Crustal deformation across and beyond the Los Angeles basin from geodetic measurements

We combine 6 years of Global Positioning System (GPS) data with 20 years of trilateration data and a century of triangulation, taped distance, and astronomic azimuth measurements to derive 66 interseismic station velocities in the greater Los Angeles region. We interpolate the velocities to construct a regional strain rate map beyond the Los Angeles basin. Our results generally agree with the model proposed by the Working Group on California Earthquake Probabilities in 1995. Important regional findings of this study are as follows: (1) There is a significant N-S convergence and E-W extension, about 0.22 and 0.17 : 0.05 #strain/yr, respectively, for the two components, along the southern frontal fault system of the San Gabriel Mountains. (2) The crustal deformation around the Big Bend of the San Andreas fault (SAF) cannot be explained solely by wrench-style motion across the SAF. Remaining motion could be part of a NW-SE extension which is the response to NFSW compression in the central Transverse Ranges region. Alternatively, it could be caused by left-lateral faulting on an oblique blind thrust beneath the San Gabriel Mountains. (3) Low strain rates axe found along the Elsinore fault and Newport-Inglewood (4) North-south compression decreases from the Raymond Hill fault westward to the Santa Monica fault. There is little east-west extension along this fault system.

[1]  H. Kanamori,et al.  Seismic structure of the Transverse Ranges, California , 1977 .

[2]  Kurt L. Feigl,et al.  Space geodetic measurement of crustal deformation in central and southern California , 1993 .

[3]  R. Yeats,et al.  Convergence rates across a displacement transfer zone in the western Transverse Ranges, Ventura basin, California , 1995 .

[4]  D. Jackson,et al.  Aseismic crustal deformation in the Transverse Ranges of Southern California , 1987 .

[5]  D. Jackson.  The use of a priori data to resolve non‐uniqueness in linear inversion , 1979 .

[6]  P. Bird,et al.  Kinematics of present crust and mantle flow in southern California , 1984 .

[7]  J. C. Savage,et al.  Geodetic monitoring of the southern San Andreas Fault, California, 1980–1991 , 1995 .

[8]  D. Jackson,et al.  A three-dimensional viscoelastic model of a strike slip fault , 1977 .

[9]  Steven N. Ward.  A multidisciplinary approach to seismic hazard in southern California , 1994 .

[10]  F. C. Frank,et al.  Deduction of earth strains from survey data , 1966 .

[11]  R. Weldon,et al.  Deformation across the western United States: A local estimate of Pacific‐North America transform deformation , 1994 .

[12]  Richard H. Jahns,et al.  Holocene activity of the San Andreas fault at Wallace Creek , 1984 .

[13]  R. Weldon,et al.  A kinematic model of southern California , 1986 .

[14]  Duncan Carr Agnew,et al.  Application of the global positioning system to crustal deformation measurement: 1. Precision and accuracy , 1991 .

[15]  R. Clayton,et al.  Tomographic Image of the Southern California Mantle , 1990 .

[16]  H. Kanamori,et al.  Earthquake focal mechanisms in the Eastern Transverse Ranges and San Emigdio Mountains, Southern California and evidence for a regional decollement , 1985 .

[17]  Y. Bock,et al.  Global Positioning System Network analysis with phase ambiguity resolution applied to crustal deformation studies in California , 1989 .

[18]  Thomas L. Davis,et al.  A cross section of the Los Angeles Area: Seismically active fold and thrust belt, The 1987 Whittier Narrows earthquake, and earthquake hazard , 1989 .

[19]  D. Jackson,et al.  A viscoelastic relaxation model for post-seismic deformation from the San Francisco earthquake of 1906 , 1977 .

[20]  David D. Jackson,et al.  Seismic hazards in southern California: probable earthquakes, 1994 to 2024 , 1996 .

[21]  D. Agnew,et al.  Present-day crustal deformation in southern California , 1994 .

[22]  Andrea Donnellan,et al.  Geodetic measurement of deformation in the Ventura basin region , 1993 .

[23]  J. C. Savage,et al.  Strain accumulation north of Los Angeles, California, as a function of time, 1977-1992 , 1994 .

[24]  J. C. Savage,et al.  An apparent shear zone trending north-northwest across the Mojave Desert into Owens Valley, eastern , 1990 .

