calaveras fault earthquake

The largest earthquake within 30 miles of Calaveras County, CA was a 3.3 Magnitude in 2017. The earthquake faults in California, including the Hayward, the Calaveras and the San Andreas faults. In other words, we don’t know for certain if this northern section of the Calaveras Fault is due for another big quake in the near future. Witter, R. C., Kelson, K. I., Barron, A. D., & Sundermann, S. T. (2003). This article has been updated to reflect recent earthquakes in the swarm. These shallow repeaters align well … The north-northwest trending Calaveras Fault makes a westward bend or stepover under the northern end of the reservoir, crossing from the east bank of the reservoir south of the dam to the west side of Observation Hill which forms the left (west) abutment of the dam, according to a technical report on the Calaveras Fault. Two minutes after 9 a.m., a third earthquake hit, registering a magnitude of 3.3 at a depth 4.3 km. 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. Credit: SFPUC. Doubtfire.” The quakes are occurring at a depth of 5-7 km (3-4 mi) on a heretofore unmapped fault or set of faults, and exhibit a diversity of mechanisms, some similar to the ‘right-lateral’ (whichever side you are on, the other side moves to the right) Calaveras Fault, and others perhaps related to the ‘blind thrust fault’ that has jacked up Mount Diablo. This means having an emergency kit and plan, securing your contents, retrofitting an older home, and considering insurance. The U.S. Geological Survey (USGS) publishes updated frequency and severity likelihood every six years for the entire U.S. Over 70 quakes have struck in the area around the Calaveras Dam since mid-August. The north-northwest trending Calaveras Fault makes a westward bend or stepover under the northern end of the reservoir, crossing from the east bank of the reservoir south of the dam to the west side of Observation Hill which forms the left (west) abutment of the dam, according to a technical report on the Calaveras Fault. 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. The initial earthquake The San Andreas fault system is to the west, the Garlock fault is to the south and the faults of the Sierra Nevada are to the east. Holocene slip rate and earthquake recurrence of the northern Calaveras fault at Leyden Creek, northern California. He noted that there have been several large earthquakes linked to construction of dams and reservoirs in India and Egypt. It produced the October 30, 2007 … It's a kind of "Faults For Dummies!" The largest historical quake on the Calaveras Fault was a M=6.6 event in 1911 (Doser, 2009), but far too … The largest historical quake on the Calaveras Fault was a M6.6 earthquake in 1911. 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. The Calaveras Fault, like the San Andreas Fault to the west, is a right-lateral strike-slip fault that is part of the San Andreas Fault System in the San Francisco Bay region. Some scientists predict that the Bay Area's the next major quake will occur on this fault. 178, pg. “Swarms may indicate other activity in the area,” said Burgmann. Earthquake Information for Calaveras County, California. During excavation of Observation Hill, faults that had never before been mapped as … Construction on the new Calaveras Dam was completed last year. Earthquake swarms usually end without a major event and generally die out within days to months. Nevertheless, should this swarm penetrate the Calaveras Fault, the chances of a larger shock will climb, and the monitoring vigilance will intensify. Fault connectivity defines the maximum earthquake rupture length, and the three-dimensional (3D) geometry of faults affects the dynamics of fault rupture, slip, and ground motion (11–15). However, the rms residuals for P-wave arrivals at many of the network stations were as high as 0.25 sec due to the laterally heterogeneous structure of this area which deviates from the … Monitoring Velocity Variations in the Crust Using Earthquake Doublets: An Application to the Calaveras Fault, California July 1984 Journal of Geophysical Research Atmospheres 89:5719-5731 The Hayward Fault splinters from the Calaveras Fault, which itself is an offshoot of the In California, the plate is sliding northwestward along a transform boundary, the San Andreas Fault, toward the subduction zone. Shaking can begin suddenly but have lasting impacts. 