Spatial distribution and source mechanism of microearthquakes in Central Nevada

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Abstract
During the summer of 1966 a small tripartite array was established at the southern extremity of the surface faulting of the Fairview Peak earthquake of 1954. Over a period of six weeks an average 31 earthquakes per day were detected. Of these approximately 400 were selected for detailed study. Site corrections were made to reduce arrival times for all elements of the array to a common base, and the properties of the array and S-P time intervals were used to determine direction of approach, apparent surface velocity across the array, and hypocentral coordinates. Foci were found to concentrate at a depth of 10 to 15 kilometers and to cluster toward the end of the surface faulting of the 1954 earthquake. The foci were also found to lie along two planar zones. The first is parallel to the fault plane solution (strike N 11° W, dip 62° E) of the Fairview Peak earthquake and terminates at the southern extremity of the surface fracture. The second begins at this point and extends to the southwest, with foci distributed about a plane striking N 50° E and dipping 50° to the southeast. The latter zone apparently marks the southern terminus of the 1954 faulting. The polarity of the first motion of P at the array indicates predominantly dip-slip motion along the faults of both zones. The character of the seismic signatures from foci occurring closely together in space and time indicates that the complexity of the signature arises chiefly from propagation effects rather than from complexity of the time history at the source.

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