HR: 1330h
AN: S42E-0222    [PDF]
TI: A Study of the Shallow Seismicity (1971-1999) in the Anchorage, Alaska, Region
AU: * Flores, C
EM: cflores@es.ucsc.edu
AF: University of California, Santa Cruz, Department of Earth Sciences 1156 High St., E&MS, A234, Santa Cruz, CA 95064 United States
AU: Doser, D I
EM: doser@geo.utep.edu
AF: University of Texas at El Paso, Department of Geological Sciences, El Paso, TX 79968 United States
AB: Previous earthquake studies in the Anchorage region (60 to 62N, 148 to 152W) have shown little to no correlation between shallow earthquakes (depths less than 30 km) and known large-scale faults. The Double Difference earthquake relocation technique is utilized in this study to identify seismogenic structures in more detail, thus contributing information needed for future seismic hazard assessment. These hypocenter relocations indicate a number of linear, seismogenic features, some of which appear to correlate with mapped faults. The nearest concentration of crustal seismicity to the city of Anchorage is located within Upper Cook Inlet. This seismicity seems to involve deformation along several smaller en echelon structures. These structures do not appear to be associated with mapped faults and anticlines but may correlate with longer wavelength features seen in filtered aeromagnetic data. The principal orientations of stress determined from the inversion of first motion data for these events show that the regional principal stress orientation is not aligned with the regional direction of plate convergence. This principal stress orientation, however, is not uncommon for the region when compared to borehole breakout and other focal mechanism studies. The stress results are also consistent with geodetic studies that suggest that the North American plate is not strongly coupled to the down going Pacific plate within the Upper Cook Inlet/western Kenai Peninsula region.
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting