Our ability to resolve fault zone structure and hence to address many essential aspects of earthquake behavior, is limited by our ability to obtain precise earthquake locations. It's a kind of "Faults For Dummies!" Within a minute, it was followed by a magnitude 3.6 quake along the Calaveras Fault in Santa Clara County. More than 35 quakes ranging as high as a magnitude-3.5 have been recorded by the U.S. Geological Survey since September 27. The largest historical quake on the Calaveras Fault was a M=6.6 event in 1911 (Doser, 2009), but far too … The Calaveras reservoir provides drinking water storage for residents throughout California, according to the San Francisco Public Utilities Commission (SFPUC), who manages the reservoir. The Calaveras and Hayward faults extend up the east side of the San Francisco Bay. The first quake was reported at 6:58 a.m. USGS The similarity of seismograms recorded by two seismic stations demonstrate that the 31 October 2007 moment magnitude M5.4 Alum Rock earthquake is a repeat of a 1955 M L 5.5 earthquake. Earthquake swarms usually end without a major event and generally die out within days to months. It’s the latest quake in an ongoing swarm that started ramping up on August 17, 2020. But by the time these professors began to die in mid-century, their lifelong seismogram archives were thrown out. future moderate earthquakes on the Calaveras Fault. We suggest that Zone V fails only … This system forms the plate tectonic boundary between the North American Plate and the Pacific Plate. It passes through parts of Berkeley, Oakland, Hayward and Fremont before branching into a set of surface faults that connect it to the central part of the Calaveras Fault, according to the USGS. Credit: SFPUC. The SFPUC’s Completion Fact Sheet for the recently completed Calaveras Dam Replacement Project (CDRP) indicates that the fault runs only about 1,000 feet (300 meters) from the new dam (SFPUC, 2019). Repeating earthquakes can be grouped in three categories: 1) small cumulative slip and medium depths (3-7 km), characteristic of the northern Hayward fault; 2) large cumulative slip and medium to large depths (3-11 km), characteristic of the Calaveras fault; and shallow events (less than 3 km), occurring only at the junction between the Hayward and Calaveras faults. This earthquake and its aftershocks took place within a very dense seismic network. “After the landslides were removed, we found additional, smaller faults that had not been recognized during the original design studies for the new dam” said Rick Harlan, an engineering geologist who worked for the SFPUC’s construction management team during the dam replacement project. The initial earthquake As far as dam safety, the SFPUC confirmed that there were “no impacts at all to the dam or its surrounding facilities” following any earthquakes in this swarm. The San Andreas fault system is the … Those studies indicate timing of the most recent large earthquake is poorly constrained but suggest an average interval between surface rupturing earthquakes of 250 to 850 years, highlighting the uncertainty in what seismologists call the “recurrence interval” of major earthquakes. Nevertheless, should this swarm penetrate the Calaveras Fault, the chances of a larger shock will climb, and the monitoring vigilance will intensify. At the same time, the North American Plateis moving southwestward relative to the Earth's core, but southeastward relative to the Pacific Plate, due to the latter's much faste… Shaking can begin suddenly but have lasting impacts. While … Kelson, K. I., & Sundermann, S. T. (2007). There are several reasons why these earthquakes may be occurring here. Both occurred on Oppenheimer et al. The reservoir is located less than 20 miles from where Tesla is based in Fremont, California, and sits on the Calaveras fault system. The Calaveras fault system runs over 80 miles, from south of Hollister into the Danville-Walnut Creek area. The first was a 4.0 magnitude earthquake about six miles northeast of San Martin around 6:48 a.m., according to USGS, and another shortly after east of Morgan Hill. Credit: Dicklyon (CC BY-SA 4.0). Studies conducted in the late 1990s indicated that the original dam, which was built in 1919, didn’t meet seismic safety standards given its construction and proximity to the nearby Calaveras Fault. A 3.6-magnitude earthquake was reported Wednesday morning east of San Jose, according to the U.S. Geological Survey. He noted that there have been several large earthquakes linked to construction of dams and reservoirs in India and Egypt. The largest historical quake on the Calaveras Fault was a M=6.6 event in 1911 (Doser, 2009), but far too little is known about this large event. ... Like all of California, the Central Valley—which is ringed by faults—is earthquake country. But by the time these professors began to die in mid-century, their lifelong seismogram archives were—inconceivably and unconscionably—thrown out. That is enough to fill Levi’s Stadium from bottom to top four times, according to SFPUC. A series of small earthquakes near the recently built Calaveras Dam replacement is a reminder of the significant seismic hazard at the new dam site. They came one after the other along the Calaveras Fault in Santa Clara County. The northern segment of the Calaveras Fault is virtually locked and this segment of the fault creeps at a rate between 2 and 3 mm/yr. It is also being subducted far to the northwest into the Aleutian Trench. Because of this, “the static stress change at depth must have been minimal.” This suggests that excavation during dam construction is not likely to be the cause of this swarm. The quakes were all centered along the Calaveras fault system, which is located in the hills east of the San Francisco Bay Area. In this study, we greatly improve the earthquake locations on the Calaveras Fault. If you live or work in the East Bay, this is the time to ask yourself if you are quake ready. The Calaveras fault here is unusual because it creeps, moving a few millimeters per year, instead of storing up energy and releasing it all in a big earthquake. The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. Kelson, K. I., Simpson, G. D., Lettis, W. R., & Haraden, C. C. (1996). The largest earthquake within 30 miles of Calaveras County, CA was a 3.3 Magnitude in 2017. Earthquake Information for Calaveras County, California. When full, it can store 96,850 acre-feet, or 31 billion gallons of water. It is one of the fastest creeping fault segments in the San Francisco Bay Region. Hayward-Calaveras fault zone (HCFZ), characterization of the creep rates along the faults with a high spatial resolution is necessary. Geodetic monitoring of the Calaveras fault near this location indicates about 6 mm/yr (0.24 inches/year), but further south near Hollister the … Details of the 3D fault geometry at stepovers and bends—particularly in urban settings—are often lacking, limiting efforts to constrain hazard calculations in these areas. Two 3.4 magnitude earthquakes struck hours apart in the same area in Northern California on Sunday, according to officials. Calaveras County, CA has a moderate earthquake risk, with a total of 1 earthquakes since 1931. Digital compilation of Northern Calaveras Fault data for the Northern California map database: collaborative research with William Lettis & Associates, Inc., and the US Geological Survey. But “they always cause discussion and debate,” said Burgmann. Swarms likely light up portions of faults that suddenly begin to creep—or slip at a much higher rate than usual. With a slip rate of about 15 mm/yr (0.6 in/yr) and a length of about 100 km (60 mi), the Calaveras is highly active and certainly capable of a M7+ earthquake. Doser, Diane I., Kim B. Olsen, Fred F. Pollitz, Ross S. Stein, and Shinji Toda (2009), The 1911 M∼6.6 Calaveras earthquake: Source parameters and the role of static, viscoelastic, and dynamic Coulomb stress changes imparted by the 1906 San Francisco earthquake, Bull.Seismol. Journal of Geophysical Research: Solid Earth, 101(B3), 5961-5975. The fault cuts through the towns of Walnut Creek, San Ramon, Dublin, Pleasanton, Sunol, and Hollister. 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