1948 Desert Hot Springs earthquake
|Date||December 4, 1948|
|Origin time||15:43 PST|
|Magnitude||6.3 ML |
|Depth||12 km (7.5 mi) |
|Areas affected||Southern California
|Max. intensity||VII (Very Strong) |
The 1948 Desert Hot Springs earthquake occurred on December 4 at 3:43 p.m. Pacific Standard Time with a Richter magnitude of 6.3 and a maximum perceived intensity of VII (Very Strong). The shock was felt from the central coast of California in the north, and to Baja California in the south, and came at a time when earthquake research in southern California was being resumed following the second world war. The earthquake was one of two that have occurred on the southern San Andreas Fault system in modern times, and although damage was not severe, some serious injuries occurred.
The United States' involvement in World War II brought about a lapse in earthquake research in California, due to scientists and other technicians being pulled away for defense-related work, and the ongoing process of using earthquake records to establish their epicenters eventually came to end. The Seismological Society of America cancelled their annual meetings and their Bulletin was reduced to half its normal size. In the late 1940s though, research resumed at the Caltech Seismological Laboratory in Pasadena and the University of California, Berkeley in the form of monitoring local earthquakes in order to detect the location of active faults. By 1948, Charles Richter had determined that areas where small earthquakes were occurring did not necessarily mean that a stronger shock would take place at the same location in the future.
The San Gorgonio Pass is the site of the largest irregularities of the San Andreas Fault system, where it becomes extraordinarily complex by branching into a group of discontinuous faults. The convoluted nature of the fault strands there makes estimating the source characteristics of future events in that area challenging. Simultaneous rupture of multiple fault strands can produce exceptionally complex earthquakes, like the 1992 Landers earthquake, which was caused by sequential rupture of multiple strike-slip faults. The site of the 1989 Loma Prieta earthquake is another example of a simple fault within a relatively complex zone. That shock occurred on an unexposed and unknown strike-slip/reverse fault that lies close in proximity to the San Andreas fault in the Santa Cruz Mountains.
The San Andreas fault system is similarly complex as it moves through the San Gorgonio Pass, with associated oblique reverse faults that are actively uplifting San Gorgonio Mountain, the tallest peak in southern California. The 1986 North Palm Springs earthquake occurred to the west of the 1948 shock, on the Garnet Hill fault or the Coachella strand of the Banning fault, with 9 km (5.6 mi) of surface rupture. Together, these are the only historical shocks to occur on the portion of the San Andreas fault system that lies south of the Cajon Pass.
The shock was felt as far north as Santa Maria and south into northern Baja California, and was described by seismologists as having been stronger than the 1933 Long Beach earthquake that heavily affected southern California, but no one was killed and only relatively minor damage occurred. A few injuries, some serious, occurred at the Palm Springs Theater during the rush to evacuate the building, and another man was injured by falling merchandise and required hospitalization. In downtown Los Angeles, buildings swayed, some windows were broken, and cracks appeared in some buildings. Similar types of damage was also present in Twentynine Palms, El Centro, and Yucca Valley.
- Nicholson, C. (1996), "Seismic behavior of the southern San Andreas fault zone in the northern Coachella Valley, California: Comparison of the 1948 and 1986 earthquake sequences", Bulletin of the Seismological Society of America (Seismological Society of America) 86 (5): 1331, 1338–1343
- Stover, C.W.; Coffman, J.L. (1993), Seismicity of the United States, 1568-1989 (Revised), U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, p. 84, 141
- Geschwind, C. (2001). California Earthquakes: Science, Risk, and the Politics of Hazard Mitigation. Johns Hopkins University Press. pp. 119–122. ISBN 978-0801865961.
- Yule, D.; Sieh, K. (2003). "Complexities of the San Andreas fault near San Gorgonio Pass: Implications for large earthquakes". Journal of Geophysical Research (American Geophysical Union) 108 (B11).
- Yeats, R. (2012), Active Faults of the World, Cambridge University Press, pp. 100, 101, ISBN 978-0-521-19085-5
- "Quake shakes southland; Desert towns hardest hit". Los Angeles Times. December 5, 1948.
- Desert Hot Springs Earthquake – Southern California Earthquake Data Center