field is compressional, with the maximum compressional axis located nearly normal to the Denali fault. The stress field after the Previous HitearthquakeNext Hit shows almost the same orientation. This suggests that the Denali fault is probably mechanically weak (or has very high fluid pressures within it) to allow it to slip under such a stress field. Finally, following the Previous HitearthquakeNext Hit we have observed rapid deformation persisting for months, caused by a combination of post-seismic processes including continued slip on the fault, poroelastic relaxation, and viscous relaxation of the lower crust and/or upper mantle.

Acknowledgments and Associated Footnotes

1 Jeff Freymueller: Geophysical Institute, University of Alaska, Fairbanks, AK;

2 Sigrun Hreinsdottir: Geophysical Institute, University of Alaska, Fairbanks, AK

3 Natalia Ratchkovski: Geophysical Institute, University of Alaska, Fairbanks, AK

4 Roger Hansen: Geophysical Institute, University of Alaska, Fairbanks, AK

5 Hilary Fletcher: Geophysical Institute, University of Alaska, Fairbanks, AK

6 Chris Larsen: Geophysical Institute, University of Alaska, Fairbanks, AK

7 Alaska Previous HitEarthquakeTop Information Center staff: Geophysical Institute, University of Alaska, Fairbanks, AK

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