Latest news with #GreatSanFranciscoEarthquake
Yahoo
23-06-2025
- Science
- Yahoo
The San Andreas Fault: Facts about the crack in California's crust that could unleash the 'Big One'
When you buy through links on our articles, Future and its syndication partners may earn a commission. Quick facts about the San Andreas Fault How long is the San Andreas Fault? About 746 miles (1,200 kilometers) What was the biggest earthquake on the San Andreas Fault? The Great San Francisco Earthquake of 1906, which had a magnitude of around 7.9 When was the San Andreas Fault discovered? 1895 The San Andreas Fault is California's longest and most famous fault. At this fracture zone, two plates of Earth's crust move past each other. It stretches from the Salton Sea in Southern California to off the coast of Mendocino in Northern California. On the inland side of the fault, the North American Plate moves southeast. Toward the coast, the Pacific Plate creeps northwest. The San Andreas is capable of creating big, destructive earthquakes. Earthquakes are measured in magnitude on a scale that starts at zero. In this scale, each whole number represents an earthquake 10 times as large as the one before it. Most earthquakes under magnitude 2.5 aren't felt, while 2.5- to 5.4- magnitude quakes usually cause some shaking but not much damage. Quakes of 5.5 magnitude and higher cause damage to buildings, and earthquakes over 7.0 are considered major. In 1906, the northern section of the fault shook San Francisco and the Bay Area with a 7.9 magnitude quake, which caused a devastating fire in the city and killed more than 3,000 people, according to the U.S. Geological Survey. In 1857, the southern section of the fault shook and created a quake thought to be just as large. Only two people died, because California had a tiny population at the time. Geologists warn that the San Andreas will give off a large earthquake again — the only question is when. Over the past 3 million years, the San Andreas Fault has moved an average of 2 inches (56 mm) per year. If that rate continues, Los Angeles and San Francisco will be next-door neighbors in 15 million years! The 1857 Fort Tejon quake on the southern San Andreas Fault lasted between one and three minutes. During the 1906 Great San Francisco earthquake, 296 miles (477 km) of the fault moved. The San Andreas Fault was discovered just 11 years before the 1906 earthquake by geologist Andrew Lawson, who worked at the University of California, Berkeley. The San Andreas Fault is a "right-lateral strike-slip fault." That's a complicated way to say that if you stood on the North American Plate side of the fault facing the Pacific Ocean, the Pacific Plate side of the fault would be moving slowly to the right. At the San Andreas, the two plates are like blocks that are moving past each other and sometimes getting stuck along the way. When they get unstuck — quickly! — the result is a sudden earthquake. The fault is split into three segments. The southern segment starts northeast of San Diego at Bombay Beach, California, and continues north to Parkfield, California, near the middle of the state. A quake on this segment would threaten the highly populated city of Los Angeles. The middle section of the San Andreas is known as the "creeping section." It stretches between the California cities of Parkfield and Hollister in central California. Here, the fault "creeps," or moves slowly without causing shaking. There haven't been any large quakes on this section within recorded history, but scientists think there may have been earthquakes there at some point in the past 3 million years. Finally, the northern section of the San Andreas spans from Hollister to a special spot called the "triple junction" off the coast of Mendocino. The triple junction is where the North American tectonic plate, Pacific plate, and undersea Gorda plate meet. At this junction, the way the plates move past each other on the San Andreas Fault transforms into a different kind of geology known as a subduction zone. In the subduction zone, the Pacific Plate slides under the North American Plate instead of alongside it. The San Andreas Fault is about 746 miles (1,200 km) long and about 10 miles (16 km) deep. While the San Andreas is a giant fault that is even visible from space, if you zoom in, you'll see a network of many faults coming off the San Andreas. So the whole region is known more generally as the San Andreas Fault zone. This area includes faults like the Hayward Fault, which runs through the East Bay area. These side faults can produce their own serious earthquakes. For example, in 1868, the Hayward Fault rumbled to life with a magnitude 6.8 quake that killed 30 people. A similar quake today would affect the Bay Area, where millions of people live. A long time ago, the tectonic plate under the Pacific Ocean crashed directly into the tectonic plate carrying the continent of North America. The ocean plate dove under the continental plate, a pattern called subduction. Meanwhile, in the middle of the ocean there was a spot where molten lava, or magma, rose from inside Earth and formed brand-new crust. The place where the new crust formed wasn't very far from the subduction zone where crust got pushed back into the Earth. So about 30 million years ago, those two spots came together. The place where the new crust formed got pushed right under North America! This was a big change in how the geology worked in all of western North America. A new ocean plate was now touching North America. It was moving in a slightly different direction, so it didn't dive right under the continent. Subduction ended, and a new strike-slip fault (the San Andreas) was