Crustal structure between Lake Mead, Nevada, and Mono Lake, California

Abstract

Interpretation of a reversed seismic-refraction profile between Lake Mead, Nevada, and Mono Lake, California, indicates velocities of 6.15 km/sec for the upper layer of the crust, 7.10 km/sec for an intermediate layer, and 7.80 km/sec for the uppermost mantle. Phases interpreted to be reflections from the top of the intermediate layer and the Mohorovicic discontinuity (M) were used with the refraction data to calculate depths. The depth to M increases from about 30 km near Lake Mead to about 40 km near Mono Lake. Variations in arrival times provide evidence for fairly sharp flexures in M. Offsets in M of 4 km at one point and 2½ km at another correspond to large faults at the surface, and it is suggested that fracture zones in the upper crust may displace M and extend into the upper mantle. The phase urn:x-wiley:01480227:media:jgr4428:jgr4428-math-0001 appears to be an extension of the reflection from the top of the intermediate layer beyond the critical angle. Bouguer gravity anomalies, computed for the seismic model of the crust, are in good agreement with the measured Bouguer gravity anomalies. Thus a model of the crustal structure is presented which is consistent with three semi-independent sources of geophysical data: seismic refraction, seismic reflection, and gravity.

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