Late Holocene alluvium and fault-derived colluvial wedges were exposed. The San Ramon segment (Figure 1) is the dominant … Digging a paleoseismic trench at Tule Pond on the Hayward fault. So it's probably worth knowing where the major fault lines in the Bay Area are. Within a minute, it was followed by a magnitude 3.6 quake along the Calaveras Fault in Santa Clara County. The Calaveras Fault and lost seismograms 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. A magnitude 3.1 quake rattled Concord on Thursday afternoon.USGSA magnitude 3.1 quake rattled Concord on Thursday afternoon.The United States Geological Survey detected the quake at 4:48 p.m. with an epicenter 0.7 miles from Concord, 2.4 miles from Pleasant Hill and 15 miles from Berkeley. 0000002930 00000 n trailer Simpson and others (1999 #5528) reported faulted late Holocene deposits at Welch Creek. Preliminary map showing known and suspected active faults in … These faulted deposits range in age from pre-Holocene to modern. (for section) versus N31°W (for whole fault). The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. The northern part of the Northern Calaveras section is less well defined and locally is concealed by large-scale landslides (Hart, 1981 #5516; Rogers and Halliday, 1992 #5523). Dextral slip is presumed to transfer from the Calaveras fault to the Hayward fault in the Mission Hills region, an area of uplift in the contractional stepover between the two faults. 's (1990) Zone V “stuck patch” on the central Calaveras fault, providing new support for their model of Calaveras fault earthquake activity. The red line is the newly discovered surface trace connecting the southern end of the Hayward Fault to the Calaveras Fault, once thought to be an independent system. %%EOF #5501 Armstrong, C.F., 1979, Coyote Lake earthquake of 6 August 1979: California Geology, v. 32, no. Alternatively, the slip may continue northward along reverse and dextral-reverse faults in the East Bay Hills (Page, 1982 #5521). Here the estimated deep slip rates drop from 15 to 6 mm/yr on the Calaveras fault… Simpson and others (1999 #5528) excavated a total of nine trenches (three fault normal and six fault parallel) across traces of the northern Calaveras fault at Welch Creek in order to assess the slip rate and earthquake history of the northern section of the Calaveras fault. The Calaveras Fault. The red line is the newly discovered surface trace connecting the southern end of the Hayward Fault to the Calaveras Fault, once thought to be an independent system. The tremor hit at 3:44 a.m. with a depth of of 5.6 miles near Alum Rock, according to the U.S. Geological Survey. The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. U.S. Army exploration party lead by John C. Fremont passed through the area in 1847 and had a nearly disastrous encounter with troops under the Commandante General of the Mexican … The Hayward Fault is one of the secondary faults in this diffuse zone, along with the Calaveras Fault to the east and the San Gregorio Fault, west of the San Andreas. 0000006320 00000 n The Calaveras fault system stretches 131 km, from south of Hollister, northward, into the Danville-Walnut Creek area (Taylor, 1992). %PDF-1.4 %���� According to the USGS, there are seven "significant" faults in the Bay Area: the San Andreas Fault… The surface trace is offset by several kilometers from the deep portion of the fault 3-5 km below ground (blue line). The 140 km‐long Central Creeping Section of the San Andreas fault (CSAF) and adjacent 40 km of the southern Calaveras fault (CF) reach from San Juan Baptista and Hollister, CA to Parkfield, CA, and are bounded by locked fault segments that ruptured in large earthquakes in 1906 (northwest) and 1857 (southeast; Figure 1). 0000001075 00000 n The red line is the newly discovered surface trace connecting the southern end of the Hayward Fault to the Calaveras Fault, once thought to be an independent system. The Calaveras and Hayward faults are major components of the San Andreas fault system in the San Francisco Bay region. 0000001941 00000 n 0000000866 00000 n In 1979, the 5.7M Coyote Lake Earthquake ruptured to the south of the 1984 and 1911 earthquakes. USGS A magnitude 3.7 earthquake was followed by a 3.6 within one minute near Morgan Hill, Calif. on … Map of the Calaveras Fault zone in Hollister, California (Google satellite view with US Geological Survey fault mapping data—red is aseismic creeping section, orange is older earthquake fault traces). The Calaveras Fault splays away from the San Andreas Fault about 10 miles south of Hollister near the town of Paicines, California. 