Observing how seismic waves travel along a complex fault zone can reveal how fault segments might be connected at depth. USGS issued a forecast for the continuing afterslip for some homes that was included in the report for FEMA. This event was of great interest to seismologists, especially at the Berkeley Seismolgical Laboratory. At 6.0 on the moment magnitude scale and with a maximum Mercalli intensity of VIII ( Severe ), the event was the largest in the San Francisco … The California Integrated Seismic Network detected the South Napa earthquake immediately, and the first ShakeMap, issued four minutes after the earthquake, depicted the violent shaking in the immediate area. The change occurred within 1 hour after earthquake, but the discharge amount returned to normal within a few days. Rivers and streams in the area were flowing at record lows at the time of the quake because of the continuing drought, so when water began to flow again in some previously dry surrounding creeks and streams in the aftermath of the South Napa Earthquake, it prompted many nearby residents to scratch their heads. ), -written by Lisa Wald, U.S. Geological Survey. The highest intensities were MMI VII-VIII in the city of Napa and extending a littler farther north. The three largest were a M3.9 on August 26, a M3.2 a week after the mainshock on August 31, and then a M4.1 10 months later on May 22, 2015. After the 2014 South Napa Earthquake, approximately half the households in the city of Napa and in western Vallejo that reported an injury stated that the injury occurred dur-ing cleanup activities. Damage to structures decreased with distance from the rupture. Overview. Mapped faults and seismicity (magnitude 3+, 1947-2007) prior to the August 24, 2014 South Napa earthquake. Within days of reaching their peak, the water flows in surrounding creeks returned to pre-earthquake levels. Following the South Napa Earthquake on August 24, 2014, the Earthquake Engineering Research Institute (EERI) convened a small team of researchers to develop an approach for studying the resilience of businesses impacted by major earthquakes. Initially, the fault afterslip was rapid and extended into at least the southern part of the Browns Valley neighborhood in the city of Napa. M 6.0 - South Napa After the earthquake, one or more types of traumatic exposure were reported among 27% and 4% of Napa and western Vallejo households, respectively; This earthquake was unusual for its size, because it had a relatively long surface rupture of 12.5 km (8 mi) with a significant amount of surface slip (up to 46 cm; or 18 in). The shaking was lighter in Sonoma, Glen Ellen, and St Helena, where there was little damage. A smaller magnitude 5.0 earthquake on the same fault had damaged the city of Napa in 2000. (Public domain.). Seismicity in the Napa area 1973-2015, all magnitudes. Aftershocks during the first week after the mainshock. There was no evidence for the shaking being strongly amplified in any particular pockets of the downtown area. (Public domain.). Previous smaller earthquakes in the area also triggered relatively few aftershocks for their size, suggesting that this area doesn’t produce many aftershocks. Once fully implemented in the western U.S., the advance warnings of a few seconds up to a minute or more provided by the ShakeAlert system can be enough to slow public transit systems, open fire-house doors, and allow people to “Drop, Cover and Hold On.” Although there were no trains running at 3:20 a.m. when the earthquake happened, the Bay Area Rapid Transit (BART) system’s automated train-stopping system did successfully activate when the warning was received. Twitter. 2014 South Napa Earthquake Retrospective. (Public domain. Afterslip is a slow movement on the fault, and it is yet unclear whether it is associated with, or independent of, the aftershocks. It was the largest earthquake to hit the Bay Area since the 1989 World Series quake. An earthquake measuring an estimated 6.0 struck southern Napa County at 3:20 a.m. on Aug. 24, 2014 with widespread reports of damage throughout … “Did You Feel It?” community intensity map indicating the severity of shaking felt by people in central California during the South Napa Earthquake in 2014. Afterslip rates decreased dramatically in the months following the earthquake and is still being monitored by the USGS. maps compiled from these personal accounts, reflected peak shaking intensities up to a “severe” level, just a little bit less than the “violent” shaking calculated in the instrument-generated ShakeMaps. This is not an unusual phenomenon in areas with natural springs and