The 1968 Adel, Oregon, earthquake swarm

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Schaff, Schuyler C

Issue Date

1976

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Thesis

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en_US

Keywords

Seismic Activity , Oregon , Earthquake Swarms , Heterogeneous Geological Structure , Epicenters , Duration-magnitude Relationships , Tripartite Array , Mackay Theses and Dissertations Grant Collection

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Abstract

Historical seismic activity in Oregon is investigated; it is found that earthquake swarms are not atypical of seismic activity in southern Oregon. Swarms tend to occur in regions of heterogeneous geologic structure, or at low stress levels. A swarm of earthquakes occurred during May, June, and July of 1968 near Adel, Oregon; the largest of which had magnitude 5-1 on May 30. The focal mechanism of this shock indicates left-lateral oblique- slip motion on a plane that dips 80 E and strikes N E. The vertical component of motion oh this plane is reverse fault motion, which implies a change from extensional to compression stress. 169 events were selected for detailed analysis: epicenters fell within a rectangle about 15 km long (N-S) and 6 km wide; depths averaged about 9 km. A duration-magnitude relationship was established for the tripartite array; the value of b was found to be I.13.

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Thesis Number: 1090.
Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.

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University of Nevada, Reno

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http://hdl.handle.net/11714/1669

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Mackay Theses and Dissertations Grant Collection