|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
U.S. GEOLOGICAL SURVEY, 345 MIDDLEFIELD ROAD, MS 77, MENLO PARK, CALIFORNIA 94025
Abstract
The compressional-wave velocity structure of the crust of the Coast Ranges of central California was modeled from seismic refraction data reported previously. For both the Diablo Range (east of the San Andreas fault) and the Gabilan Range (west of the fault), two alternative velocity models were derived for each range by iterative two-dimensional ray tracing. Each pair of models shows a sedimentary layer and an underlying crust composed of three or four layers. For the Diablo Range, the velocities in the sediments range from 2.9 to 4.8 km/sec, and the depth to basement varies from 0.2 km within the central Diablo Range to a maximum of 3.4 km north of the Livermore Valley. In the Gabilan Range, the velocities in the sediments overlying the granitic basement are higher north of the Gabilan Range (3.6 to 4.6 km/sec) than to the south (2.2 to 3.8 km/sec), and the depth to basement both north and south of the range is less than 2 km.
Below the sediments and fractured near-surface material, a resolvable difference in the crustal velocity structure on opposite sides of the San Andreas fault indicates compositional differences at depth. The upper crust has an average velocity of 5.7 km/sec at depths between 3 and 16 ± 3 km in the Diablo Range and an average velocity of 6.1 km/sec at depths between 2 and 9 ± 1 km in the Gabilan Range. The lower crust has an average velocity of 6.9 km/sec at depths between 16 ± 3 and 30 km in the Diablo Range and an average velocity of 6.5 km/sec at depths between 10 and 24 km in the Gabilan Range. The models also show that the depth to Moho differs by several kilometers between the two ranges. In the Diablo Range models, the crust-mantle boundary becomes shallower from south to north, rising from a depth of 30 to 26 km. In the Gabilan Range models, the Moho is at a depth of 24 to 26 km, depending on the velocity assumed at the base of the crust.
Laboratory measurements of rock velocities and the mapped surface geology allow us to interpret the velocity models in terms of crustal composition. We conclude that the Diablo Range probably consists largely of metagraywacke to a depth of 16 ± 3 km, and gabbroic material below this depth. The crust of the Gabilan Range probably consists of granitic material to a depth of 9 ± 1 km and gneissic material below this depth. Franciscan rocks are not regionally present in the crust of the Gabilan Range. If the gneissic lower crust consists of the same rocks as are found at the surface in the Gabilan Range, then the presumed large-scale lateral motion of the Salinian block has taken place at or below the crust-mantle boundary, rather than along a mid-crustal slip plane.
This article has been cited by other articles:
|
|
 |
|
  K.-S. Liu and Y.-B. Tsai Large Effects of Moho Reflections (SmS) on Peak Ground Motion in Northwestern Taiwan Bulletin of the Seismological Society of America, February 1, 2009; 99(1): 255 - 267. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Hardebeck, A. J. Michael, and T. M. Brocher Seismic Velocity Structure and Seismotectonics of the Eastern San Francisco Bay Region, California Bulletin of the Seismological Society of America, June 1, 2007; 97(3): 826 - 842. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Lomax A Reanalysis of the Hypocentral Location and Related Observations for the Great 1906 California Earthquake Bulletin of the Seismological Society of America, June 1, 2005; 95(3): 861 - 877. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. J. McGuire Estimating Finite Source Properties of Small Earthquake Ruptures Bulletin of the Seismological Society of America, April 1, 2004; 94(2): 377 - 393. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Peltzer, F. Crampé, and G. King Evidence of Nonlinear Elasticity of the Crust from the Mw7.6 Manyi (Tibet) Earthquake Science, October 8, 1999; 286(5438): 272 - 276. [Abstract] [Full Text]
|
|
|
|
|
|
C. Stidham, M. Antolik, D. Dreger, S. Larsen, and B. Romanowicz Three-dimensional structure influences on the strong-motion wavefield of the 1989 Loma Prieta earthquake Bulletin of the Seismological Society of America, October 1, 1999; 89(5): 1184 - 1202. [Abstract] [PDF]
|
|
|
|
|
|
E. Shalev and J. M. Lees Cubic B-splines tomography at Loma Prieta Bulletin of the Seismological Society of America, February 1, 1998; 88(1): 256 - 269. [Abstract] [PDF]
