Geometries of Deep Crustal Faults: Evidence from the COCORP Mojave Survey

  1. Muawia Barazangi and
  2. Larry Brown
  1. M. J. Cheadle,
  2. B. L. Czuchra,
  3. C. J. Ando,
  4. T. Byrne,
  5. L. D. Brown,
  6. J. E. Oliver and
  7. S. Kaufman

Published Online: 15 MAR 2013

DOI: 10.1029/GD014p0305

Reflection Seismology: The Continental Crust

Reflection Seismology: The Continental Crust

How to Cite

Cheadle, M. J., Czuchra, B. L., Ando, C. J., Byrne, T., Brown, L. D., Oliver, J. E. and Kaufman, S. (1986) Geometries of Deep Crustal Faults: Evidence from the COCORP Mojave Survey, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0305

Author Information

  1. Institute for the Study of the Continents and Department of Geological Sciences, Cornell University, Ithaca, NY 14853

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1986

Book Series:

  1. Geodynamics Series

ISBN Information

Print ISBN: 9780875905143

Online ISBN: 9781118670118



  • Earth—Crust—Congresses;
  • Continents—Congresses;
  • Seismic reflection method—Congresses


Several reflecting horizons imaged during deep seismic reflection profiling in the western and northern Mojave Desert are interpreted as fault zones which penetrate the deep crust of that region. The most prominent is a complex, though laterally correlatable midcrustal horizon (9–20 km) which extends over the northern area of the Mojave Survey into the Basin and Range Province and is interpreted to be a major southwesterly dipping crustal fault zone. Its shape resembles ramp and flat geometry, which suggests that deep “faults” in crystalline terranes can have geometries similar to thrusts mapped in foreland thrust belts.

The crust-mantle transition appears to be represented by a continuous series of reflections which occur at about 10 s (33 km) in the north of the survey, and at about 8–9 s (26–29 km) in the south. The change in two-way travel time to this horizon, the base of which is interpreted to be the Moho, provides evidence for a fault which offsets the Moho.

The COCORP survey also traversed the two major strike-slip faults that bound the Mojave block. The San Andreas fault zone, though poorly constrained by the seismic data, appears to be a major vertical feature separating Mojave basement, with numerous discontinuous reflections down to 30 km depth, from basement to the south, which is devoid of such reflections. Conversely the Garlock fault appears to be a relatively shallow feature, extending to less than 9 km depth, because it does not offset an underlying reflecting horizon.