Crustal Deformation Release, Failure and Tilts in Alaska
Final rept. Dec 1969-Dec 1970
ALASKA UNIV FAIRBANKS GEOPHYSICAL INST
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The main purpose of the contract was to gain insight into the crustal failure mechanism and the associated source phenomenon in Alaska. This effort includes the operation of the short-period telemetry network and the three long- period borehole installations used for the measurements of crustal tilts. Through the telemetry system there is now on hand an almost complete record on the seismicity of Central Alaska, covering a total of four years, and of much higher accuracy than was hitherto available. The operation of the borehole long- period seismometer has revealed tilts associated with earthquakes as small as magnitude 3, which are consistent with the tectonic stress axis, but do not seem to conform to elastic fault dislocation models. Analysis of literature suggests that Russian observations of the VpVs ratio, diminishing by about 0.1 prior to larger earthquakes, can be explained by the decrease in VpVs ratio due to micro-fracturing observed in the laboratory and theoretical as well as experimental work on VpVs changed as a function of porosity.
- Geology, Geochemistry and Mineralogy