Inferences about the local stress field from focal mechanisms: Applications to earthquakes in the southern Great Basin of Nevada

Journal Article · Mon Dec 01 04:00:00 EST 1986 · Bulletin of the Seismological Society of America

OSTI ID:60179

Harmsen, S C; Rogers, A M

Focal mechanisms determined from regional-network earthquake data or aftershock field investigation often contain members ranging from strike slip to normal slip in extensional tectonic environments or from strike slip to thrust slip in compressional environments. Although the coexistence of normal and strike-slip faulting has suggested to some investigators that the maximum and intermediate principal stresses are of approximately equal magnitude, several have asserted that the directions of principle stresses can or must interchange to accommodate both types of mechanisms (Zoback and Zoback 1980b; Vetter and Ryall, 1983). A Coulomb-Navier criterion of slip is invoked to demonstrate that both types of mechanisms, as well as oblique members having preferred nodal-plane dips intermediate between those of the strike-slip and normal mechanisms, may be observed in a region where the stress field, resolved into principal components, is axially symmetric. The proximate coexistence of earthquakes having diverse focal mechanisms could be interpreted as evidence for an approximately axially symmetric stress field in a region where optimally oriented planes of weakness are known to exist in the host rock. 10 refs., 6 figs.

• OSTI ID: 60179
• Journal Information: Bulletin of the Seismological Society of America, Journal Name: Bulletin of the Seismological Society of America Journal Issue: 6 Vol. 76; ISSN 0037-1106; ISSN BSSAAP
• Country of Publication: United States
• Language: English

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