They came in a flurry of orange, descending on this quake-ravaged neighborhood with brooms, shovels and dozens of hands. 
 
 Then they formed a human chain in Lori Lemieux' frontyard, passing the crumbled bricks of her home's fallen chimney into a waiting truck bed. 
 
 The retired clerical supervisor watched in awe Monday morning. She and her husband had lost every wineglass in Sunday's 6.0 magnitude shaker, the largest to strike the Bay Area in a quarter-century. Furniture splintered. Worse still, mementos of their daughter, who died a decade ago when she was 17, were destroyed. 
 
 And now, strangers were helping. 
 
 "When you have something so devastating happen, to see this teamwork is just awesome," she said of the dozens of Home Depot workers from a number of Northern California communities who offered their help. "Blessings do happen." 
 
 Caption Raw: Aerial Look at Napa Quake Damage Two days after a strong and damaging earthquake hit the Napa Valley area, California's wine capital is working to recover. Two days after a strong and damaging earthquake hit the Napa Valley area, California's wine capital is working to recover. Caption Some Priceless Napa Vintages Lost In Napa Quake Some Priceless Napa Vintages Lost In Napa Quake Some Priceless Napa Vintages Lost In Napa Quake Caption As Aftershocks Continue to Hit, Cleanup Efforts Underway Following Napa 6.0 Earthquake Cleanup efforts were underway in the Bay Area on Monday, one day after a magnitude-6.0 earthquake along the West Napa Fault prompted Gov. Jerry Brown to declare a state of emergency., Cleanup efforts were underway in the Bay Area on Monday, one day after a magnitude-6.0 earthquake along the West Napa Fault prompted Gov. Jerry Brown to declare a state of emergency., Caption Brown Declares State Of Emergency Following 6.0 Magnitude Quake In Napa Valley Brown Declares State Of Emergency Following 6.0 Magnitude Quake In Napa Valley Brown Declares State Of Emergency Following 6.0 Magnitude Quake In Napa Valley Caption Surveillance Cameras Captures Earthquake Damage Surveillance Cameras Captures Earthquake Damage Surveillance Cameras Captures Earthquake Damage 
 
 The volunteers had company. A day after the temblor, inspectors had deemed 70 buildings here uninhabitable. The number of people treated for injuries had risen to 208, and schools remained closed. But residents and outsiders alike had found a common calling. 
 
 "When you meet people who are helping each other, there's no difference between religions or between colors," said Premysl Balaz, a 33-year-old engineer from the Czech Republic who was a week into a San Francisco vacation when the earthquake hit. 
 
 He drove up, found the temporary volunteer center, and was dispatched Monday to help build a database of red-tagged homes. 
 
 "Everyone is connected through the idea that they want to help," Balaz said. "I love the energy about it." 
 
 It didn't take long for the helpers to amass. 
 
 At Grace Church of Napa Valley on Sunday morning, congregants prayed and then made a list. Up top was a couple whose home sits directly on the fault. 
 
 After the earth split, Tim and Ann Whitlock's two-story house ended up six inches in front of its foundation. Big cracks zigzagged up the interior walls, and the sidewalk buckled into the shape of a tepee. 
 
 Throughout the day, fellow congregants — about 100 of them — helped pack everything into boxes and big plastic containers. 
 
 "Who says you can't move in six hours?" said Ann Whitlock. 
 
 Across town, Patricia Trimble was wading through a mess of broken pottery and glass at the Roost, her downtown vintage store, when a stranger walked in. 
 
 "He said he was drawn to me. He quoted Yeats," Trimble said of Marc Liotta, a Walnut Creek contractor with a near-addiction to reaching out to strangers. Liotta picked up the bags of debris and tossed them in the bed of his silver Toyota Tundra for a courtesy run to the dump. 
 
 "And you know what he did then?" Trimble said Monday as she listened to the melancholy sounds of Rickie Lee Jones in her quickly shaping-up boutique. "He went to my house and offered his help there." 
 
 Liotta, whose card reads "The Closet Magician," is semi-retired. In addition to building closet organizing systems, he has volunteered for Habitat for Humanity (as has Trimble) and flown to Haiti to offer his assistance after the earthquake. 
 
 "I was sort of languishing around here watching television and said, 'I'm gonna just go up there,'" said Liotta, 69, who was tipped off to Trimble's plight by the plywood on her window. 
 
