THE LIVERMORE EARTHQUAKE* OF JANUARY 1980
CONTRA COSTA AND ALAMEDA COUNTIES, CALIFORNIA
All photos by T. L. Bedrossian unless otherwise noted.
* These earthquakes also have been referred to as the Greenville earthquakes and the Mount Diablo earthquakes.
The following article summarizes information collected by the authors and other CDMG staff shortly after the Livermore earthquakes of January 24 and January 26, 1980. The observations presented here are preliminary and may be modified by more detailed studies .......Editor.
At 11:00 a.m. PST on Thursday, January 24, 1980, an earthquake of Richter Magnitude 5.5 (M 5.5) shook the San Francisco Bay area. The epicenter of the quake was located approximately 12 kilometers southeast of Mount Diablo, in the sparsely-populated hills north of Livermore Valley (figure 1). According to Bolt and others (1980), the M 5.5 earthquake was followed within two minutes by after-shocks of M 5.2 and M 4.2. This close repetition of M > 4 events resulted in a relatively long duration of shaking felt by people in the Livermore Valley and surrounding hills. Based on different methods of computation, the focal depth of the M 5.5 event earthquake was reported to be 11.8 kilometers (University of California Seismograph Station at Berkeley) and 6.5 kilometers (U. S. Geological Survey at Menlo Park). Discontinuous surface rupture associated with the earthquake was located approximately 12 kilometers south of the epicenter where a trace of the Greenville fault, previously mapped by Rogers (1966), crosses Vasco Road (figure 1; photo 1).
SEE FIGURE 1
Figure 1. Location of principal faults, fault rupture, earthquake epicenters, and CDMG portable seismographs and strong motion-instruments in the Livermore area. Faults and zone of fault rupture plotted by E. W. Hart; epicenter, seismograph station, and strong-motion instrument locations plotted by J. G. Moreno.
On January 26, 1980, at 6:33 p.m. PST, a second earthquake jolted the Livermore Valley and surrounding area. The epicenter of the second quake was located in the vicinity of Frick Lake, 14 kilometers south of the first earthquake epicenter and approximately 10 kilometers northeast of the town of Livermore (figure 1). Seismologists from the University of California, Berkeley, reported a M 5.8 and a focal depth of 14.5 kilometers while the U. S. Geological Survey at Menlo Park reported a M 5.2 and a focal depth of 9 kilometers. New zones of surface rupture were observed south of Vasco Road (photo 2) and across Laughlin Road (photos 3, 4) along a projected trace of the Greenville fault previously mapped by Huey (1948) and Herd (1977).
Damage from the earthquakes was most evident in Livermore, the largest city close to the epicenters. After the January 24 event, 10,000 people were inconvenienced by loss of power for more than two hours. Plate glass windows shattered and piles of merchandise were scattered in shop aisles. Many mobile homes at the Sunrise Mobile Home Park were knocked off their foundations (photo 5), buildings swayed and cracked in numerous places (photo 6), and gas lines snapped. The overpass along Interstate 580 at Greenville Road was closed when paving on the east side of the structure settled nearly 30 centimeters as a result of shaking in fill materials. Although the overpass did not break, traffic was diverted until repairs and resurfacing of the road were completed. Fortunately, only a few minor injuries and one death (possibly from a heart attack) were reported as a result of the quake.
SEE PHOTO 1
Photo 1. Left-stepping zone of cracks across Vasco Road. Right-lateral offset of the centerline at this location measured 1.5 to 2.0 centimeters.
SEE PHOTO 2
Photo 2. Left-stepping cracks in soil south of Vasco Road. The cracks are located along a trace of the Greenville fault previously mapped by Rogers (1966).
SEE PHOTO 3
Photo 3. Left-stepping cracks across Laughlin Road just northwest of Frick Lake. These cracks developed sometime after 2:30 p.m. January 24. These en echelon cracks showed 5 to 10 millimeters of right-lateral offset and could be traced for a distance of about 300 meters northwestward along a projected trace of the Greenville fault mapped by Huey (1948) and Herd (1977). White lines across the cracks were painted by Woodward-Clyde Consultants to monitor subsequent movement along the fault.
SEE PHOTO 4
Photo 4. Large crack in Laughlin Road along projected trace of Greenville fault previously mapped by Herd (1977). Between January 25 and 27, 1980, this crack displayed 1 to 2 millimeters of right-lateral movement.
SEE PHOTO 5
Photo 5. Damage to mobile home in Sunset Mobile Home Park, Livermore. Photo by Donn Ristau.
SEE PHOTO 6
Photo 6. Offset chimney in house along Laughlin Road in the vicinity of the epicentral area of the January 26 earthquake.
Probably of most concern to residents of Livermore were reports of damage to the nuclear research center at Lawrence Livermore Laboratory. Damage to the facility is estimated to approach $10 million. However, most of the damage was non-structural, consisting largely of broken PVC pipes, paneling, glassware, overturned book shelves and untied trailers. Buildings housing radioactive materials and a reactor were unharmed. Costly damage was also experienced at the Wente Bros. Livermore winery where over a dozen giant stainless steel tanks were overturned by earthquake shaking and 168 out of 208 wine tanks suffered collapse or failure to some degree.
