Patterns of seismic release in the southern California region

Southern California experiences earthquakes on the San Andreas system of vertical right-lateral predominantly strike-slip faults and on a second system of faults that includes thrusts, oblique-slip, left-lateral, and other faults. Pattern recognition and cluster analysis are used to analyze the catalog of earthquakes with magnitudes ≥5.5 from 1915 to 1994. We use pattern recognition to find a suite of traits that would characterize each of these two systems and distinguish them from each other. Both pattern recognition and cluster analysis show that epochs of seismic release occur in which one or the other system is the predominant form of earthquake activity. For the past 2 decades the second system has been the active one. Small changes in the direction of plate movements could account for this phenomenon. Seismic release on the San Andreas system is preceded by episodes of activity in the Great Basin or in the Gulf of California. Presumably, these episodes would represent extension in the former region and spreading and slip on transform faults in the latter.

[1]  W. Thatcher,et al.  Aftershocks and source characteristics of the 1969 Coyote Mountain earthquake, San Jacinto Fault zone, California , 1973, Bulletin of the Seismological Society of America.

[2]  I. Selwyn Sacks,et al.  Increased pressure from rising bubbles as a mechanism for remotely triggered seismicity , 1994, Nature.

[3]  J. Ebel,et al.  The source mechanism of the August 7, 1966 El Golfo earthquake , 1978, Bulletin of the Seismological Society of America.

[4]  C. Johnson,et al.  The Santa Barbara, California, earthquake of 13 August 1978 , 1982 .

[5]  W. Thatcher.  Regional variations of seismic source parameters in the northern Baja California area , 1972 .

[6]  J. C. Branner.  The Tejon Pass earthquake of October 22, 1916 , 1917, Bulletin of the Seismological Society of America.

[7]  W. Thatcher,et al.  Seismic and aseismic deformation associated with the 1952 Kern County, California, earthquake and relationship to the quaternary history of the White Wolf fault , 1981 .

[8]  T. Hanks,et al.  Seismic Moments of the Larger Earthquakes of the Southern California Region , 1975 .

[9]  G. Ekström,et al.  Seismicity and geometry of a 110 km-long blind thrust fault: 1 , 1992 .

[10]  Frank Press,et al.  Chandler Wobble, earthquakes, rotation, and geomagnetic changes , 1975, Nature.

[11]  E. Engdahl,et al.  Seismicity Map of North America Project , 1991 .

[12]  D. Doser.  Faulting processes of the 1956 San Miguel, Baja California, earthquake sequence , 1992 .

[13]  Kiyoo Mogi,et al.  4. Migration of Seismic Activity , 1968 .

[14]  K. Aki,et al.  Simultaneous determination of the seismic moment and attenuation of seismic surface waves , 1969 .

[15]  W. Ellsworth,et al.  Point Mugu, California, Earthquake of 21 February 1973 and Its Aftershocks , 1973, Science.

[16]  J. Goltz.  The Northridge, California Earthquake of January 17, 1994: General Reconnaissance Report , 1994 .

[17]  C. Richter.  The Manix (California) earthquake of April 10, 1947 , 1947 .

[18]  G. Shor,et al.  San Miguel, Baja California Norte, earthquakes of February, 1956: A field report , 1958 .

[19]  B. Romanowicz.  Spatiotemporal Patterns in the Energy Release of Great Earthquakes , 1993, Science.

[20]  P. Somerville,et al.  The location and source parameters of the Lompoc, California, earthquake of 4 November 1927 , 1992 .

[21]  Thomas H. Heaton,et al.  The 1971 San Fernando earthquake: A double event? , 1982 .

[22]  Jerome A. Treiman,et al.  Near-Field Investigations of the Landers Earthquake Sequence, April to July 1992 , 1993, Science.

[23]  Frank Press,et al.  Pattern recognition applied to earthquake epicenters in California and Nevada , 1977 .

