| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
U.S. GEOLOGICAL SURVEY, 345 MIDDLEFIELD ROAD, MENLO PARK, CALIFORNIA 94025
Abstract
The 1979 Imperial Valley, California, earthquake (Ms = 6.9) was recorded on the El Centro differential array, a 213-m-long linear array of 5 three-component digital accelerometers 5.6 km from the nearest tectonic surface rupture. Although absolute time was not recorded on the array elements, a relative time base was established using the main shock hypocentral P wave and the P and S waves from a later aftershock. A cross-correlation technique was used to measure the difference in arrival times of individual seismic waves in a moving 0.6 to 1.2 sec window at each array element, which would then be converted into the wave's slowness (1/velocity) along the array. When applied to the main shock vertical and horizontal accelerograms, results from both components of motion indicated that the early arriving energy came from a source to the south of the array, and the source of the energy moved rapidly to the north of the array during the strong shaking. The ground motions at the array elements were well correlated for about the first 11 sec of motion. These observations suggest that we have observed the initiation of rupture south of the array and its subsequent propagation along the fault to a position north of the array in about 10 sec, and that the energy was radiated from a fairly compact region around the rupture front. If the observed vertical and horizontal ground motions are assumed to be caused by P and S waves, respectively, then the observed slownesses show irregularities which can be interpreted as implying that the observed high-frequency ground motions originated at irregularly distributed regions on the fault surface, or that the rupture velocity was variable, or both. One possible interpretation of the data suggests that the rupture proceeded at near P-wave velocity over a 7-km-long section of fault. Average rupture velocities of about 2.7 to 3.2 km/sec at 8 km depth are consistent with the data, and 2.8 km/sec is weakly preferred under the assumption that rupture propagates at a fixed fraction of the shear velocity. The large vertical pulse, which had a peak acceleration of 1.7 g at E06, was emitted from the portion of the fault extending 25 to 30 km northwest of the hypocenter near Meloland overpass, and not from the point on the fault closest to the differential array. Nothing can be said about fault behavior southeast of the hypocenter.
This article has been cited by other articles:
|
|
 |
|
  S. Hartzell, P. Liu, C. Mendoza, C. Ji, and K. M. Larson Stability and Uncertainty of Finite-Fault Slip Inversions: Application to the 2004 Parkfield, California, Earthquake Bulletin of the Seismological Society of America, December 1, 2007; 97(6): 1911 - 1934. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Iida and K. Hatayama Effects of Seawater of Tokyo Bay on Short-Period Strong Ground Motion Bulletin of the Seismological Society of America, August 1, 2007; 97(4): 1324 - 1333. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. B. Fletcher, P. Spudich, and L. M. Baker Rupture Propagation of the 2004 Parkfield, California, Earthquake from Observations at the UPSAR Bulletin of the Seismological Society of America, September 1, 2006; 96(4B): S129 - S142. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. T. Aagaard and T. H. Heaton Near-Source Ground Motions from Simulations of Sustained Intersonic and Supersonic Fault Ruptures Bulletin of the Seismological Society of America, December 1, 2004; 94(6): 2064 - 2078. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. Xia, A. J. Rosakis, and H. Kanamori Laboratory Earthquakes: The Sub-Rayleigh-to-Supershear Rupture Transition Science, March 19, 2004; 303(5665): 1859 - 1861. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Bouchon and M. Vallee Observation of Long Supershear Rupture During the Magnitude 8.1 Kunlunshan Earthquake Science, August 8, 2003; 301(5634): 824 - 826. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Space and Time Evolution of Rupture and Faulting during the 1999 Izmit (Turkey) Earthquake Bulletin of the Seismological Society of America, February 1, 2002; 92(1): 256 - 266.
|
|
|
|
|
|
What Can Strong-Motion Data Tell Us about Slip-Weakening Fault-Friction Laws? Bulletin of the Seismological Society of America, February 1, 2000; 90(1): 98 - 116.
|
|
|
|
|
|
Y. Ben-Zion and D. J. Andrews Properties and implications of dynamic rupture along a material interface Bulletin of the Seismological Society of America, August 1, 1998; 88(4): 1085 - 1094. [Abstract] [PDF]
|
|
|
|
|
|
W. L. Ellsworth, W. L. Ellsworth, and G. C. Beroza Seismic Evidence for an Earthquake Nucleation Phase Science, May 12, 1995; 268(5212): 851 - 855. [Abstract] [PDF]
|
|
|
|
|
|
M.-P. Bouin and P. Bernard Analysis of strong-motion S wave polarization of the 15 October 1979 Imperial Valley earthquake Bulletin of the Seismological Society of America, December 1, 1994; 84(6): 1770 - 1785. [Abstract] [PDF]
|
|
|
|
|
|
S. H. Hartzell, D. L. Carver, and K. W. King Initial investigation of site and topographic effects at Robinwood Ridge, California Bulletin of the Seismological Society of America, October 1, 1994; 84(5): 1336 - 1349. [Abstract] [PDF]
|
|
|
|
|
|
R. Abercrombie and J. Mori Local observations of the onset of a large earthquake: 28 June 1992 Landers, California Bulletin of the Seismological Society of America, June 1, 1994; 84(3): 725 - 734. [Abstract] [PDF]
|
|
|
|
|
|
J. B. FLETCHER, L. M. BAKER, P. SPUDICH, P. GOLDSTEIN, J. D. SIMS, and M. HELLWEG The USGS Parkfield, California, dense seismograph array: Upsar Bulletin of the Seismological Society of America, April 1, 1992; 82(2): 1041 - 1070. [Abstract] [PDF]
|
|
|
|
|
|
W. B. JOYNER Directivity for nonuniform ruptures Bulletin of the Seismological Society of America, August 1, 1991; 81(4): 1391 - 1395. [PDF]
|
|
|
|
|
|
M. IIDA, T. MIYATAKE, and K. SHIMAZAKI Relationship between strong-motion array parameters and the accuracy of source inversion and physical waves Bulletin of the Seismological Society of America, December 1, 1990; 80(6A): 1533 - 1552. [Abstract] [PDF]
|
|
|
|
|
|
J.-C. GARIEL, R. J. ARCHULETA, and M. BOUCHON Rupture process of an earthquake with kilometric size fault inferred from the modeling of near-source records Bulletin of the Seismological Society of America, August 1, 1990; 80(4): 870 - 888. [Abstract] [PDF]
|
|
|
|
|
|
A. FRANKEL and L. WENNERBERG Rupture process of the Ms 6.6 Superstition Hills, California, earthquake determined from strong-motion recordings: Application of tomographic source inversion Bulletin of the Seismological Society of America, April 1, 1989; 79(2): 515 - 541. [Abstract] [PDF]
|
|
|
|
|
|
E. CRANSWICK, R. WETMILLER, and J. BOATWRIGHT High-frequency observations and source parameters of microearthquakes recorded at hard-rock sites Bulletin of the Seismological Society of America, December 1, 1985; 75(6): 1535 - 1567. [Abstract] [PDF]
|
|
|
|
|
|
N. A. ABRAHAMSON and B. A. BOLT The spatial variation of the phasing of seismic strong ground motion Bulletin of the Seismological Society of America, October 1, 1985; 75(5): 1247 - 1264. [Abstract] [PDF]
|
|
|
|
|
|
P. SPUDICH and L. N. FRAZER Use of ray theory to calculate high-frequency radiation from earthquake sources having spatially variable rupture velocity and stress drop Bulletin of the Seismological Society of America, December 1, 1984; 74(6): 2061 - 2082. [Abstract] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