[25]  T. Davis,et al.  Seismically active fold and thrust belt in the San Joaquin Valley, central California , 1988 .

[26]  Amos Nur,et al.  Postseismic Viscoelastic Rebound , 1974, Science.

[27]  J. C. Savage,et al.  Interseismic deformation along the San Andreas Fault in southern California , 1995 .

[28]  R. Snay,et al.  Crustal velocity field near the big bend of California's , 1996 .

[29]  C. Cramer,et al.  Preliminary seismic hazard assessment for Los Angeles, Ventura, and Orange counties, California, affected by the 17 January 1994 Northridge earthquake , 1996, Bulletin of the Seismological Society of America.

[30]  C. Scholz,et al.  Strain localization along the San Andreas Fault: Consequences for loading mechanisms , 1994 .

[31]  David D. Jackson,et al.  A Bayesian approach to nonlinear inversion , 1985 .

[32]  W. Prescott,et al.  Geodetic measurements near Parkfield, California, 1959–1984 , 1987 .

[33]  K. Sieh,et al.  Prospects for Larger or More Frequent Earthquakes in the Los Angeles Metropolitan Region , 1995, Science.

[34]  R. Clayton,et al.  A tomographic image of mantle structure beneath Southern California , 1984 .

[35]  E. Hauksson.  Earthquakes, faulting, and stress in the Los Angeles Basin , 1990 .

[36]  G. Biasi,et al.  Quantitative Refinement of Calibrated 14C Distributions , 1994, Quaternary Research.

[37]  William H. Prescott,et al.  An extension of Frank's method for obtaining crustal shear strains from survey data , 1976 .

[38]  J. C. Savage,et al.  Precision of geodolite distance measurements for determining fault movements , 1973 .

[39]  Y. Okada.  Surface deformation due to shear and tensile faults in a half-space , 1985 .

[40]  David R. Brillinger,et al.  A more precise chronology of earthquakes produced by the San Andreas fault in southern California , 1989 .

[41]  Y. Okada.  Internal deformation due to shear and tensile faults in a half-space , 1992, Bulletin of the Seismological Society of America.

[42]  J. C. Savage,et al.  The velocity field along the San Andreas Fault in central and southern California , 1991 .

[43]  M. Zoback,et al.  Crustal strain near the Big Bend of the San Andreas Fault: Analysis of the Los Padres‐Tehachapi Trilateration Networks, California , 1990 .

[44]  R. Snay,et al.  Regional deformation of the earth model for the Los Angeles region, California , 1984 .

[45]  J. Rice,et al.  Crustal deformation in great California earthquake cycles , 1986 .

[46]  Sean C. Solomon,et al.  Geodetic slip rate for the eastern California shear zone and the recurrence time of Mojave desert earthquakes , 1994, Nature.

[47]  John H. Shaw,et al.  Earthquake hazards of active blind-thrust faults under the central Los Angeles basin , 1996 .

[48]  L. Jones.  Focal mechanisms and the state of stress on the San Andreas Fault in southern California , 1988 .

[49]  William E. Carter,et al.  The accuracy of astronomic azimuth determinations , 1978 .

[50]  A. Michelson.  Measurement of the Velocity of Light Between Mount Wilson and Mount San Antonio , 1927 .

[51]  D. Jackson,et al.  Crustal and uppermost mantle structure under southern California , 1992 .

[52]  R. Clayton,et al.  Lateral velocity variations in southern California. I. Results for the upper crust from Pg waves , 1986 .

[53]  S. Solomon,et al.  Geodetic Measurement of Deformation East of the San Andreas Fault in Central California , 1988 .

[54]  Wayne Thatcher,et al.  Nonlinear strain buildup and the earthquake cycle on the San Andreas Fault , 1983 .

[55]  J. C. Savage,et al.  Asthenosphere readjustment and the earthquake cycle , 1978 .

[56]  Richard G. Gordon,et al.  No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1 , 1991 .

[57]  Joseph L. Kirschvink,et al.  Paleomagnetic measurement of nonbrittle coseismic deformation across the San Andreas Fault at Pallett Creek , 1992 .

[58]  T. Atwater.  Plate tectonic history of the northeast Pacific and western North America , 1989 .