 By Monday morning, more help arrived. At the volunteer center in the Grace church gym, Gregg DesElms welcomed a woman who said she'd taken the day off work. 
 
 He started to explain that he didn't have anywhere to send her or Balaz, the visiting engineer. Then DesElms' cellphone rang. 
 
 "Yes," he said. "I have two people here right now, and they're ready to go." 
 
 He hung up and turned to Balaz. 
 
 "How's your English and your typing?" he asked. 
 
 "So-so," Balaz said. 
 
 The police chief needed help entering numbers and addresses of red-tagged structures. 
 
 "Oh, I'm good with numbers," Balaz said, smiling. "I'm in, I'm in." 
 
 By afternoon, "Cartoon" Danny Roszell was offering his services to merchants. He tends to travel with a broom, though he insists he is no witch, but "a leprechaun incarnate." A window painter by trade, the Berkeley resident had come to Napa 10 days ago to help a friend with her house and look for gigs adorning glass with images of the grape harvest. 
 
 After the quake, he decided to put his broom to use. He showed up downtown in a white wool top hat adorned with a live flower bouquet. 
 
 "It's what I do," he said, of his sweeping habit. "It's a kind of meditation." 
 
 A few blocks away, Rod Wieldraayer was hauling free materials from the Napa Home Depot store to about 60 volunteers as they hopscotched through town. 
 
 Wieldraayer, the store manager, also happens to live here. The company often organizes its workers in small volunteer armies, so Monday's massive mobilization came naturally. 
 
 The bed of his truck was already loaded with a stack of plywood, crates of water and garbage bags when his cellphone rang. It was his district manager. 
 
 "Boxes? Medium boxes?" Wieldraayer said. "I'm on it." 
 
 A family with a red-tagged home needed them, so Wieldraayer returned to the store to fetch them and renew his supply of angle brackets, for residents now scrambling to secure their heavy furniture to the wall. 
 
 Meanwhile, in the Browns Valley neighborhood, where Lemieux lives, the crew was moving street to street. 
 
 Within no time, they had re-stacked a tumbled-down wood pile, hauled off debris from two other fallen chimneys, and disassembled a hulking planter once built onto Darcie Blair's front porch. 
 
 Blair, 45, a single mother with a 4-year-old daughter, lived in Northridge when the big quake struck there in 1994, but said she never felt anywhere close to the support she is getting in Napa. Within minutes of their departure, she had posted pictures of the Home Depot helpers on Facebook. 
 
 "The kindness of strangers just keeps on amazing me," she wrote. "As my daughter and I continue to clean up here in Napa, the folks from Home Depot just completely dismantled and hauled away for free a large part of our front porch. 
 
 "Thank you, good neighbors. You rock." 
 
 lee.romney@latimes.com 
 
 Twitter: @leeromney 
 
 marisa.gerber@latimes.com 
 
 Twitter: @marisagerber ||||| A strong, 6.0-magnitude earthquake jolted Northern California yesterday (Aug. 24) at 3:20 a.m. local time. The earthquake's epicenter was a few miles south of Napa Valley's renowned wineries, and the quake busted barrels and bottles of precious vintages. More than 170 people were injured, and 100 homes are now uninhabitable, the state Office of Emergency Services said Sunday. 
 
 In the first uncertain minutes, a seismologist at the U.S Geological Survey's Bay Area headquarters pinned the blame on the Franklin Fault, which has been inactive for thousands of years. 
 
 By morning, the sun lay bare what darkness hid: Buckled pavement and cracked curbs lined up along the West Napa Fault for up to 10 miles (16 kilometers). After inspecting the damage, California state geologist John Parrish declared that Sunday's earthquake occurred on the West Napa Fault, not the Franklin Fault. The USGS concurred, tweeting Sunday that the Browns Valley section of the West Napa Fault was the likely culprit. [See photos of damage from the Napa earthquake] 
 
 The results are still preliminary, and geologists will make a definitive call in the next few days. However, the early false start highlights how both high-tech instruments and old-fashioned groundwork remain important in the aftermath of an earthquake. 
 
 Which fault? 
 
 Yesterday's earthquake struck near the Napa Airport, in the San Pablo Bay marshes. The USGS precisely located the epicenter in just a few minutes, thanks to the region's dense seismic monitoring network, said Tom Brocher, director of the USGS Earthquake Science Center in Menlo Park, California. But which fault was at fault? 
 