Since 1850, no earthquakes as large as those of January 24 and 26, 1980, are known to have occurred on the eastern side of Livermore Valley. However, there have been a number of smaller earthquakes in this area of less than M 5. The Earthquake Epicenter Map of California (Real and others, 1978) shows the epicenters of three events M 4.0 to M 4.9 which occurred east of Livermore between 1900 and 1974. The most recent earthquake of this size was M 4.7 event on June 21, 1977 (Toppozada and others, 1979).
The Greenville-Mount Diablo fault, which produced the Livermore Valley earthquakes, is one of a number of active faults along the east side of the Coast Ranges. Lying to the east of the major cities of the San Francisco Bay area, these faults have not gained the same notoriety as the San Andreas, Hayward, or Calaveras faults. Since the great San Francisco earthquake of 1906, there have not been any earthquakes on the eastern Coast Range faults greater than M 5. However, prior to 1906 there were six earthquakes as large or larger than the Livermore Valley earthquakes (figure 2).
SEE FIGURE 2
Figure 2. Location of historic earthquakes near the Livermore Valley. Compiled by S. P. Bezore.
Of these earthquakes, the nearest to Livermore was the Antioch earthquake of May 19, 1889. Newspaper accounts at that time indicate that the area of greatest damage included the communities of Antioch, Clayton, and Collinsville where glassware and crockery were shaken from shelves and chimneys were toppled. The epicenter was most likely on the Antioch fault or on the northern end of Greenville-Mount Diablo fault.
On May 19, 1902, an earthquake of M 5.5 occurred near Elmira, Solano County. Chimneys were knocked down in Elmira and minor damage occurred in Vacaville and Fairfield.
One of the largest earthquakes known to have struck the San Francisco Bay area occurred on April 19, 1892 in the Vacaville-Winters area. Only the 1906 San Francisco earthquake was larger. This M 6.8 earthquake caused extensive damage to Vacaville, Winters, and Dixon. Like the Livermore Valley earthquake, it was followed 2 days later by another large event, a M 6.3 earthquake on April 21, 1892. Causative faults have not been identified for either the 1902 Elmira earthquake or the 1892 Vacaville-Winters earthquakes.
In the region southeast of Livermore, near the edge of the San Joaquin Valley, two earthquakes are known to have occurred --- a M 6 earthquake on April 10, 1881 and a M 5.7 earthquake on July 14, 1866. Centered in a sparsely populated area, no serious damage was reported in newspaper accounts of either earthquake.
With eight earthquakes of M 5.5 or greater occurring in a 114-year period from 1866 to 1980, the east side of the Coast Ranges represents one of the more active seismic zones in California. No evidence exists that an earthquake the size of the 1906 San Francisco earthquake could occur in this area, but the historical record indicates that locally destructive earthquakes are likely to occur.
On January 24, two teams of CDMG geologists were dispatched from the San Francisco District Office to investigate surface displacement resulting from the earthquake, to identify any associated land instability or geologic hazards, and to gather data for fault evaluation relative to the CDMG Alquist-Priolo Special Studies Zones program. Follow-up investigations were conducted through February 7, 1980, and will continue periodically throughout the coming year as part of the Alquist-Priolo Special Studies Zones fault evaluation program.
SEE FIGURE 3
Figure 3. Location of aftershocks recorded on January 28 and 29 following installation of CDMG seismographs on January 27, 1980. Compiled by CDMG seismology group.
Also on January 24, two teams of technicians from the CDMG Strong Motion Instrumentation Program were sent to the Livermore area. One team was directed to recover response records from recording instruments in the area, while the other team placed three additional instruments near the epicentral area to collect data on aftershocks (figure 1).
Seismologists from CDMG did not initiate a monitoring program following the M 5.5 earthquake of January 24 because instrumentation of the aftershock zone seemed to be adequate. However, the second earthquake of January 26, which occurred outside of the established aftershock arrays, prompted the CDMG seismology group to deploy 10 temporary seismograph stations (figures 1 and 3).
Results of the CDMG response efforts are summarized below.
Ground Rupture Studies
Discontinuous surface rupture due to faulting was observed along the Greenville fault zone, approximately 12 kilometers south of the January 24 earthquake epicenter (figure 1). Within 4 hours of the January 24 event, CDMG geologists responding to the earthquake located two sets of cracks across Vasco Road, each showing up to 2 centimeters of right lateral offset (photo 1). Surface rupture on the northeast set of cracks was traced through soil (photo 2) approximately 2000 meters to the northwest and 300 meters to the southeast of Vasco Road. About 100 meters of additional rupture were observed southeast of Vasco Road following the January 26 event. Although the pattern of rupture was discontinuous, offset was predominantly right lateral with a vertical component measuring up to 13 centimeters. Variable vertical displacement (up either on the northeast or southwest), often associated with small graben features and extension normal to the fault strike, suggests that rupture along this segment of the fault was accompanied to some degree by downslope movement due to shaking.
