{"id":360270,"date":"2026-06-14T11:33:24","date_gmt":"2026-06-14T11:33:24","guid":{"rendered":"https:\/\/www.newsbeep.com\/us-ca\/360270\/"},"modified":"2026-06-14T11:33:24","modified_gmt":"2026-06-14T11:33:24","slug":"san-andreas-fault-stress-hits-1000-year-high-raising-quake-risk","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us-ca\/360270\/","title":{"rendered":"San Andreas Fault stress hits 1,000-year high, raising quake risk"},"content":{"rendered":"

Tectonic stress along Southern California\u2019s San Andreas and San Jacinto fault systems<\/a> has reached \u2014 and in some areas exceeded \u2014 the highest levels seen in the past 1,000 years, according to new research led by Earth scientists at the University of Hawai\u02bbi at M\u0101noa<\/a>.<\/p>\n

Researchers say the system is not showing signs of an imminent rupture, but is operating under unusually high stress in a long-term seismic cycle that could support large earthquakes, including multi-fault events.<\/p>\n

The study, published in the Journal of Geophysical Research: Solid Earth<\/a>, suggests the region is in a \u201ccritically loaded state,\u201d with stress building across multiple fault segments. One key area of focus is Cajon Pass, a junction between the two fault systems that may act as an \u201cearthquake gate,\u201d either blocking ruptures from crossing between faults or allowing them to link into a single larger event.<\/p>\n

Lead author Liliane Burkhard, a research affiliate at the University of Hawai\u02bbi\u2019s Institute of Geophysics and Planetology and scientist at the University of Bern, said the system is highly stressed after more than 160 years since the last major rupture.<\/p>\n

\u201cRight now, with stress at historically high levels across the region and more than 160 years elapsed since the last major rupture, the system is in a critically loaded state,\u201d Burkhard said.<\/p>\n

Researchers say a rupture involving both fault systems could be significantly more damaging than a single-fault earthquake due to its size and proximity to major population centers, including Los Angeles, San Bernardino, Riverside, and the Coachella Valley.<\/p>\n

More: El Nin\u0303o will be very bad for the economy. Here’s why<\/a><\/p>\n

Can the San Andreas Fault fully break?<\/p>\n

The San Andreas Fault is not a crack that can \u201csplit open\u201d and drop a chunk of California away from the continent. It\u2019s a strike-slip plate boundary, meaning the Pacific Plate and North American Plate are sliding past each other horizontally, not pulling apart, according to the U.S. Geological Survey<\/a>.<\/p>\n

So even in a very large earthquake, what happens is sideways movement along the fault, not a breakup of the landmass. Parts of California can shift suddenly by feet or even tens of feet during a major rupture, but both sides remain part of the same crustal system.<\/p>\n

There are other tectonic settings on Earth where continents rift apart and eventually form new oceans \u2014 such as the East African Rift, which is in the process of splitting into two tectonic plates \u2014 but the San Andreas system is not one of them. It is a strike-slip boundary, where plates slide past each other rather than spreading apart.<\/p>\n

However, over millions of years, continued movement along the fault could gradually bring Los Angeles and San Francisco into closer proximity, geologic models suggest<\/a>.<\/p>\n

What would happen if the San Andreas Fault ruptured?<\/p>\n

Surface rupture occurs when movement along a fault deep within the Earth breaks through to the surface. According to the Pacific Northwest Seismic Network<\/a>, it is one of the clearest physical expressions of an earthquake, showing permanent deformation where two sides of a fault slip past one another.<\/p>\n

Most earthquakes do not produce surface rupture, according to the U.S. Geological Survey<\/a>. Some faults do not reach the surface, and even when they do, rupture does not always propagate all the way upward during a given event.<\/p>\n

When surface rupture occurs, it can produce either horizontal or vertical offsets, depending on the type of fault. Strike-slip faults, such as the San Andreas Fault, typically cause horizontal displacement, whereas dip-slip faults can produce vertical displacement. Some earthquakes involve a combination of both.<\/p>\n

In a major rupture, strong shaking could last tens of seconds to more than a minute. The most severe damage would occur near the fault and in areas built on soft or water-saturated soils, which can amplify shaking and increase the risk of liquefaction. Scientists note that infrastructure built across active faults is especially vulnerable, as surface rupture can directly offset roads, buildings, and other structures that span the fault trace.<\/p>\n

More: Storm rips roof off Illinois animal shelter, displacing 100+ animals<\/a><\/p>\n

San Andreas Fault map\"The<\/p>\n

The San Andreas Fault runs through California, forming the major boundary between the Pacific Plate and the North American Plate.<\/p>\n

