Locking depths estimated from geodesy and seismology along the San Andreas Fault System: Implications for seismic moment release

[1] The depth of the seismogenic zone is a critical parameter for earthquake hazard models. Independent observations from seismology and geodesy can provide insight into the depths of faulting, but these depths do not always agree. Here we inspect variations in fault depths of 12 segments of the southern San Andreas Fault System derived from over 1000 GPS velocities and 66,000 relocated earthquake hypocenters. Geodetically determined locking depths range from 6 to 22 km, while seismogenic thicknesses are largely limited to depths of 11–20km.Theseseismogenicdepthsbestmatchthegeodeticlockingdepthswhenestimated at the 95% cutoff depth in seismicity, and most fault segment depths agree to within 2 km. However, the Imperial, Coyote Creek, and Borrego segments have significant discrepancies. In these cases the geodetically inferred locking depths are much shallower than the seismogenic depths. We also examine variations in seismic moment accumulation rate per unit fault length as suggested by seismicity and geodesy and find that both approaches yield high rates (1.5– 1.8 ×1 0 13 Nm/yr/km) along the Mojave and Carrizo segments and low rates (∼0.2 × 10 13 Nm/yr/km) along several San Jacinto segments. The largest difference in seismic moment between models is calculated for the Imperial segment, where the moment rate from seismic depths is a factor of ∼2.5 larger than that from geodetic depths. Such variability has important implications for the accuracy to which future major earthquake magnitudes can be estimated.

[1]  David T. Sandwell,et al.  Optimal combination of InSAR and GPS for measuring interseismic crustal deformation , 2010 .

[2]  S. Wdowinski.  Deep creep as a cause for the excess seismicity along the San Jacinto fault , 2009 .

[3]  D. Sandwell,et al.  Stress evolution of the San Andreas fault system: Recurrence interval versus locking depth , 2009 .

[4]  Timothy E. Dawson,et al.  Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) , 2009 .

[5]  Paul Bodin,et al.  Widespread Triggering of Nonvolcanic Tremor in California , 2008, Science.

[6]  P. Shearer,et al.  Applying a three-dimensional velocity model, waveform cross correlation, and cluster analysis to locate southern California seismicity from 1981 to 2005 , 2007 .

[7]  Jerome A. Treiman,et al.  Community Fault Model (CFM) for Southern California , 2007 .

[8]  Yuri Fialko,et al.  Interseismic strain accumulation and the earthquake potential on the southern San Andreas fault system , 2006, Nature.

[9]  T. Dixon,et al.  Strain accumulation across the Carrizo segment of the San Andreas Fault, California : Impact of laterally varying crustal properties , 2006 .

[10]  J. C. Savage.  Dislocation pileup as a representation of strain accumulation on a strike‐slip fault , 2006 .

[11]  D. Sandwell,et al.  A model of the earthquake cycle along the San Andreas Fault System for the past 1000 years , 2006 .

[12]  Robert McCaffrey,et al.  Block kinematics of the Pacific-North America plate boundary in the southwestern United States from inversion of GPS, seismological, and geologic data , 2005 .

[13]  Brendan J. Meade,et al.  Block models of crustal motion in southern California constrained by GPS measurements , 2005 .

[14]  Jeanne L. Hardebeck,et al.  Constraints on fault slip rates of the southern California plate boundary from GPS velocity and stress inversions , 2005 .

[15]  R. Nadeau,et al.  Nonvolcanic Tremors Deep Beneath the San Andreas Fault , 2005, Science.

[16]  H. Hirose,et al.  Episodic slow slip events accompanied by non‐volcanic tremors in southwest Japan subduction zone , 2004 .

[17]  B. Meade,et al.  Spatial localization of moment deficits in southern California , 2004 .

[18]  K. Furlong,et al.  Codependent histories of the San Andreas and San Jacinto fault zones from inversion of fault displacement rates , 2004 .

[19]  E. Hauksson,et al.  The Seismogenic Thickness of the Southern California Crust , 2004 .

[20]  B. Meade,et al.  Viscoelastic deformation for a clustered earthquake cycle , 2004 .

[21]  Glenn P. Biasi,et al.  Wrightwood and the earthquake cycle: What a long recurrence record tells us about how faults work , 2004 .

[22]  P. A. Bedrosiana,et al.  Geophysical images of the creeping segment of the San Andreas fault : implications for the role of crustal fluids in the earthquake process , 2004 .

[23]  D. Blackwell,et al.  Thermal Constraints on Earthquake Depths in California , 2003 .

[24]  R. Bürgmann,et al.  The evolution of the seismic‐aseismic transition during the earthquake cycle: Constraints from the time‐dependent depth distribution of aftershocks , 2003 .

[25]  Kerry E Sieh,et al.  Complexities of the San Andreas fault near San Gorgonio Pass: Implications for large earthquakes , 2003 .

[26]  H. Dragert,et al.  Episodic Tremor and Slip on the Cascadia Subduction Zone: The Chatter of Silent Slip , 2003, Science.