 Many suspects appear on state earthquake maps. One is the West Napa Fault, which stretches 35 miles (57 km) from the city of St. Helena south to San Pablo Bay, according to a USGS report published in 2008. Among a handful of other possibilities, the Franklin Fault also stands out. This fault begins near the epicenter of the recent quake, and then cuts south across San Pablo Bay. 
 
 West Napa or Franklin? That 4 a.m. guess blaming the Franklin Fault soon seemed wrong. As damage reports poured in, scientists zeroed in on the West Napa Fault's Browns Valley branch. 
 
 This fault traces the western margin of the Napa Valley and cuts through the Browns Valley neighborhood of Napa. Along with the damaged streets, many of the city's water main breaks were in the Browns Valley area, according to Napa Valley officials. The Browns Valley branch pierces the Napa River at Cuttings Wharf. Another strand of the West Napa Fault lies east of the river and runs through the Napa Airport. 
 
 Map of Napa Valley region faults. Credit: USGS 
 
 Why it happened 
 
 The West Napa Fault is part of the huge fault zone extending outward from the San Andreas Fault, which lies about 31 miles (50 km) west of Napa Valley. The San Andreas marks the boundary where the Pacific and North American tectonic plates grind past one another. The West Napa Fault is sandwiched between two larger faults: the Hayward-Rodgers Creek Fault and the Concord-Green Valley Fault. [Photo Journal: The Gorgeous San Andreas Fault] 
 
 "The plate boundary is really quite wide and quite complicated, and the plate motion is accommodated by a wide network of faults," Brocher told Live Science. 
 
 The tectonic tension between the plates trickles inland to the West Napa Fault. An earthquake occurs when this built-up strain is unleashed. The fault parallels the San Andreas, and like the San Andreas, it is a series of slashes in the earth, not a single crack. (Each fault has more than one segment running in parallel.) Each fault is also of a type called right-lateral strike-slip, which means one side of the fault leaps horizontally to the right during an earthquake. 
 
 Within the last 11,000 years, the West Napa Fault has created cliffs and ridges called scarps, a sign of past seismic activity. But this fault has never jolted valley residents in historic times. 
 
 The last earthquake to rattle the Napa Valley struck on Sept. 3, 2000. This magnitude-5.1 earthquake occurred 10 miles (16 km) northwest of Napa, near Yountville, on a previously unknown fault. 
 
 No one knows how often earthquakes rumble through Napa Valley. The West Napa Fault and others nearby have never received the detailed detective work that geologists lavish on faults in the densely settled Bay Area. A 2008 estimate of Bay Area earthquake probabilities conducted by scientists and engineers for the state of California did not include the West Napa Fault. 
 
 "It is known to be an active fault, but it certainly has not been viewed as one of the major players in the Bay Area," Brocher said. 
 
 Napa's 6.0-magnitude earthquake is the biggest quake in California since the magnitude-6.7 Northridge earthquake in 1994, and the biggest in Northern California since the 1989 Loma Prieta earthquake, a magnitude 6.9. 
 
 Collecting clues 
 
 But the South Napa earthquake could have been worse. Only part of the West Napa Fault broke open. If the entire fault had ripped, the earthquake would have been more powerful. 
 
 "I have to say, as much as the earthquake was large and had a widespread impact, it's not as bad as it could have been," Mark Ghilarducci, director of California's Office of Emergency Services, said during a press conference Sunday. 
 
 Though the actual earthquake rupture only lasted four seconds, there was strong shaking in Napa because the valley floor is lined with soft river soils that amplify earthquake waves. Also, the fault zipped open from south to north, directing the earthquake energy toward the city. "It looks like it went northwest and up from the dot on the map that shows where the earthquake nucleated," Brocher said. [13 Crazy Earthquake Facts] 
 
 Early Sunday morning, geologists from the USGS, the California Geological Survey and local universities were recording the surface damage before road crews started their repairs. This information will help researchers understand the earthquake's progress during the brief seconds the fault opened and closed. 
 
 On the high-tech side, it will take a few more days to measure how much the valley moved during and after the earthquake, using GPS and satellite measurements. An initial GPS report indicated 4 inches (10 centimeters) of shift near the earthquake's epicenter, Brocher said. 
 