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. The surface trace is offset by … The northern extent of the fault zone is somewhat conjectural. 54a Last Review Date: 1999-03-04 Slip rates were calculated by mapping and measuring the offset of a terrace back-edge and by constructing isopach contours of an offset buried debris flow. H��W�r�H��+jND�0�e�$��-�#��s��P"�$,`�d������3^�Z�r�̗Y/��Df7,�W���Ul"��.�؄��O�iT�Y}[�f���5�. 0000008989 00000 n The U.S. Tsunami Warning System said there was no tsunami threat. The Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. Below is a list of creepmeters, from North to South, located on the San Andreas, … Leyden Creek (site 54-2). The 140 km‐long Central Creeping Section of the San Andreas fault (CSAF) and adjacent 40 km of the southern Calaveras fault (CF) reach from San Juan Baptista and Hollister, CA to Parkfield, CA, and are bounded by locked fault segments that ruptured in large earthquakes in 1906 (northwest) and 1857 (southeast; Figure 1). The epicenter was along the Calavaras Fault and 9 … 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 … September 28, 2001. The reservoir sits atop a major branch of the San Andreas Fault system called the Calaveras Fault. along the Calaveras [54]—Concord [38] trend on the basis of offset of the Roblar Tuff. This fault and its southern continu- ation, the Paicines fault, are part of right-slip fault zones that branch northeastward from the … The U.S. Geological Survey said that the first quake struck at 3:54 p.m. local time at a depth of 3.3 miles, less than six miles northeast of Milpitas along the Calaveras Reservoir. <]>> 70 0 obj<>stream On September 28, 2001, paleoseismologists from the U.S. Geological Survey opened a trench on the southern Hayward fault at a site called Tule Pond, also known as Tyson's Lagoon, just south of the Fremont BART (Bay Area Rapid Transit) station in Fremont, California. One theory is that the fault zone transfers slip to the Concord fault zone [38] in a right-releasing step-over (Oppenheimer and MacGregor-Scott, 1992 #5520; Working Group on Northern California Earthquake Probabilities, 1996 #1216). The United States Geological Survey detected the quake at 4:48 p.m. with an epicenter 0.7 miles from Concord, 2.4 miles from Pleasant Hill and 15 miles from Berkeley. The Calaveras fault zone is located in the eastern San Francisco Bay region and generally trends along the eastern side of the East Bay Hills, bounds the western side of San Ramon Valley, extends into the western Diablo Range, bounds the eastern side of Santa Clara Valley, extends into Hollister Valley, and eventually joins the San Andreas fault zone [1] along the eastern part of the Gabilan Range. x�b```f``����� �� Ȁ �@1�hPRPb2:�ɠ? Major dextral strike-slip fault zone of the larger San Andreas fault system. The aftershock had a depth of 3.2 miles. N26°W The Northern Calaveras section generally is marked by geomorphic features characteristic of Holocene dextral strike-slip offset, such as dextrally deflected and offset drainages, linear troughs, linear scarps on alluvium, side-hill benches, beheaded drainages, and closed depressions (Herd, 1977 #5484; 1978 #5485; Bryant, 1981 #5504; Hart, 1981 #5516). (Here is a regional map courtesy of Xerox PARC.) The complete fault zone, including the Rodgers Creek fault, is divided by seismologists into three segments – Rodgers Creek, Northern Hayward, and Southern Hayward. 0000002446 00000 n Such an earthquake could unexpectedly change people’s lives and impact the Bay Area’s infrastructure and economy, but updated building codes and … The Calaveras fault, part of the San Andreas fault system, is one of the most seismically active faults in central California. 0000002685 00000 n The Calaveras Fault is part of the greater San Andreas Fault System in the San Francisco Bay region. endstream endobj 69 0 obj<> endobj 71 0 obj<> endobj 72 0 obj<>/Font<>/XObject<>/ProcSet[/PDF/Text/ImageC]/ExtGState<>>> endobj 73 0 obj<> endobj 74 0 obj<> endobj 75 0 obj[/ICCBased 80 0 R] endobj 76 0 obj<> endobj 77 0 obj<> endobj 78 0 obj<> endobj 79 0 obj<>stream 0000001226 00000 n Calaveras fault zone, Northern Calaveras section (Class A) No. 68 14 The initial earthquake, which occurred at a depth of 3.5 miles, was 3 miles away from San Jose and 8 miles from Gilroy. 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