[27]  David T. Sandwell,et al.  Fault creep along the southern San Andreas from interferometric synthetic aperture radar, permanent scatterers, and stacking , 2003 .

[28]  Yehuda Bock,et al.  Creep along the Imperial Fault, southern California, from GPS measurements , 2002 .

[29]  P. Segall.  Integrating Geologic and Geodetic Estimates of Slip Rate on the San Andreas Fault System , 2002 .

[30]  H. Magistrale.  Relative contributions of crustal temperature and composition to controlling the depth of earthquakes in Southern California , 2001 .

[31]  David T. Sandwell,et al.  Variations in Coulomb Stress Accumulation Along the San Andreas Fault System , 2001 .

[32]  P. Shearer.  Parallel fault strands at 9‐km depth resolved on the Imperial Fault, Southern California , 2001 .

[33]  W. Prescott,et al.  Inversion of GPS data for spatially variable slip‐rate on the San Andreas Fault near Parkfield, CA , 2001 .

[34]  R. Bürgmann,et al.  Earthquake potential along the northern hayward fault, california , 2000, Science.

[35]  Peter M. Shearer,et al.  Earthquake locations in southern California obtained using source‐specific station terms , 2000 .

[36]  P. Vincent.  Application of SAR interferometry to low-rate crustal deformation fields , 1998 .

[37]  J. C. Savage,et al.  Surface strain accumulation and the seismic moment tensor , 1997, Bulletin of the Seismological Society of America.

[38]  P. Rosen,et al.  Detection of aseismic creep along the San Andreas fault near Parkfield, California with ERS-1 radar interferometry , 1997 .

[39]  Yehuda Bock,et al.  Crustal deformation across the Imperial Fault: Results from kinematic GPS surveys and trilateration of a densely spaced, small‐aperture network , 1997 .

[40]  Hua-Wei Zhou,et al.  Lithologic Control of the Depth of Earthquakes in Southern California , 1996, Science.

[41]  Colin F. Williams.  Temperature and the Seismic/Aseismic Transition: Observations from the 1992 Landers Earthquake , 1996 .

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

[43]  William A. Bryant,et al.  Probabilistic seismic hazard assessment for the state of California , 1996 .

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

[45]  P. Bird,et al.  Computer simulations of California tectonics confirm very low strength of major faults , 1994 .

[46]  J. C. Savage.  Equivalent strike‐slip earthquake cycles in half‐space and lithosphere‐asthenosphere earth models , 1990 .

[47]  C. Sanders.  Earthquake depths and the relation to strain accumulation and stress near strike‐slip faults in southern California , 1990 .

[48]  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 .

[49]  K. Furlong,et al.  Thermal-mechanical controls on seismicity depth distributions in the San Andreas Fault Zone , 1988 .

[50]  Chris Marone,et al.  The depth of seismic faulting and the upper transition from stable to unstable slip regimes , 1988 .

[51]  P. Segall,et al.  Detection of a locked zone at depth on the Parkfield, California, segment of the San Andreas Fault , 1987 .

[52]  S. Larsen,et al.  Vertical crustal deformation associated with the 1979 M = 6.6 Imperial Valley, California Earthquake: Implications for fault behavior , 1986 .

[53]  H. Kanamori,et al.  Depth of seismicity in the Imperial Valley Region (1977–1983) and its relationship to heat flow, crustal structure and the October 15, 1979, earthquake , 1986 .

[54]  A. Lachenbruch,et al.  Heat flow in southernmost California and the origin of the Salton Trough , 1985 .

[55]  Ray J. Weldon,et al.  Holocene rate of slip and tentative recurrence interval for large earthquakes on the San Andreas fault, Cajon Pass, southern California , 1985 .

[56]  C. R. Allen,et al.  Fault slip in southern California , 1985 .

[57]  Ralph J. Archuleta,et al.  A faulting model for the 1979 Imperial Valley earthquake , 1984 .

[58]  Shamita Das,et al.  Why large earthquakes do not nucleate at shallow depths , 1983, Nature.

[59]  George A. McMechan,et al.  Crustal structure of the Imperial Valley region. , 1982 .

[60]  Robert V. Sharp,et al.  Variable rates of late Quaternary strike slip on the San Jacinto fault zone, southern California , 1981 .

[61]  W. Thatcher.  Systematic inversion of geodetic data in central California , 1979 .

[62]  C. R. Allen,et al.  Large creep events on the Imperial fault, California , 1978, Bulletin of the Seismological Society of America.

[63]  J. C. Savage,et al.  Geodetic determination of relative plate motion in central California , 1973 .

[64]  W. Brace,et al.  California Earthquakes: Why Only Shallow Focus? , 1970, Science.

[65]  Y. Morrison.  presented at the Annual Meeting of the , 1970 .

[66]  J. C. Crowell.  The San Andreas Fault in Southern California , 1958 .