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U.S. Geological Survey Crustal Studies Technical Letter Number 22

In cooperation with the Defense Advanced Research Projects Agency

Crustal Structure Between Lake Mead, Nevada, and Mono Lake, California

By Lane R. Johnson

1964

Thumbnail of and link to report PDF (16.2 MB)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 were used with the refraction data to calculate depths. The depth to the Moho 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 the Moho. Offsets in the Moho of 4 km at one point and 2 1/2 km at another correspond to large faults at the surface, and it is suggested that fracture zones in the upper crust may displace the Moho and extend into the upper mantle. The phase P appears to be an extension of the reflection from the top of the intermediate layer beyond the critical angle. Bouguer gravity, computed for the seismic model of the crust, is in good agreement with the measured Bouguer gravity. 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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Suggested citation:

Johnson, L.R., 1964, Crustal structure between Lake Mead, Nevada, and Mono Lake, California: U.S. Geological Survey Crustal Studies Technical Letter Number 22, 21 p. (Available at https://pubs.usgs.gov/misc/tl/0022/.)



Contents

Abstract

Introduction

Field operations

Seismic data

Mono Lake profile

Lake Mead profile

Profiles from the intermediate shot points

Seismic interpretation

Gravity data

Conclusions

Acknowledgments

References cited


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