Future Seismic Hazards in southern California: Phase I: Implications of the 1992 Landers Earthquake Sequence

Southern California and its seismologists received a wake-up call on June 28, 1992. The largest earthquake to strike southern California in 40 years occurred near the town of Landers, located 30 km north of the San Andreas fault. It had a magnitude of 7.5 (M7.5). Three and one-half hours later, a M6.5 aftershock struck the Big Bear area 40 km (kilometers) to the west of Landers. An ad hoc working group was rapidly convened in July, 1992, to evaluate how the Landers-Big Bear earthquake sequence might affect future large earthquakes along major faults in southern California. In particular, what are the chances of large earthquakes in the next few years and how do they compare to previous estimates (such as those of the Working Group on California Earthquake Probabilities -- WGCEP, 1988)? Such an evaluation was made for central California after the Lorna Prieta earthquake of 1989 (WGCEP, 1990). The charge to the Landers ad hoc working group included analyzing the seismicity for the last several years in southern California and the new paleoseismic, geologic, and geodetic data recently available for southern California. To inform the public about the potential hazard of plausible earthquakes, the working group was also asked to map the predicted severity of ground shaking for such earthquakes compared to that from the Landers earthquake.

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

[2]  Lynn R. Sykes,et al.  Changes in State of Stress on the Southern San Andreas Fault Resulting from the California Earthquake Sequence of April to June 1992 , 1992, Science.

[3]  Jian Lin,et al.  Change in Failure Stress on the Southern San Andreas Fault System Caused by the 1992 Magnitude = 7.4 Landers Earthquake , 1992, Science.

[4]  R. Simpson,et al.  Changes in static stress on southern California faults after the 1992 Landers earthquake , 1992, Nature.

[5]  Javier F. Pacheco,et al.  Seismic moment catalog of large shallow earthquakes, 1900 to 1989 , 1992, Bulletin of the Seismological Society of America.

[6]  Lucile M. Jones,et al.  Prediction Probabilities From Foreshocks , 1991 .

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

[8]  Roy K. Dokka,et al.  Role of the Eastern California Shear Zone in accommodating Pacific‐North American Plate motion , 1990 .

[9]  P. Reasenberg,et al.  Earthquake Hazard After a Mainshock in California , 1989, Science.

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

[11]  J. Dieterich.  Probability of earthquake recurrence with nonuniform stress rates and time-dependent failure , 1988 .

[12]  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 .

[13]  A. Dziewoński,et al.  Centroid-moment tensor solutions for July-September, 1983 , 1984 .

[14]  Roy K. Dokka,et al.  Displacements on late Cenozoic strike-slip faults of the central Mojave Desert, California , 1983 .

[15]  K. Steinbrugge,et al.  Earthquakes, Volcanoes and Tsunamis: An Anatomy of Hazards , 1982 .

[16]  Kerry E Sieh,et al.  Prehistoric large earthquakes produced by slip on the San Andreas Fault at Pallett Creek, California , 1978 .

[17]  Yan Y. Kagan,et al.  Long-term earthquake clustering , 1991 .

[18]  William L. Ellsworth,et al.  Earthquake history, 1769-1989 , 1990 .

[19]  J. Hagan,et al.  Earthquake History of the Simi Valley Area, California , 1983 .

[20]  W. M. Kohler,et al.  Seismic intensities of earthquakes of conterminous United States; their prediction and interpretation , 1981 .

[21]  F. K. Miller,et al.  Photoreconnaissance maps showing young-looking fault features in the southern Mojave Desert, California , 1980 .