|
|
|
|
|
|
K.-H. Yoon and G. A. McMechan 3D eight-order elastic finite-difference modeling of refraction and strong-motion data from the Coyote Lake region, California Bulletin of the Seismological Society of America, June 1, 1996; 86(3): 616 - 626. [Abstract] [PDF]
|
|
|
|
|
|
T. M. Brocher, T. M. Brocher, J. McCarthy, P. E. Hart, W. S. Holbrook, K. P. Furlong, T. V. McEvilly, J. A. Hole, and S. L. Klemperer Seismic Evidence for a Lower-Crustal Detachment Beneath San Francisco Bay, California Science, September 2, 1994; 265(5177): 1436 - 1439. [Abstract] [PDF]
|
|
|
|
|
|
H. KANAMORI and E. HAUKSSON A slow earthquake in the Santa Maria basin, California Bulletin of the Seismological Society of America, October 1, 1992; 82(5): 2087 - 2096. [Abstract] [PDF]
|
|
|
|
|
|
R. H. COLBURN and R. B. HAWMAN Inversion of slant stacks of deep crustal refraction data from the Great Valley, California Bulletin of the Seismological Society of America, October 1, 1992; 82(5): 2224 - 2247. [Abstract] [PDF]
|
|
|
|
|
|
T. C. WALLACE, A. VELASCO, J. ZHANG, and T. LAY A broadband seismological investigation of the 1989 Loma Prieta, California, earthquake: Evidence for deep slow slip? Bulletin of the Seismological Society of America, October 1, 1991; 81(5): 1622 - 1646. [Abstract] [PDF]
|
|
|
|
|
|
Y. Ben-Zion, Y. BEN-ZION, and P. MALIN San Andreas Fault Zone Head Waves Near Parkfield, California Science, March 29, 1991; 251(5001): 1592 - 1594. [Abstract] [PDF]
|
|
|
|
|
|
Y.-G. LI and P. C. LEARY Fault zone trapped seismic waves Bulletin of the Seismological Society of America, October 1, 1990; 80(5): 1245 - 1271. [Abstract] [PDF]
|
|
|
|
|
|
N. MACGREGOR-SCOTT and A. WALTER Crustal velocities near Coalinga, California, modeled from a combined earthquake/explosion refraction profile Bulletin of the Seismological Society of America, August 1, 1988; 78(4): 1475 - 1490. [Abstract] [PDF]
|
|
|
|
|
|
A. S. MELTZER, A. R. LEVANDER, and W. D. MOONEY Upper crustal structure, Livermore Valley and vicinity, California coast ranges Bulletin of the Seismological Society of America, October 1, 1987; 77(5): 1655 - 1673. [Abstract] [PDF]
|
|
|
|
|
|
R. W. BURGER, P. G. SOMERVILLE, J. S. BARKER, R. B. HERRMANN, and D. V. HELMBERGER The effect of crustal structure on strong ground motion attenuation relations in eastern North America Bulletin of the Seismological Society of America, April 1, 1987; 77(2): 420 - 439. [Abstract] [PDF]
|
|
|
|
|
|
J. H. MCBRIDE and L. D. BROWN Reanalysis of the cocorp deep seismic reflection profile across the San Andreas fault, Parkfield, California Bulletin of the Seismological Society of America, December 1, 1986; 76(6): 1668 - 1686. [Abstract] [PDF]
|
|
|
|
|
|
R. H. COLBURN and W. D. MOONEY Two-dimensional velocity structure along the synclinal axis of the Great Valley, California Bulletin of the Seismological Society of America, October 1, 1986; 76(5): 1305 - 1322. [Abstract] [PDF]
|
|
|
|
|
|
L. J. HWANG and W. D. MOONEY Velocity and Q structure of the Great Valley, California, based on synthetic seismogram modeling of seismic refraction data Bulletin of the Seismological Society of America, August 1, 1986; 76(4): 1053 - 1067. [Abstract] [PDF]
|
|
|
|
|
|
W. D. MOONEY and R. H. COLBURN A seismic-refraction profile across the San Andreas, Sargent, and Calaveras faults, west-central California Bulletin of the Seismological Society of America, February 1, 1985; 75(1): 175 - 191. [Abstract] [PDF]
|
|
|
|
|
|
P. BLUMLING, W. D. MOONEY, and W. H. K. LEE Crustal structure of the southern Calaveras fault zone, central California, from seismic refraction investigations Bulletin of the Seismological Society of America, February 1, 1985; 75(1): 193 - 209. [Abstract] [PDF]
|
|
|
|
|
|
W. H. BAKUN and W. B. JOYNER The ML scale in central California Bulletin of the Seismological Society of America, October 1, 1984; 74(5): 1827 - 1843. [Abstract] [PDF]
|
|
|
|
|
|
R. FENG and T. V. MCEVILLY Interpretation of seismic reflection profiling data for the structure of the San Andreas fault zone Bulletin of the Seismological Society of America, December 1, 1983; 73(6A): 1701 - 1720. [Abstract] [PDF]
|
|
|
|
|
|
A. R. LEVANDER, H. QUIN, and R. L. KOVACH Shear wave observations in the region north of the San Francisco Bay Bulletin of the Seismological Society of America, August 1, 1983; 73(4): 1031 - 1039. [Abstract] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
