Southwestern USA:
San Andreas plate boundary,
Cenozoic metamorphic core complexes, and Basin & Range

San Andreas - LARSE

The Los Angeles Region Seismic Experiment is a cooperative study between the Southern California Earthquake Center (funding from the National Science Foundation) and the U.S. Geological Survey. It is intended to image the crustal structure beneath the greater Los Angeles basin, and in particular, address the questions of depth to Moho, the possible existence of mid-crustal decollements, and the geometry of blind thrust faults. Also, the experiment will provide a 3-D crustal velocity structure for the region - important for improving our understanding of seismic-wave path-effects on strong ground motions accompanying large earthquakes, and for improving microearthquake hypocenter locations.

The basic experiment consisted of three wide-angle reflection - refraction onshore-offshore transects through the Los Angeles region. Field work was conducted in 1994 and 1999.

  • Langenheim, V., T.L. Wright, D. Okaya, R. Yeats, G. Fuis, and K. Thygesen, 2011, Structure of the San Fernando valley region, California: implications for seismic hazard and tectonic history, Geosphere, 7, 528-572, doi:10.1130/GES00597.1.

  • Lutter, W.J., Fuis,G.S., Ryberg,T., Okaya, D.A., Clayton, R.W., Davis, P.M., Prodehl, C., Murphy, J.M., Langenheim, V.E., Benthien, M.L., Godfrey, N.J., Christensen, N.I., Thygesen, K., Thurber, C.H., Simila, G., and Keller, G.R., 2004, Upper crustal structure from the Santa Monica Mountains to the Sierra Nevada, Southern California: tomographic results from the Los Angeles Regional Seismic Experiment, Phase II (LARSE), Bull. Seismol. Soc. Amer., 94, 619-632.

  • Fuis, G.S., Clayton, R.W., Davis, P.M., Ryberg, T., Lutter, W.J., Okaya, D.A., Hauksson, E., Prodehl., C., Murphy, J.M., Benthien, M.L., Baher, S.A., Kohler, M.D., Thygesen, K., Simila, G., and Keller, G.R., 2003, Fault systems of the 1971 San Fernando and 1994 Northridge earthquakes, southern California: Relocated aftershocks and seismic images from LARSE II, Geology, 31, 171-174.

  • Godfrey, N.J., Fuis, G.S, Langenheim, V., Okaya, D.A., and Brocher, T.M., 2002, Lower-crustal deformation beneath the central Transverse Ranges, southern California: results from the Los Angeles Region Seismic Experiment, J. Geophys. Res. 10.1029/ 2001JB000354.

  • Fuis, G.S., Ryberg, T., Godfrey, N., Okaya, D.A., and Murphy, J.M., 2001, Crustal structure and tectonics from the Los Angeles basin to the Mojave Desert, southern CA, Geology, 29, 15-18.

  • ten Brink, U.S., Zhang, J., Brocher, T.M., Okaya, D.A., Klitgord, K., and Fuis, G., 2000, The Inner California Borderlands as a possible metamorphic core complex: seismic and gravity evidence, J. Geophs. Res., 105, 5835-5857.

  • Colorado River - Core Complexes, CALCRUST & PACE

    Seismic reflection profiling in the eastern California - central Arizona region (Mojave- Sonoran deserts) indicate widespread middle crustal reflectivity. This distribution is interpreted to be related to mid-Tertiary extension which formed the metamorphic core complex belt found southwest of the Colorado Plateau.

    Colorado River - Core complexes, CALCRUST & PACE
  • Kruger, J.M., Faulds, J.E., Reynolds, S.J., and Okaya, D.A., 1998, Seismic reflection evidence for detachment polarity beneath a major accommodation zone, west-central Arizona, Geol. Soc. Am. Special Paper 323, 89-113.

  • Faulds., J.E., Schreiber, B.C., Reynolds, S.J., Gonzalez, L.A., and Okaya, D.A., 1997, Origin and paleogeography of an immense, nonmarine Miocene salt deposit in the Basin and Range (western USA), J. Geology, 105, 19-36.

  • Larkin, S., Levander, A., Okaya, D., and Goff, J., 1996, A deterministic and stochastic velocity model for the Salton Trough/Basin and Range transition zone and constraints on magmatism during rifting, J. Geophs. Res, 101, 27883-27898.

  • Malin, P., Goodman, E., Henyey, T., Li, Y.G., Okaya, D., and Saleeby, J., 1995, Significance of seismic reflections beneath a tilted exposure of deep continental crust, Tehachapi Mountains, California, J. Geophys. Res, 100, 2069-2087.

  • Flueh, E. R., and Okaya, D. A., 1989, Comparison of near-vertical and intermediate-offset (12-31 km) seismic reflection data west of the Whipple Mountain metamorphic core complex, SE California, J. Geophys. Res., 94, 625-636.

  • Goodwin, E. B., Thompson, G. A., and Okaya, D. A., 1989, Seismic identification of basement reflectors: the Bagdad reflection sequence in the Basin and Range Province - Colorado Plateau Transition zone, Arizona, Tectonics, 8, 821-831.

  • Wang, C. Y., Okaya, D., Ruppert, C., Guo, T., Davis, G. A., Zhong, Z., and Wenk, H.-R., 1989, Seismic reflectivity of the Whipple Mountain shear zone in southern California, J. Geophys. Res., 94, 2989-3005.

  • Henyey, T. E., Okaya, D. A., Frost, E. G., and McEvilly, T. V., 1987, CALCRUST (1985) seismic reflection survey, Whipple Mountains detachment terrane, California: an overview, Geophys. J. R. astr. Soc, 89, 111-118.

  • Okaya, D. A., and E. G. Frost, 1986, Application of seismic reflection profiles to structural analysis in mineral exploration, in Frontiers in geology and ore deposits of Arizona and the Southwest, Barbara Beatty and P. A. K. Wilkinson, eds., Arizona Geological Society Digest, v. XVI, 127-136.

  • Frost, E. G., and D. A. Okaya, 1986, Application of seismic reflection profiles to tectonic analysis in mineral exploration, in Frontiers in geology and ore deposits of Arizona and the Southwest, Barbara Beatty and P. A. K. Wilkinson, eds., Arizona Geological Society Digest, v. XVI, 137-152.

  • Basin & Range

  • Thompson, G. A., R. Catchings, E. Goodwin, S. Holbrook, C. Jarchow, J. McCarthy, C. Mann, and D. Okaya, 1990, Geophysics of the western Basin and Range Province, in Geophysical framework of the continental United States, L. C. Pakiser and W. D. Mooney, eds., AGU, 177-204.

  • Okaya, D. A., and G. A. Thompson, 1986, Involvement of deep crust in extension of Basin and Range province, Geol. Soc. Am. Spec. Paper 208, 15-22.

  • Okaya, D. A., 1986, Seismic profiling of the lower crust: Dixie Valley, Nevada, in AGU Geodynamics Vol. 14: Reflection Seismology: the Continental Crust, 269-280.

  • Okaya, D. A., and G. A. Thompson, 1985, Geometry of Cenozoic extensional faulting, Dixie Valley, Nevada, Tectonics, 4, 107-126.

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