[24]  Frank Press,et al.  Pattern recognition applied to earthquake epicenters in California , 1976 .

[25]  H. Kanamori,et al.  A moment magnitude scale , 1979 .

[26]  C. R. Allen,et al.  Intermediate-term prediction of occurrence times of strong earthquakes , 1988, Nature.

[27]  Thomas V. McEvilly,et al.  Recurrence models and Parkfield, California, earthquakes , 1984 .

[28]  Thomas H. Heaton,et al.  Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake , 1983 .

[29]  N Oreskes,et al.  Verification, Validation, and Confirmation of Numerical Models in the Earth Sciences , 1994, Science.

[30]  D. Doser.  Source characteristics of earthquakes along the southern San Jacinto and Imperial fault zones (1937 to 1954) , 1990, Bulletin of the Seismological Society of America.

[31]  Seismicity and fault interaction, Southern San Jacinto Fault Zone and adjacent faults, southern California: Implications for seismic hazard , 1991 .

[32]  Robert V. Sharp,et al.  Surface faulting along the Superstition Hills fault zone and nearby faults associated with the earthquakes of 24 November 1987 , 1989 .

[33]  Patrick L. Williams,et al.  Seismotectonics of the easternmost transverse ranges, California: Relevance for seismic potential of the southern San Andreas Fault , 1990 .

[34]  Herbert A. Simon.  Scientific discovery as problem solving , 1992 .

[35]  I. Sacks,et al.  Asthenospheric viscosity inferred from correlated land–sea earthquakes in north-east Japan , 1988, Nature.

[36]  Migration of Seismic Activity , 1974 .

[37]  C. R. Allen,et al.  The July 1986 North Palm Springs, California, Earthquake - The North Palm Springs, California, Earthquake Sequence of July 1986 , 1986 .

[38]  C. R. Allen,et al.  San Fernando Earthquake series, 1971: Focal mechanisms and tectonics , 1973 .

[39]  C. R. Allen,et al.  Relationship between seismicity and geologic structure in the Southern California region , 1965 .

[40]  The 1987 Whittier Narrows Earthquake in the Los Angeles Metropolitan Area, California , 1988, Science.

[41]  John G. Anderson,et al.  Earthquake recurrence models and historical seismicity in the Mexicali-Imperial Valley , 1987 .

[42]  D. Doser.  Contrasts between source parameters of M⩾5.5 earthquakes in northern Baja California and southern California , 1993 .

[43]  Egill Hauksson,et al.  Source parameters of the 1933 Long Beach earthquake , 1991 .

[44]  R. E. Wallace,et al.  The Parkfield-Cholame, California, earthquakes of June-August 1966 - surface geologic effects, water-resources aspects, and preliminary seismic data , 1967 .

[45]  M. Zoback,et al.  New Evidence on the State of Stress of the San Andreas Fault System , 1987, Science.

[46]  Lucile M. Jones,et al.  Local magnitudes and apparent variations in seismicity rates in Southern California , 1993 .

[47]  Historic earthquakes (1918 to 1923) and an assessment of source parameters along the San Jacinto fault system , 1992 .

[48]  H. Kanamori,et al.  Seismicity near Palmdale, California, and its relation to strain changes , 1983 .

[49]  W. Ellsworth,et al.  Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake , 1993, Science.

[50]  G. Ekström,et al.  Seismicity and geometry of a 110‐km‐long blind thrust fault 2. Synthesis of the 1982–1985 California Earthquake Sequence , 1992 .

[51]  Robert V. Sharp,et al.  Surface faulting in the central Imperial Valley: in The Imperial Valley, California Earthquake of October 15, 1979 , 1982 .

[52]  H. Kanamori,et al.  The Superstition Hills, California, earthquakes of 24 November 1987 , 1989 .

[53]  H. Kanamori,et al.  Source mechanisms of twenty-six large, shallow earthquake (MS ≧ 6.5) during 1980 from P-wave first motion and long-period Rayleigh wave data , 1984 .