M.S. (Master of Science)
Department of Geology
Earthquakes--Mississippi River valley
Time variations in earthquake energy release indicate that energy from both macro- and micro-earthquakes is released cyclincally. Theoretical curves were evaluated for "best-fit" through cumulative energy release plots for the periods 1900-1925 and 1925-1978. A third-order curve was found to produce the best fit to the energy release pattern from 1900-1925, whereas an eigth-order curve, having a period of approximately 15 years, yields the best fit to the 1925-1978 energy release pattern. Projection of this latter curve into the future indicates that the embayment will experience an increase in energy release during the early 1980's. The majority of embayment earthquakes occur within the alluvial valley of the Mississippi River. The area is extensively fractured, with evidence of many major and minor faults. Duirng periods of high river stage, the increase in water mass results in anomalously high pore water pressures within the sediments beneath the river. The anomalous pressures migrate by way of the fractures to the basement rocks. Increased water pressure in the pores of a stressed rock effectively decreases the rock strength, permitting failure. Water loading, therefore, is suggested as a triggering mechanism for earthquakes occurring along the axis of the Mississippi Embayment.
Power, Kathleen M., "Time variations in energy released through earthquakes in the Mississippi embayment region" (1980). Graduate Research Theses & Dissertations. 6468.
vi, 77 pages
Northern Illinois University
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