geothermal features. (see directivity). The timing of the earthquake was not only near the end of California’s normally dry season, but also during a multi-year-long severe drought. These recordings are being used, in part, to better understand the performance of residences and older masonry buildings that have been retrofitted. These maps are used by federal, state, and local organizations, both public and private, for post-earthquake response and recovery, public and scientific information, as well as for preparedness exercises and disaster planning. the sedimentary basin - soft sediments amplify the shaking. Nicholas George looks under a buckled highway just outside Napa. It also had a large amount of afterslip, and fewer aftershocks than average for an earthquake of its size. Or, try our Real-time Notifications, Feeds, and Web Services . The South Napa Earthquake caused extensive damage through both ground shaking and surface cracking (rupture). First, to put the South Napa earthquake in context, the West Napa fault, which was the causative fault, is part of the large San Andreas Fault Zone (SAFZ) system. Almost three years have passed since the 2014 magnitude-6.0 South Napa earthquake. Frequently Asked Questions (FAQs) for Tenants After the 2014 South Napa Earthquake To aid tenants who have been affected by the 2014 South Napa Earthquake. (Josh Edelson/AFP/Getty Images) No other surface features were found, such as evidence of liquefaction or landslides. One year ago, the largest earthquake in over 25 years hit the San Francisco Bay Area, causing significant damage in California’s famous Napa Valley. Yountville, Vallejo, and American Canyon were also damaged. Warmer colors represent stronger shaking. Olivia Allen-Price. It may extend further north or south and may connect with other fault zones. Geologic Hazards Science Center, Golden, Colorado. Sometimes a single fault segment will slip and cause an earthquake, and other times many fault segments slip in unison, causing a larger earthquake. USGS PAGER Assessment for the 2014 South Napa Earthquake with initial estimates of fatalities and economic loss. Geographic Names Information System (GNIS), Mapping, Remote Sensing, and Geospatial Data. The South Napa earthquake included a few small segments that ruptured together to produce the M6 earthquake.. The sharp rise starting on August 24 reflects an increased streamflow due to the South Napa Earthquake. (Public domain.). The 6.0-magnitude quake struck at 3:20 … (Josh Edelson/AFP/Getty Images) Kids skateboard over buckled roads in a residential neighborhood of Napa. In response to the earthquake, California Earthquake Clearinghouse established a physical clearinghouse location in Napa, CA from August, 24 to August 26, 2014. Numerous vehicles were trapped by fallen carports at the Charter Oaks apartments on Browns Valley Road in Napa, Calif., following the South Napa earthquake Sunday morning, Aug. 24, 2014. Facebook. The computed instrumental intensities agreed well with those reported by residents. After the earthquake, PEER summarized various preliminary observations, in which the following ground motion The discharge of springs and groundwater to these streams began within an hour after the earthquake, increasing intermittently from 0.1 to nearly 3 cubic feet per second within a couple of weeks. The drought-induced low water table and dry ground inhibited landslides and liquefaction that can occur during earthquakes of this size, sparing the area greater damage than could have been. USGS Geologists inspecting fault trace in a trench dug across one of the ruptures from the 2014 South Napa earthquake. (Public domain. Copy Link. The earthquake was unusual for the length of surface rupture (8 miles), the amount of surface slip (up to 18 inches), and the large afterslip that followed the earthquake (up to 14 inches). And I am listening to KTVU TV News right now, … USGS Home Contact USGS Search USGS. In addition, a M3.0 earthquake occurred on August 5, 2014, 19 days before the M6.0, which, in retrospect, some scientists/seismologists might consider a foreshock. Scientists found that some of the fault segments that ruptured on the morning of August 24 had been previously mapped as part of the West Napa fault system, but the rupture also extended northward where no faults had been mapped before. For example, the surprising amount of afterslip observed gave scientists a new way to look at and forecast continuing hazards in the weeks to months, after the earthquake occurred. August 28, 2014 Sunday morning, the San Francisco Bay area awoke to shaking; a 6.0 magnitude earthquake, California's