USGS A magnitude 3.7 earthquake was followed by a 3.6 within one minute near Morgan Hill, Calif. on … 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 … 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. 's (1990) Zone V “stuck patch” on the central Calaveras fault, providing new support for their model of Calaveras fault earthquake activity. 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 San Ramon segment (Figure 1) is the dominant … This section is 43 km of a total fault length of 156 km. The surface trace is offset by several kilometers from the deep portion of the fault 3-5 km below ground (blue line). 0000003006 00000 n In 1979, the 5.7M Coyote Lake Earthquake ruptured to the south of the 1984 and 1911 earthquakes. In the Bay area there are three major faults, from West to East the San Andreas, the Hayward, and the Calaveras; all are part of the San Andreas fault system. 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. The fault cuts through the towns of Walnut Creek, San Ramon, Dublin, Pleasanton, Sunol, and Hollister. The epicenter was along the Calavaras Fault and 9 … Simpson and others (1999 #5528) reported faulted late Holocene deposits at Welch Creek. 0 The Calaveras and Hayward faults are major components of the San Andreas fault system in the San Francisco Bay region. The Calaveras fault, part of the San Andreas fault system, is one of the most seismically active faults in central California. September 28, 2001. These faulted deposits range in age from pre-Holocene to modern. San Diego. This fault and its southern continu- ation, the Paicines fault, are part of right-slip fault zones that branch northeastward from the … The reservoir sits atop a major branch of the San Andreas Fault system called the Calaveras Fault. The quakes were all centered along the Calaveras fault system, which is located in the hills east of the San Francisco Bay Area. 68 0 obj <> endobj According to the USGS, the quake was widely felt by dozens of people in Fremont, Milpitas and San Jose. <]>> 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 … 0000000576 00000 n %%EOF 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. 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). The northern extent of the fault zone is somewhat conjectural. The quake happened at a depth of around 4 miles (6.5 km) on the infamous San Andreas Fault, close to a region where the Calaveras Fault branches off. 125–850 yr (average recurrence for past 5 k.y.). Below is a list of creepmeters, from North to South, located on the San Andreas, … Major dextral strike-slip fault zone of the larger San Andreas fault system. The Calaveras fault produced the M6.2 Morgan Hill Earthquake in 1984. 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. (Here is a regional map courtesy of Xerox PARC.) Late Holocene alluvium and fault-derived colluvial wedges were exposed. A study by Kelson and others (1996 #5284). Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismic creep. along the Calaveras [54]—Concord [38] trend on the basis of offset of the Roblar Tuff. The Calaveras Fault. The Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. Here the estimated deep slip rates drop from 15 to 6 mm/yr on the Calaveras fault… Based on present creep rates, the fault can be divided into two overall segments; that south of the Calaveras Reservoir, and the San Ramon segment (Kelson, et al, 1992), between Sunol and Danville. Welch Creek (site 54-4). !Z_�q��C�C���"�V�t_��p���+��X��]�̧�Y%�L J�*3��f�,�%� IW�d���N���m �l@��R�Hq�e������@����@��y�z��>�o�uU� �քq�[Ӥ���^���2p��L �=z 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 fault extends northward through the Diablo Range for about 90 miles to the vicinity of Danville. Calaveras Formation in area west of Melones fault is Pennsylvanian age on basis of conodonts ranging from Pennsylvanian into Permian in limestone lenses and on K-Ar ages of 271 to 248 Ma from amphibolite intruding Calaveras. The complete fault zone, including the Rodgers Creek fault, is divided by seismologists into three segments – Rodgers Creek, Northern Hayward, and Southern Hayward. [1] 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 ML5.5 earthquake. Sarna-Wojcicki (1992 #5265) reported about 13±7 km of cumulative dextral offset in the past 6 m.y. 0000006320 00000 n 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. 0000001941 00000 n 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. Digging a paleoseismic trench at Tule Pond on the Hayward fault. Relocated events on the Hayward and Calaveras faults in particular, have been especially revealing and suggest that at seismogenic depth the Hayward fault is the major northward extension of the Central Calaveras fault (Manaker, Michaels, and Burgmann, 2003), rather than the Northern Calaveras fault. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismic creep. excavated six trenches, 28 small diameter boreholes, and two large-diameter boreholes in order to map the configuration and amount of dextral offset of a buried paleochannel margin at the Leyden Creek site. The Calaveras Fault splays away from the San Andreas Fault about 10 miles south of Hollister near the town of Paicines, California. 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. 0000000866 00000 n According to the USGS, there are seven "significant" faults in the Bay Area: the San Andreas Fault… 0000002685 00000 n All three quakes were on the Calaveras fault system that weaves its way through the East Bay hills. 0000001075 00000 n 0000002930 00000 n Page (1982 #5521) estimated that cumulative late Cenozoic dextral offset is about 20±4 km. 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 initial earthquake, which occurred at a depth of 3.5 miles, was 3 miles away from San Jose and 8 miles from Gilroy. The U.S. Tsunami Warning System said there was no tsunami threat. 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 Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. 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 The aftershock had a depth of 3.2 miles. The surface trace is offset by several … Within a minute, it was followed by a magnitude 3.6 quake along the Calaveras Fault in Santa Clara County. Of casualties or damage most up-to-date information, please refer to the vicinity Danville. 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