 Small earthquakes called aftershocks continue to strike along the West Napa Fault. These small quakes cluster along the fault zone and illuminate the hidden underground parts of the fault, and will help scientists nail down which fault caused the quake. 
 
 "The locations of the aftershocks indicate that it ruptured the West Napa Fault, but it is not clear yet which strand of that fault broke," said Felix Waldhauser, a seismologist at the Lamont-Doherty Earth Observatory in Palisades, New York. "Over the next couple of days we should have a better picture." 
 
 The earthquake is likely to bring new focus to Napa Valley's earthquake hazard. The California Geological Survey had already begun new studies on the Browns Valley branch earlier this year, and more researchers will likely begin studies analyzing the earthquake and its causes. 
 
 The quake also highlighted the most forward-reaching technology in California's quake arsenal. 
 
 The first jolt triggered the prototype earthquake early warning system at the University of California, Berkeley's Seismological Laboratory. The lab received a 10-second warning before the shaking started, said Lab Director Richard Allen. The warning could have been improved with an upgrade to the ShakeAlert system, which would have boosted the response time of the slowest seismometer by 2.5 seconds, Allen said. The state legislature approved a bill to expand the system statewide in 2013, but the Office of Emergency Services must find $80 million to pay for it. 
 
 "While the system clearly worked, the warning could have been twice as fast," Allen said. 
 
 Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on Live Science. ||||| NAPA, Calif. (AP) — The San Francisco Bay Area's strongest earthquake in 25 years struck the heart of California's wine country early Sunday, igniting gas-fed fires, damaging some of the region's famed wineries and historic buildings, and sending dozens of people to hospitals. 
 
 A Napa firefighter inspects mobile homes that were destroyed Sunday, Aug. 24, 2014, at the Napa Valley Mobile Home Park, in Napa, Calif. A gas fire destroyed four homes at the park after an earthquake... (Associated Press) 
 
 A mailbox is all that remains of one of four mobile homes which were destroyed in a gas fire Sunday, Aug. 24, 2014, at the Napa Valley Mobile Home Park, in Napa, Calif. A large earthquake caused significant... (Associated Press) 
 
 Steve Brody inspects damage to the interior of his mobile home after an earthquake Sunday, Aug. 24, 2014, at the Napa Valley Mobile Home Park, in Napa, Calif. A large earthquake caused significant damage... (Associated Press) 
 
 Nola Rawlins drinks coffee in the office of the at the Napa Valley Mobile Home Park Sunday, Aug. 24, 2014, in Napa, Calif. Rawlins home was one of 4 destroyed by a gas fire at the mobile home park, the... (Associated Press) 
 
 Police cars block the street outside a heavily damaged building following an earthquake Sunday, Aug. 24, 2014, in Napa, Calif. A large earthquake caused significant damage in California's northern Bay... (Associated Press) 
 
 Jorge Sanchez looks over damage to the main post office following an earthquake Sunday, Aug. 24, 2014, in Napa, Calif. A large earthquake caused significant damage in California's northern Bay Area early... (Associated Press) 
 
 Jean Meehan looks over the damage to her JHM Stamp and Collectibles store following an earthquake Sunday, Aug. 24, 2014, in Napa, Calif. A large earthquake caused significant damage in California's northern... (Associated Press) 
 
 Nina Quidit cleans up the Dollar Plus and Party Supplies Store in American Canyon Calif. after an earthquake on Sunday Aug. 24, 2014. Quidit and her husband were woken up in the early morning hours by... (Associated Press) 
 
 Nina Quidit cleans up the Dollar Plus and Party Supplies Store in American Canyon Calif., after an earthquake on Sunday, Aug. 24, 2014. Quidit and her husband were woken up in the early morning hours... (Associated Press) 
 
 Steve Brody inspects damage to the interior of his mobile home after an earthquake Sunday, Aug. 24, 2014, at the Napa Valley Mobile Home Park, in Napa, Calif. A large earthquake caused significant damage... (Associated Press) 
 
 Janelle Dahl and her son Austin clean up broken bottles of wine in a tasting room after an earthquake at Dahl Vineyards Sunday, Aug. 24, 2014, in Yountville, Calif. A large earthquake rolled through California's... (Associated Press) 
 
