Comprehensive study of the seismotectonics of the eastern Aleutian arc and associated volcanic systems. Annual progress report, March 1, 1982-February 28, 1983
This report describes completed research and related technical achievements during the first eight months, and outlines work in progress for the remaining four months of the contract period. The eastern Aleutian arc is tectonically characterized by the occurrence of very large infrequent thrust earthquakes along a subduction zone and associated volcanic arc. Within the next two decades, a great thrust event will almost certainly occur in this arc segment monitored by this study. The project is aimed to provide both a comprehensive overview of the seismicity, volcanicity, and tectonics of a major subduction zone, as well as a detailed in-depth study of its microearthquake-activity and crustal deformation. For the in-depth study we operate a digital seismic network of 14 seismic stations. The Pavlof array monitors the seismicity associated with the magmatic processes in and beneath the most active volcano of the Aleutian arc. Uniform relocation of all hypocenters for 1973-1981 show a high concentration of seismicity near the 35-km deep down-dip end of the main thrust zone, and in the overriding plate directly above the aseismic front. Teleseismic data, focal mechanisms, and tectonic evidence in the eastern and central Aleutians show a stress segmentation in the descending slab near the transition from a continental to an oceanic arc near 165/sup 0/W. Near 173/sup 0/W the Amlia fracture zone passes into the trench, tears the slab, and causes the formation of arc summit basins. Coexistence of thrust and normal faulting at depth of about 30 km beneath Kodiak and Kenai suggests strong bending moments in elastic structures of the subduction zone, structurally inherited anisotropy of fault strength, low apparent coefficients of friction for certain fault orientations, and high fluid pressures in these faults at and near the main thrust zone.
- Research Organization:
- Columbia Univ., Palisades, NY (USA). Lamont-Doherty Geological Observatory
- DOE Contract Number:
- AC02-76ER03134
- OSTI ID:
- 6642214
- Report Number(s):
- DOE/ER/03134-44; COO-3134-44; ON: DE83003010
- Resource Relation:
- Other Information: Portions of document are illegible
- Country of Publication:
- United States
- Language:
- English
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