formed. The San Andreas Fault runs through and near many populated areas, including Los Angeles and the San Francisco Bay Area. It can produce damaging earthquakes, so scientists consider it a very dangerous fault. Geologists estimate that the southern San Andreas could produce a quake of up to magnitude 8.3. As far as they know, the fault hasn't ever produced a quake larger than the 1857 or 1906 quakes, both of which were probably around magnitude 7.9. That is plenty destructive, though. The magnitude 6.9 Loma Prieta earthquake that hit the Bay Area in 1989 killed 63 people. And remember that earthquake magnitude goes up by 10 for every whole number, so a magnitude 8.3 would be more than 25 times bigger than the Loma Prieta quake. If a magnitude 7.8 quake were to hit the southern San Andreas, geologists expect it would cause 1,800 deaths, 50,000 injuries and $200 billion in damage. Scientists can't predict when the next San Andreas earthquake — or any earthquake — will occur. But they can get an idea of the future risk by looking at how often earthquakes have occurred in the past. On the southern San Andreas, some sections seem to give off a good shake every 100 years or so, while others go as long as 300 years between major quakes. The Fort Tejon area, about 70 miles (113 km) north of Los Angeles, typically sees a large quake every 100 to 150 years. The last time it had a large earthquake was in 1857, so that area is considered overdue. The average time between earthquakes depends on the fault or section of the not always the same; they can vary by years or decades. Also, dangerous quakes can happen on side faults that scientists don't even know about. The magnitude 6.7 Northridge earthquake that struck Los Angeles in 1994 happened on a fault geologists previously didn't know existed. This fault wasn't part of the San Andreas, but it was a nearby fault affected by the San Andreas' motion. The U.S. Geological Survey, which tracks faults and measures earthquakes, has calculated that there's a 72% chance of a magnitude 6.7 earthquake in the San Francisco Bay region by 2043. And there's a 60% chance of a quake of 6.7 or larger in that time frame in the Los Angeles region. Image 1 of 5 One of the easiest places to see the San Andreas Fault is in the Coachella Valley of Southern California. The fault line is the narrow valley between the two white arrows, and the wrinkled landscape reveals how the movement of the plates creates hills and troughs. Image 2 of 5 The San Andreas Fault becomes complicated and branching in the San Gorgonio Pass north of Palm Springs, California. The white arrows in this image show one of the fault lines shaping this region. Image 3 of 5 The San Andreas Fault runs through Cajon Pass in California, which is a major artery for train and vehicle travel. Image 4 of 5 The 1989 Loma Prieta earthquake caused serious damage in the San Francisco Bay Area. This photo shows a car crushed under the third floor of an apartment building in the city's Marina district. The ground liquefied due to the shaking, causing the first two floors to sink and collapse. Image 5 of 5 The Hayward Fault, part of the San Andreas Fault system, runs directly through the University of California, Berkeley football stadium. Why can earthquakes happen far from plate boundaries? The 20 largest recorded earthquakes in history Nearly 75% of the U.S. is at risk from damaging earthquakes
Yahoo
15-05-2025
- Science
- Yahoo
Scientist Issues Warning of Major West Coast Earthquake
It's been nearly 12 decades since the Great San Francisco Earthquake of 1906 killed as many as 3,000 people. Now, one scientist is warning that another major West Coast earthquake could be imminent and perhaps even more devastating than that one. Tina Dura, a geosciences professor at Virginia Tech, was the lead author of a recent study that looked into the risk of major flooding in Washington, Oregon, and Northern California. The study looked into flooding that would be caused from two factors happening together: powerful earthquakes and rising sea levels due to climate change. Dura and other experts have begun to worry about "the next big event being imminent" in the Cascadia subduction zone, which stretches from Northern California to Washington, given that a major event has not happened in over 300 years. "We expect something like the Japan 2011 and Sumatra 2004 earthquakes and tsunamis to occur there," Dura told Accuweather. In an email to Newsweek, Dura clarified that such an earthquake could come "tomorrow or decades from now," but it's "well within the window of possibility." "But geologically speaking, we're well within the window of possibility. The last event was in 1700, and paleoseismic records show these earthquakes recur roughly every 200 to 800 years," she told Newsweek. "The National Seismic Hazard model shows that there is a 15% chance of a large (over magnitude 8) earthquake happening sometime in the next 50 years. "By 2100, there is a 30% chance of a large earthquake happening. To me, those probabilities are high enough that we should be preparing for the effects of such an earthquake." The Cascadia Subduction Zone is a fault line where the Juan de Fuca tectonic plate is slowly sliding beneath the North American plate. As Newsweek explains, the boundary between the two tectonic plates is capable of producing megathrust earthquakes that strike with little warning, impacting hundreds of miles of coastline simultaneously, which could trigger widespread land subsidence, powerful tsunamis, and long-lasting infrastructure failures. Based on the warnings from Dura and other experts, it sounds like this type of earthquake could strike at any time.