 A youngster rides his scooter over a sidewalk buckled by an earthquake Sunday, Aug. 24, 2014, in Napa, Calif. A large earthquake caused significant damage and left at least three critically injured in... (Associated Press) 
 
 Winemaker Tom Montgomery stands in wine and reacts to seeing damage following an earthquake at the B.R. Cohn Winery barrel storage facility Sunday, Aug. 24, 2014, in Napa, Calif. Winemakers in California’s... (Associated Press) 
 
 Part of a brick wall is missing from a building after an earthquake Sunday, Aug. 24, 2014, in Napa, Calif. Officials say an earthquake with a preliminary magnitude of 6.0 has been reported in California's... (Associated Press) 
 
 Grace Hardy cleans up wine bottles at nakedwines.com in Napa, Calif., following an earthquake Sunday, Aug. 24, 2014. Winemakers in California’s storied Napa Valley woke up to thousands of broken bottles,... (Associated Press) 
 
 An awning for Carpe Diem wine bar sits among rubble in Napa, Calif., following an earthquake Sunday, Aug. 24, 2014. A large earthquake caused significant damage and left at least three critically injured... (Associated Press) 
 
 The magnitude-6.0 quake, centered near the city of Napa, an oasis of Victorian-era buildings nestled in the vineyard-studded hills of northern California, ruptured water mains and gas lines, hampering firefighters' efforts to extinguish the blazes that broke out after the temblor struck at 3:20 a.m. 
 
 Dazed residents who had run out of their homes in the dark and were too fearful of aftershocks to go back to bed wandered through Napa's historic downtown, where boulder-sized chunks of rubble and broken glass littered the streets. Dozens of homes and buildings across the Napa Valley were left unsafe to occupy, including an old county courthouse, where a 10-foot wide hole opened a view of the offices inside. 
 
 College student Eduardo Rivera said the home he shares with six relatives shook so violently that he kept getting knocked back into his bed as he tried to flee. 
 
 "When I woke up, my mom was screaming, and the sound from the earthquake was greater than my mom's screams," the 20-year-old Rivera said. 
 
 Gov. Jerry Brown declared a state of emergency for southern Napa County, directing state agencies to respond with equipment and personnel. President Barack Obama was briefed on the earthquake, the White House said, and federal officials were in touch with state and local emergency responders. 
 
 The temblor struck about six miles south of Napa and lasted 10 to 20 seconds, according to the United States Geological Survey. It was the largest to shake the San Francisco Bay Area since the magnitude-6.9 Loma Prieta quake struck in 1989, collapsing part of the Bay Bridge roadway and killing more than 60 people, most when an Oakland freeway collapsed. 
 
 Queen of the Valley Medical Center in Napa, where an outdoor triage tent was set up to handle the influx, reported treating 172 people in the emergency room, although hospital officials could not say how many of them were there for bruises and cuts suffered in the quake and how many for more routine injuries and illnesses. 
 
 Twelve people were admitted for broken bones, heart attacks and other problems directly related to the earthquake, including an adult who remained in critical condition on Sunday night and a 13-year-old boy. 
 
 The teen was hit by flying debris from a collapsed fireplace and had to be airlifted to the children's hospital at the University of California Davis hospital for a neurological evaluation. He condition was listed as serious, hospital spokeswoman Phyllis Brown said. 
 
 Napa Fire Department Operations Chief John Callanan said the city had exhausted its own resources trying to extinguish at least six fires after 60 water mains ruptured, as well as transporting injured residents, searching homes and collapsed carports for anyone trapped and responding to 100 reports of leaking gas. 
 
 Two of the fires happened at mobile home parks, including the one where four homes were destroyed and two others damaged, Callanan said. A ruptured water main there delayed efforts to fight the blaze until pumper trucks could be brought in, he said. 
 
 Nola Rawlins, 83, was one of the Napa Valley Mobile Home Park residents left homeless by the fire. No one was injured in the blaze, but Rawlins said she lost all her jewelry, papers and other belongings. 
 
 "There were some explosions, and it was burning. Everybody was out in the street," she said. "I couldn't get back in the house because they told everybody to go down to the clubhouse, so I didn't get anything out of the house." 
 
 U.S. Rep. Mike Thompson, who represents Napa, said federal and state officials had conducted an aerial survey of the area, but they wouldn't have a cost estimate for the damage until they can get on the ground and into buildings. He said that while Napa suffered the worst of it, there also was significant damage about 17 miles south on Mare Island in Vallejo, a former naval shipyard where a museum and historic homes were declared uninhabitable. 
 