Right lateral displacement was also observed northwest of Frick Lake on Laughlin Road (figure 1). Left stepping cracks (photo 3), showing 5 to 10 millimeters of right lateral offset, were traced northwestward through a field for a distance of about 300 meters. Another crack (photo 4) across Laughlin Road displayed 1 to 2 millimeters of additional right lateral movement following the January 26 earthquake. In addition, a discontinuous series of open cracks was observed for at least 300 meters across a dirt road and plowed field on the Rooney property west of Vasco Road (figure 1). No systematic vertical or horizontal displacement could be measured along this crack zone.
Numerous additional cracks were observed in paved roads along the general trend of the Greenville fault between Patterson Pass and Morgan Territory Roads. However, these cracks could not be conclusively attributed to fault rupture alone. Follow-up studies to determine the extent and nature of cracking will be made by CDMG as part of this year's Alquist-Priolo Special Studies Zones fault evaluation program. Although it is likely that parts of the Greenville fault will be zoned for special studies, the exact extent of zoning needs to be determined. Other faults in Livermore Valley also will be evaluated for possible zoning.
Strong Motion Studies
The CDMG Strong Motion Instrumentation Program is charged with the collection of statewide, detailed records of the responses of rock and soil units, and of man-made structures to strong motions generated by earthquakes. Data recorded on the accelerograph, an instrument that measures force-generating properties of seismic waves, provide information that can be used by engineers in designing earthquake-resistant structures.
To date, CDMG has established over 250 instrument stations throughout the state. In the San Francisco area, there are 27 stations deployed near the San Andreas fault, 8 near the Calaveras fault, and 10 near the Hayward fault (Davis, 1980). Of these stations, 21 provided strong motion records collected by CDMG following the January 24 and 26 earthquakes (table 1). Significant records of structural response from the January 24 event were collected from four structures and four foundation response instruments; five structures and two foundation response instruments provided significant records of structural response from the January 26 event. In addition, two of the three instruments deployed after the January 24 event provided excellent records of the January 26 event.
SEE TABLE 1
The CDMG seismology group initiated a field program following the January 26 earthquake. Equipment deployed consisted of Sprengnether MEQ-800 seismic recorders and Mark Product L-4C seismometers. Nine systems were operational on January 27 and the tenth station was operational on January 28. Station locations are shown in figure 1 and their coordinates tabulated in table 2. Figure 3 shows preliminary epicenter determinations for shocks for the days of January 28 and 29, 1980.
Table 2. Location of CDMG temporary seismograph stations installed after the January 26 event. See figure 1 for approximate map locations.
Because the earthquake of January 26 occurred outside of established aftershock arrays, the CDMG goal was to instrument the area in a manner that could contribute to aftershock studies of the earthquake of January 24, permit rapid separation of events occurring in the two epicentral areas, and allow investigations of shocks originating in the southern epicentral area. Instruments were collected and removed from the field on February 8, 1980. Preliminary processing of data has been limited to events of 30 seconds or greater total duration. So far, only a few aftershocks have been located in the southern epicentral area.
Other professional groups which responded with studies in the Livermore area include the University of California at Berkeley, the U. S. Geological Survey, Lawrence Livermore Laboratory, Earthquake Engineering Research Institute, California Department of Water Resources, CALTRANS, various departments of Alameda and Contra Costa Counties, and numerous geologic consulting firms. Post-earthquake investigations being conducted by various individuals from these groups include damage assessment, mapping of surface faulting, mapping of secondary effects, strong motion studies, aftershock studies, and earthquake intensity studies.
Bolt, B. A., McEvilly, T. V., and Uhrhammer, R. A., 1980, The Greenville earthquake sequence of January, 1980, California: Seismographic Station University of California, Berkeley, unpublished preliminary report of February 2, 1980, 14 p., 6 figs.
Davis, J. F., 1980, Activities in State government to mitigate earthquake hazards: California Division of Mines and Geology, unpublished paper presented at the Annual Meeting of the American Association for the Advancement of science, San Francisco, January 4, 20 p.
Herd, D. G., 1977, Geologic Map of the Las Positas, Greenville, and Verona faults, eastern Alameda County, California: U. S. Geological Survey, Open File Report 77-689, 25 p., scale 1:24,000.
Huey, A. S., 1948, Geology of the Tesla quadrangle, California: California Division of Mines, Bulletin 140, 75 p., scale 1:62,500.
Real, C. R., Toppozada, T. R., and Parke, D. L., 1978, Earthquake epicenter map of California: California Division of Mines and Geology, Map Sheet 39, scale 1:1,000,000.
Rogers, T. H., 1966, Geologic Map of California, San Jose sheet: California Division of Mines and Geology, scale 1:250,000.
Toppozada, T. R., Real, C. R., and Pierzinski, D. C., 1979, Seismicity of California, January 1975 through March 1979: California Geology, v. 32, no. 7, p. 139-142.