Yahoo
19-04-2025
- Yahoo
Three dead, three injured in Marin County crash
(KRON) — Three people are dead and three more are hospitalized with serious injuries after a Volkswagen Tiguan hit a tree on San Geronimo Valley Road just west of Sir Francis Drake Boulevard shortly before 7:30 p.m. Friday, according to the California Highway Patrol. For reasons unknown, the SUV crashed into a tree and became engulfed in flames. Good Samaritans were on scene and attempted to free some of the people inside the burning SUV. Prediction of 'major earthquake' on anniversary of Great San Francisco Earthquake not credible, experts say CHP is still investigating the cause of the single-vehicle crash. No other details are available about the crash at this time. Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
Yahoo
19-04-2025
- Yahoo
Tool thief brandished gun at East Bay Home Depot: Police
SAN FRANCISCO (KRON) — An Oakland man was arrested after he allegedly stole multiple power tools from a Newark Home Depot and brandished a gun at a bystander filming the theft in the store parking lot, Newark police said. The alleged theft occurred shortly before 8 p.m. Wednesday. 'Upon arrival, officers gathered information indicating that the suspect had stolen merchandise from the store,' the Newark Police Department said. 'A good Samaritan attempted to document the incident on video as the suspect loaded the stolen power tools into his getaway car. The suspect responded by threatening the witness with a handgun.' Victim named, suspect arrested in Concord murder case The suspect did not physically harm the bystander filming the crime, authorities said. Information provided by the witness was later used to identify the suspect. The suspect was identified as 34-year-old Samuel Grajales. The Southern Alameda County Major Crimes Task Force located the getaway vehicle and the suspect hours later. Grajales was arrested and the stolen power tools were recovered from the suspect's vehicle. Grajales was arrested for shoplifting, brandishing a firearm in public. and for outstanding warrants. Grajales' case was referred to the Alameda County District Attorney's Office for prosecution. Prediction of 'major earthquake' on anniversary of Great San Francisco Earthquake not credible, experts say 'We extend our sincere gratitude to the vigilant witness whose quick action helped lead to the swift apprehension of a dangerous individual,' the Newark Police Department said. 'We encourage everyone to remain observant and report any suspicious activity. Remember: if you see something, say something. Please consider your safety first, before attempting to confront or intervene with a suspect, and do not hesitate to call 911 when witnessing a crime.' Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
Yahoo
19-04-2025
- Yahoo
Victim named, suspect arrested in Concord murder case
SAN FRANCISCO (KRON) — The Concord Police Department has identified the man who was shot and killed near the intersection of Monument Boulevard and Reganti Drive in Concord on April 14 at approximately 3 a.m. A suspect was also arrested in the case. The victim of the shooting was identified as 40-year-old Omar Garcia. Garcia was pronounced dead at the scene. Prediction of 'major earthquake' on anniversary of Great San Francisco Earthquake not credible, experts say Concord Police Department detectives identified 27-year-old Chance Martin of Pittsburg, Calif. as the murder suspect. CPD, the U.S. Marshals Service Fugitive Apprehension Task Force, and the Pleasant Hill and Antioch police departments, served search warrants in Pleasant Hill and Antioch. During the searches, authorities found and arrested Martin, who was later booked into the Martinez Detention Facility. High school football player dies following weekend diving accident at Stinson Beach 'It is believed that Martin had been involved in a dispute in the parking lot of 1500 Monument Blvd. with a group of males, had left in a vehicle, and then returned a short time later and shot multiple times from the window of his vehicle at the group of people with whom he had previously been arguing,' CPD said. 'One of the bullets he fired struck and killed Garcia.' Martin faces murder charges and will remain in custody. Anyone with additional information about the shooting is asked to contact Concord police. Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