strongest since the 1989 Loma Prieta earthquake… Key Recovery Factors for the August 24, 2014, South Napa Earthquake. Damage to wood-frame houses was mostly broken or cracked chimneys and failure of cripple walls (see Additional Resources below), short walls in the crawl space between the foundation and the floor. The earthquake fault rupture extended northward from the epicenter, directing much of the seismic energy toward the city of Napa. 1: What does it mean if my apartment building was red, yellow, or green tagged*? In addition, a M3.0 earthquake occurred on August 5, 2014, 19 days before the M6.0, which, in retrospect, some scientists/seismologists might consider a foreshock. This anniversary of the event is a time to look back at what the U.S. Geological Survey and its scientific partners have learned from the South Napa Earthquake. Within 1 hour after the earthquake, over 25,000 citizen scientists entered their data on the website, creating a map of the distribution of shaking that they felt. _ having even a few seconds of warning before an earthquake In addition, airborne and ground-based LIDAR data were collected in areas known to have surface cracks to measure and describe what happened. Office of Communications and Publishing12201 Sunrise Valley DriveReston, VA 20192United StatesPhone: 703-648-4460. There is no denying that. The magnitude 6.0 earthquake occurred early in the morning on August 24, 2014, on the West Napa Fault. The M6.0 South Napa earthquake occurred on August 24, 2014. But this was no small earthquake, and as the small representative sample of Jawbone© data shows, many residents had trouble going back to sleep after this one. Hurricane Marie peaked on 8/24 at 21 UTC - about 2 hours from the Peru earthquake. The 24 August 2014 Mw 6.0 South Napa earthquake occurred on … One year ago, the largest earthquake in over 25 years hit the San Francisco Bay Area, causing significant damage in California’s famous Napa Valley. The SAFZ is not a simple, single fault, but rather a complex collection of smaller fault segments that collectively accommodate the horizontal movement between the North American Plate and the Pacific Plate. Data collected from airborne LIDAR were used to look for effects on the ground surface. LOS ANGELES _ In a land where the mildest rumble elicits an anxious question _ "Did you feel that?" Geographic Names Information System (GNIS), Mapping, Remote Sensing, and Geospatial Data, map of the distribution of shaking that they felt, Earthquake Strengthening of Cripple Walls in Wood-Frame Dwellings, the rupture direction along the fault - to the north and updip towards Napa. After the 2014 South Napa Earthquake, approximately half the households in the city of Napa and in western Vallejo that reported an injury stated that the injury occurred during cleanup activities. This lack of ground failure was attributed to the lack of rainfall in the area; a shallower water table would have made the surface material less stable and more prone to ground failure. (Public domain.). Immediate Impact The city of Napa was very strongly shaken: many historical masonry buildings and older residences were damaged. The following day (almost 24 hrs later), the same feature had 11 cm (4 in) of offset. Earthquake Science Center, Menlo Park, California. Afterslip causes additional damage to manmade structures, such as roads, but does not release seismic waves and cause shaking. Hydrograph showing stream flow in cubic feet per second on USGS streamgage on Sonoma Creek near Agua Caliente, from about August 23 – September 13, 2014. For further details, see Groundwater Effects from Earthquakes. The South Napa earthquake was very well recorded and produced a number of strong ground motion recordings that are of considerable interest to the engineering community. In the case of re trospective full-waveform inversions, a network with station spacing of 10km within the epicentral distanc e of 30km is able to provide adequate stable key source parameters if the preestimated hypocenter and fault ori entation are accurate of ±5km and ±15°, respectively. (Credit: Tim Dawson, California Geological Survey. On August 24, 2014, a magnitude-6.0 earthquake occurred in Napa, California. This detailed assessment of the South Napa earthquake and the West Napa Fault system helps scientists assess future earthquake hazards in the area so communities can better prepare for them. The WNFZ was mapped as a 46-kilometer long segment of subparallel fault traces from Vallejo to Saint Helena, California. Skip Links. The earthquake woke people throughout northern California, in cities as far