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). The Hayward Fault runs from San Pablo Bay to Fremont. It is unclear on which faults these quakes are occurring, but this activity is a sign that the area is anything but quiet. This earthquake and its aftershocks took place within a very dense seismic network. The Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. A magnitude-1.9 tremor on October 8 was the latest in a series of small earthquakes near Northern California’s Calaveras Dam, located about 38 miles (61 kilometers) southeast of San Francisco. Along some active faults, deformation and offset occur continuously even in the absence of large earthquakes; this is referred to as fault creep which generally proceeds at rates of millimeters to tens of millimeters per year. Earthquake scientists are far more worried about the potential violence of a more northern stretch of the Calaveras Fault, between the towns of Danville and San Ramon. Lian Xue, Roland Bürgmann , David R. Shelly, Christopher W. Johnson, Taka’aki Taira (2018), Kinematics of the 2015 San Ramon, California earthquake swarm: Implications for fault zone structure and driving mechanisms, in press, Earth and Planetary Science Letters. It is one of the fastest creeping fault segments in the San Francisco Bay Region. The slip rate along the fault … 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. Only one 1911 seismogram from the U.S. survived, from the University of St. Louis, which was saved by Prof. John Ebel, former director of the Weston Observatory of Boston College. The 2 to 8mm/yr range of creep rates along the HF is well documented by over 30 alignment arrays (AAs) and 5 creepmeters covering … The Calaveras Fault: It is possible to walk down Locust Street from Vista Hill Park and walk through the neighborhood to examine the structural damage to streets, curbs, walls, and buildings that are slowly being deformed, warped, or broken by the slow creeping motion of the Calaveras Fault. At that time, most U.S. seismic observatories were run by scientist priests at Jesuit universities. The new dam was designed to withstand a magnitude-7.25 earthquake. It is also being subducted far to the northwest into the Aleutian Trench. We use specialized high … 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. “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. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal). The white lines indicate faults recognized by the USGS. USSD Dams and Levees Bulletin of the United States Society on Dams Summer 2019 Issue No. The 2003 Working Group Report divided the fault into three segments. 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. Soc. The fault cuts through the towns of Walnut Creek, San Ramon, Dublin, Pleasanton, Sunol, and Hollister. “I think the swarm is just a good reminder of seismic hazard that exists along the fault.”. Kelson, K. I., Simpson, G. D., Lettis, W. R., & Haraden, C. C. (1996). Calaveras County, CA has a moderate earthquake risk, with a total of 1 earthquakes since 1931. 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. At that time, most U.S. seismic observatories were run by scientist priests at Jesuit universities. Hayward-Calaveras fault zone (HCFZ), characterization of the creep rates along the faults with a high spatial resolution is necessary. [4] The geometry of fault zones within the Earth is revealed primarily by seismicity. A 3.6-magnitude earthquake was reported Wednesday morning east of San Jose, according to the U.S. Geological Survey. 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. Credit: Rick Harlan (used with permission of SFPUC). 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. The white lines … California Geological Survey The HCFZ considered here encompasses the HF, the northern CF, and the central CF from the junction with the northern CF to Gilroy (Figure 1). Another swarm struck the central portion of the Calaveras Fault in April 2016 (http://temblor.net/earthquake-insights/calaveras-535/); neither triggered a larger shock. They came one after the other along the Calaveras Fault in Santa Clara County. Although the area has seen little significant seismic activity over the past 100 years, paleoseismic studies at Leyden Creek about one mile (2 kilometers) north of the dam indicate that this section of the northern Calaveras fault has generated a number of ground rupturing earthquakes of possibly up to around magnitude-7.0 over the last 2,500 years (Kelson et al. We suggest that Zone V fails only … future moderate earthquakes on the Calaveras Fault. 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. UC Berkeley seismologists have proven that the Hayward Fault is essentially a branch of the Calaveras Fault that runs east of San Jose, which means that both could rupture together, resulting in a significantly more destructive earthquake than previously thought. This is a relief to the 27 million residents who rely on the Calaveras Reservoir. 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