What causes earthquakes?<\/p>\n

The Earth has four layers: the\u00a0inner core, outer core, mantle,\u00a0and\u00a0crust. The crust and top of the mantle make up another area called the “lithosphere<\/a>,” which acts like a skin surrounding the Earth’s surface.<\/p>\n

The lithosphere, however, is not a single piece but is divided into puzzle-like fragments called tectonic plates, according to the USGS. These parts of the lithosphere are not stationary and move slowly.<\/p>\n

As tectonic plates move past one another, they occasionally bump or collide. This places stress on the plates’ edges. When the stress becomes too great, it creates cracks called “faults.” The point where these faults move against each other is called the “fault line.”<\/p>\n

When there is too much friction between the fault lines, energy is suddenly released, triggering seismic waves that cause an earthquake.<\/p>\n

Why are earthquakes so common in California?<\/p>\n

California sits along the boundary between two massive tectonic plates \u2014 the Pacific Plate and the North American Plate. These plates are constantly moving, sliding past one another at different speeds.<\/p>\n

The state is also home to more than 500 active faults, according to geologists, making it one of the most earthquake-prone regions in the United States. The most famous is the San Andreas Fault, a roughly 800-mile system that runs through much of the state and forms the primary boundary between the two plates.<\/p>\n

Other major fault systems include the Hayward Fault in the Bay Area, the Calaveras Fault in Central California, and the San Jacinto and Elsinore faults in Southern California.<\/p>\n

But earthquakes are not limited to land. Many occur offshore, including near the Mendocino Triple Junction, where the Pacific, North American, and Gorda plates all meet. That junction creates one of the most seismically active offshore regions along the West Coast.<\/p>\n

Can earthquakes be predicted?<\/p>\n

Earthquakes are not predicted. Neither the U.S. Geological Survey <\/a>nor scientists have predicted a major earthquake, and there’s no expectation that this will change in the near future.<\/p>\n

What is California’s Earthquake Early Warning system?<\/p>\n

California\u2019s Earthquake Early Warning system uses seismic sensors, ground-motion monitoring, and alerting technology to deliver warnings to people via cell phones before the strongest shaking arrives, according to the official website.<\/a><\/p>\n

Officials say even a brief warning can allow people to take protective actions such as \u201cDrop, Cover and Hold On,\u201d or put devices and systems into a safe mode. In some cases, alerts may arrive just as shaking begins or after an earthquake has already passed, particularly for those closer to the epicenter.<\/p>\n

The system is delivered through multiple channels, including Android Earthquake Alerts, Wireless Emergency Alerts, and the MyShake app.<\/p>\n

Developed by the UC Berkeley Seismological Laboratory, MyShake is a free smartphone application that issues audio and visual warnings for earthquakes typically magnitude 4.5 or greater, or when weak shaking is expected. It is available on iPhone and Android devices, as well as select computer platforms.<\/p>\n

Lightning, tornadoes and wild storms: Incredible weather photos<\/p>\n

1 of 55<\/p>\n

A haboob comes into Chandler, Ariz. on Aug. 25, 2025.<\/p>\n

(Patrick Breen\/The Republic)What to do during an earthquake<\/p>\n

Classic evergreen box that pairs well with any quake story.<\/p>\n

Drop to your hands and knees<\/p>\n

Cover your head and neck under sturdy furniture if possible<\/p>\n

Hold on until shaking stops<\/p>\n

Stay indoors unless you are near a known coastal tsunami risk zone<\/p>\n

Stay informed. Get weather alerts via text<\/p>\n

Brandi D. Addison covers weather across the United States as the Weather Connect Reporter for the USA TODAY Network. She can be reached at baddison@gannett.com<\/a>.<\/p>\n

This article originally appeared on USA TODAY: San Andreas Fault at highest stress in 1,000 years and what it means<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Tectonic stress along Southern California\u2019s San Andreas and San Jacinto fault systems has reached \u2014 and in some…\n","protected":false},"author":2,"featured_media":360271,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[31013,7,9,8,3934,146605,146604,146606,146603,56788,14291,101,146117,1009,146602,146114,8955],"class_list":["post-360270","post","type-post","status-publish","format-standard","has-post-thumbnail","category-california","tag-calaveras-fault","tag-california","tag-california-headlines","tag-california-news","tag-earthquakes","tag-fault-systems","tag-north-american-plate","tag-pacific-plate","tag-plate-boundary","tag-san-andreas","tag-san-bernardino","tag-san-francisco","tag-san-jacinto-fault","tag-southern-california","tag-surface-rupture","tag-tectonic-stress","tag-u-s-geological-survey"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/posts\/360270","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/comments?post=360270"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/posts\/360270\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/media\/360271"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/media?parent=360270"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/categories?post=360270"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/tags?post=360270"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}