 "It's bad any way you calculate it. But it could have been a heck of a lot worse," Thompson said. 
 
 While inspecting the shattered glass at her husband's storefront office in downtown Napa, Chris Malloy described calling for her two children in the dark as the quake rumbled under the family's home, tossing heavy pieces of furniture for several feet. 
 
 "It was shaking, and I was crawling on my hands and knees in the dark, looking for them," the 45-year-old woman said, wearing flip flops on feet left bloodied from crawling through broken glass. 
 
 Sunday's quake was felt widely throughout the region, with people reporting its effects more than 200 miles south of Napa and as far east as the Nevada border. Amtrak suspended service through the Bay area so tracks could be inspected. 
 
 Vintner Richard Ward of Saintsbury Winery south of Napa watched Sunday afternoon as workers righted toppled barrels and rescued a 500-pound grape de-stemmer that the quake had thrown to the ground. 
 
 "That's what happens when you're a mile from the epicenter," said Ward, who lost 300 to 400 bottles in the winery's basement. 
 
 The grape harvest was supposed to start overnight Monday, but it would now be pushed off a few days, he said. Had the harvest started a day earlier, the quake would have caught the workers among the heavy barrels when it struck, Ward said. 
 
 Mark Ghilarducci, director of the California Governor's Office of Emergency Services, told an afternoon news conference some 90 to 100 homes and buildings were deemed not habitable. 
 
 A Red Cross evacuation center was set up at a church, and crews were assessing damage to homes, bridges and roadways. The Napa Unified School District said classes were canceled for students Monday and that students would not be allowed to return to schools until they were checked. 
 
 "There's collapses, fires," said Napa Fire Capt. Doug Bridewell, standing in front of large pieces of masonry that broke loose from an early 20th-century office building where a fire had just been extinguished. "That's the worst shaking I've ever been in." 
 
 Bridewell said he had to climb over fallen furniture in his own home to check on his family before reporting to duty. 
 
 Pacific Gas and Electric spokesman J.D. Guidi said some 30,000 customers lost power after the quake hit, but that number was down to around 7,300 later in the day, most of them in Napa. He said crews were working to make repairs, but it was unclear when electricity would be restored. 
 
 The depth of the earthquake was just under seven miles, and it was followed by numerous small aftershocks, the USGS said. 
 
 On Sunday night in Southern California, a small, magnitude-3.3 earthquake hit off the region's coast. 
 
 The U.S. Geological Survey says the temblor struck at 7:50 p.m. and was centered about 5 miles southwest of San Pedro and 6 miles southeast of Rancho Palos Verdes. There were no initial reports of damages, police said. 
 
 ___ 
 
 Associated Press writers Juliet Williams in Napa, Tom Verdin in Sacramento, Sudhin Thanawala in San Francisco and Courtney Bonnell in Phoenix contributed to this report.
– People in Napa Valley, Calif., are picking up the pieces after Sunday's 6.0 earthquake wrecked scores of homes and businesses, and they're getting plenty of help from outside. Volunteers have flocked from across Northern California to assist in any way they can, reports the Los Angeles Times. The helpers include scores of Home Depot workers and an engineer from the Czech Republic who was on vacation in San Francisco when the quake struck and drove out to offer his services. "When you meet people who are helping each other, there's no difference between religions or between colors," he says. More: The damage is estimated at up to $1 billion, but wineries say they will pull through and they hope tourists won't stay away, the New York Times reports. "In the end, people who are growing grapes are farmers," says an official of an organization that represents 500 local vintners. "This is a particularly strong expression of Mother Nature, but they deal with Mother Nature every day, and they are very resilient." Dozens of homes have been declared uninhabitable and more than 250 people are recovering from injuries, but there have been no fatalities from the area's worst earthquake since 1989, the San Francisco Chronicle reports. The two most seriously injured victims, one of them a 13-year-old boy hurt by a falling chimney, are both expected to survive. Seismologists are still working to determine the exact cause of the quake, LiveScience reports. It was initially believed to be connected to the Franklin Fault—which has been dormant for thousands of years—but researchers now believe it was the West Napa Fault, part of a wide network of faults around the San Andreas Fault, which lies 31 miles away.