away as Sacramento and Santa Cruz. The August 24, 2014, South Napa earthquake (M6.0) produced significant damage resulting from shaking, fault rupture, fault afterslip, and ground deformation. The event was the largest in the San Francisco Bay Area since the 1989 Loma Prieta earthquake. ), These two photos showing evidence of afterslip were taken where the fault crosses Highway 12 (south side of the highway) at Cuttings Wharf Road. With one fatality, and approximately a half billion dollars of economic damage, the city of Napa is still recovering from last year’s quake. The prototype earthquake early warning “ShakeAlert” system provided about 5 seconds of warning to test users 23 miles away in Berkeley and a 9-second warning to San Francisco, 31 miles away. performance of buildings after earthquakes. All of the faults and/or imagery lineaments shown as heavy green lines on this map may be considered to have a low level of afterslip hazard. (Public domain. There was one fatality due to the earthquake, and at least $500 million in economic losses. The Did You Feel It? An additional 14+ cm (5.5+ in) of slip was measured during the first 24 hours, and up to 20 cm (8 in) after 48 hours, mainly on southern half of the main fault strand. Residential structures and wineries surrounding this area were significantly damaged. The following summary is what USGS (and USGS-funded) scientists have learned from the data one year after the earthquake. (DYFI) webpage bookmarked, so as soon as the shaking stopped, they started reporting their experience of the shaking on DYFI. Also, fault strands that had been mapped prior to this earthquake were not thought to be highly hazardous. The first PAGER Assessment (providing fatality and economic loss impact estimates) was issued 13 minutes after the earthquake, and accurately forecast a low level of human casualties, but significant economic losses in the area. ShakeCast is an application for automating ShakeMap delivery to critical users and for facilitating notification of shaking levels at user-selected facilities. ), Napa Valley area red- and yellow-tagged structures shown as red and yellow squares. An Instrumental Intensity “ShakeMap,” depicts the ground shaking produced by the 2014 South Napa earthquake. A few homes even shifted off of their foundations, which can be due to the failure of the cripple walls, which drop the floor to the foundation and sometimes allow houses to slide off the foundation. Ground shaking was significant with accompanying maximum Modified Mercalli Intensities between VIII and IX. Copy Link. Many California residents have the Did You Feel It? The relative motion on this fault is not well known but thought to be about 1 mm/yr (0.04 in/yr). These activities resulted in a comprehensive understanding of fault motion and ground response, in ways that could not have been imagined the last time (1989) there was a large quake in the San Francisco Bay Area. Cullen 328 Let's discuss it 05:47, 26 August 2014 (UTC) This article in the San Jose Mercury News, published about 80 miles away, specifically mentions that "South Napa Earthquake" is emerging as the accepted name. Some fault strands that broke in residential areas and damaged homes, had not previously been mapped. The first offset measurement was taken the day of the earthquake - about 6 cm (2 in) of right-lateral offset. Email. California Governor Jerry Brown called it the "South Napa Earthquake" in his official emergency declaration, widely reported in the press. The seismic hazard posed by the West Napa Fault System is still being evaluated. It provides an excellent example for studying crustal strain associated with the earthquake cycle of a strike-slip fault with clear societal relevance. Many others spread out across the Napa Valley and surrounding area to collect additional data such as fault rupture expressed on the ground surface, as well as shaking induced damage to buildings and infrastructure. These measurements are probably minimums for the zone since the deformation was probably distributed over an area of several meters wide. Public domain. Ultimately 41,000+ citizens shared their experiences, with the farthest felt report 300 km (186 mi) to the east in Reno, NV. The sharp rise starting on August 24 reflects an increased streamflow due to the South Napa Earthquake. The California Geological Survey (CGS) is currently remapping the West Napa Fault System in concert with fault excavation (trenching) studies carried out by the USGS and CGS to evaluate the prehistoric record of rupture on the various fault strands. 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