0000000866 00000 n All three quakes were on the Calaveras fault system that weaves its way through the East Bay hills. Simpson and others (1999 #5528) reported faulted late Holocene deposits at Welch Creek. [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. Both occurred on Oppenheimer et al. Welch Creek (site 54-4). The Calaveras fault system stretches 131 km, from south of Hollister, northward, into the Danville-Walnut Creek area (Taylor, 1992). Preliminary map showing known and suspected active faults in … 70 0 obj<>stream Hollister, California is located South of the San Francisco Bay area. 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 largest earthquake within 30 miles of Calaveras County, CA was a 3.3 Magnitude in 2017.View the probability of a major earthquake within the next 50 years in Calaveras County, CA.View the number of earthquake incidents in Calaveras County, CA by year that are more than 2.5 Magnitude. 0000001075 00000 n The northern extent of the fault zone is somewhat conjectural. 68 0 obj <> endobj 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 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. The Calaveras Fault. September 28, 2001. The quakes were all centered along the Calaveras fault system, which is located in the hills east of the San Francisco Bay Area. 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 last large event was the 1984 Morgan Hill event and the last moderate earthquake was the 2007 Alum Rock event. The white lines indicate faults recognized by the USGS. 0000000946 00000 n The complete fault zone, including the Rodgers Creek fault, is divided by seismologists into three segments – Rodgers Creek, Northern Hayward, and Southern Hayward. N26°W 's (1990) Zone V “stuck patch” on the central Calaveras fault, providing new support for their model of Calaveras fault earthquake activity. (Here is a regional map courtesy of Xerox PARC.) 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. 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). For the most up-to-date information, please refer to the interactive fault map. The epicenter was along the Calavaras Fault and 9 … Such an earthquake could unexpectedly change people’s lives and impact the Bay Area’s infrastructure and economy, but updated building codes and … #5501 Armstrong, C.F., 1979, Coyote Lake earthquake of 6 August 1979: California Geology, v. 32, no. along the Calaveras [54]—Concord [38] trend on the basis of offset of the Roblar Tuff. %%EOF 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. 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. 0000002930 00000 n 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. In 1979, the 5.7M Coyote Lake Earthquake ruptured to the south of the 1984 and 1911 earthquakes. %PDF-1.4 %���� So it's probably worth knowing where the major fault lines in the Bay Area are. Leyden Creek (site 54-2). 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. 0000003006 00000 n The Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. The initial earthquake, which occurred at a depth of 3.5 miles, was 3 miles away from San Jose and 8 miles from Gilroy. 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 USGS continuously monitors their activity. 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. x�b```f``����� �� Ȁ �@1�hPRPb2:�ɠ? The Calaveras fault produced the M6.2 Morgan Hill Earthquake in 1984. The white lines indicate faults recognized by the USGS. 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 Calaveras and Hayward faults are major components of the San Andreas fault system in the San Francisco Bay region. 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). startxref 0000002446 00000 n 0000001941 00000 n 32, p. 248-251. The reservoir sits atop a major branch of the San Andreas Fault system called the Calaveras Fault. These faulted deposits range in age from pre-Holocene to modern. The white lines indicate faults recognized by the USGS. The USGS said there was a low likelihood of casualties or damage. San Diego. Page (1982 #5521) estimated that cumulative late Cenozoic dextral offset is about 20±4 km. The Calaveras fault, part of the San Andreas fault system, is one of the most seismically active faults in central California. 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 Digging a paleoseismic trench at Tule Pond on the Hayward fault. 0000006320 00000 n 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. The surface trace is offset by several kilometers from the deep portion of the fault 3-5 km below ground (blue line). 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. 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 … 0000002412 00000 n This fault and its southern continu- ation, the Paicines fault, are part of right-slip fault zones that branch northeastward from the … There are 2 detailed studies for the Northern Calaveras section. Sarna-Wojcicki (1992 #5265) reported about 13±7 km of cumulative dextral offset in the past 6 m.y. USGS A magnitude 3.7 earthquake was followed by a 3.6 within one minute near Morgan Hill, Calif. on … 68 14 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. Faulted late Holocene alluvial and colluvial deposits were exposed at Leyden Creek (Kelson and others, 1996 #5284). Below is a list of creepmeters, from North to South, located on the San Andreas, … 54a Last Review Date: 1999-03-04 trailer Here the estimated deep slip rates drop from 15 to 6 mm/yr on the Calaveras fault… Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismic creep. This section is 43 km of a total fault length of 156 km. <]>> As of January 12, 2017, the USGS maintains a limited number of metadata fields that characterize the Quaternary faults and folds of the United States. Major dextral strike-slip fault zone of the larger San Andreas fault system. 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. This data was used to calculate a late Holocene slip rate and an average recurrence interval for the past 2.5 k.y. Alternatively, the slip may continue northward along reverse and dextral-reverse faults in the East Bay Hills (Page, 1982 #5521). 0000002685 00000 n A study by Kelson and others (1996 #5284). The Calaveras Fault splays away from the San Andreas Fault about 10 miles south of Hollister near the town of Paicines, California. In the past 200 years, the southern half of the central section of the Calaveras fault has been the most active part of the fault, according to the USGS. Within a minute, it was followed by a magnitude 3.6 quake along the Calaveras Fault in Santa Clara County. Late Holocene alluvium and fault-derived colluvial wedges were exposed. The aftershock had a depth of 3.2 miles. 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 Calaveras Fault is part of the greater San Andreas Fault System in the San Francisco Bay region. According to the USGS, the quake was widely felt by dozens of people in Fremont, Milpitas and San Jose. According to the USGS, there are seven "significant" faults in the Bay Area: the San Andreas Fault… 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. The fault cuts through the towns of Walnut Creek, San Ramon, Dublin, Pleasanton, Sunol, and Hollister. 0000000016 00000 n Source: GNU records (USGS DDS-6; Menlo GNULEX). 0 The fault extends northward through the Diablo Range for about 90 miles to the vicinity of Danville. The surface trace is offset by … (for section) versus N31°W (for whole fault). Calaveras fault zone, Northern Calaveras section (Class A) No. xref 0000000576 00000 n The Bay Area fault system and the spot (red star) where the Hayward Fault branches off from the Calaveras Fault. 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 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 San Ramon segment (Figure 1) is the dominant … The surface trace is offset by several … The white lines indicate faults recognized by the USGS. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismic creep. U.S. Geological Survey (USGS) studies show that similar Hayward Fault quakes have repeatedly jolted the region in the past and that the fault may be ready to produce another magnitude 6.8 to 7.0 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. H��W�r�H��+jND�0�e�$��-�#��s��P"�$,`�d������3^�Z�r�̗Y/��Df7,�W���Ul"��.�؄��O�iT�Y}[�f���5�. 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. 0000008989 00000 n 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. 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 U.S. Tsunami Warning System said there was no tsunami threat. !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 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. 0000001226 00000 n 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). 125–850 yr (average recurrence for past 5 k.y.). 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