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61-615: Tejon Pass marks the intersection of the two largest seismic faults in California; the San Andreas and Garlock fault systems. The highest point of the pass is near the northwesternmost corner of Los Angeles County , north of Gorman . Its elevation is 4,160 feet (1,270 m) along Peace Valley Road and Gorman Post Road, 70 miles (110 km) northwest of downtown Los Angeles and 46 miles (74 km) south of Bakersfield . Interstate 5 , which connects Southern California with

122-617: A spreading center between the Pacific plate and the Farallon plate (which is now mostly subducted, with remnants including the Juan de Fuca plate , Rivera plate , Cocos plate , and the Nazca plate ) was beginning to reach the subduction zone off the western coast of North America. As the relative motion between the Pacific and North American plates was different from the relative motion between

183-590: A different degree of earthquake risk. The average slip rate along the entire fault ranges from 20 to 35 mm (0.79 to 1.38 in) per year. In the north, the fault terminates offshore near Eureka, California , at the Mendocino triple junction , where three tectonic plates meet. The Cascadia subduction zone intersects the San Andreas fault at the Mendocino triple junction. It has been hypothesized that

244-727: A different section of land than the first. With the cession of California to the United States following the Mexican-American War , the 1848 Treaty of Guadalupe Hidalgo provided that the land grants would be honored. As required by the Land Act of 1851, a claim for Rancho Los Álamos y Agua Caliente was filed with the Public Land Commission in 1852, The grant was patented to Agustín Olvera , Louis Jordan, and J.L. Brent in 1866. A separate claim

305-560: A link between the water level in Lake Cahuilla (now the Salton Sea ) and seismic activity along the southern San Andreas Fault. The study suggests that major earthquakes along this section of the fault coincided with high water levels in the lake. The hydrological load caused by high water levels can more than double the stress on the southern San Andreas Fault, which is likely sufficient for triggering earthquakes. This may explain

366-563: A magnitude 7.8 earthquake along the southern San Andreas Fault could cause about 1,800 deaths and $ 213 billion in damage. This scenario hypothesizes the potential effects of a 7.0 magnitude earthquake on the San Andreas Fault in the San Francisco Bay Area. It aims to estimate the impacts on urban infrastructures along with the rebuilding efforts to both the landscape and economy. This study combines not only

427-537: A major earthquake along the Cascadia subduction zone could trigger a rupture along the San Andreas Fault. In the south, the fault terminates near Bombay Beach, California , in the Salton Sea . Here, the plate motion is being reorganized from right-lateral to divergent . In this region (known as the Salton Trough ), the plate boundary has been rifting and pulling apart, creating a new mid-ocean ridge that

488-715: A portion of the fault is easily examined at a roadcut for the Antelope Valley Freeway . The fault continues northwest alongside the Elizabeth Lake Road to the town of Elizabeth Lake . As it passes the towns of Gorman , Tejon Pass and Frazier Park , the fault begins to bend northward, forming the "Big Bend". This restraining bend is thought to be where the fault locks up in Southern California , with an earthquake-recurrence interval of roughly 140–160 years. Northwest of Frazier Park,

549-499: Is a combined effort from experts in the physical sciences, social sciences, and engineering both in the public and private sectors- ranging from urban planners to economists/business professionals. Not only does this study aim to estimate the impacts of the event, but aims to estimate the years of rebuilding and funding needed to recover communities from a potential disaster such as the HayWired Scenario. The first volume of

610-543: Is a continental right-lateral strike-slip transform fault that extends roughly 1,200 kilometers (750 mi) through the U.S. state of California . It forms part of the tectonic boundary between the Pacific plate and the North American plate . Traditionally, for scientific purposes, the fault has been classified into three main segments (northern, central, and southern), each with different characteristics and

671-607: Is an extension of the Gulf of California . Sediment deposited by the Colorado River is preventing the trough from being filled in with sea water from the gulf. The fault was first identified in 1895 by Professor Andrew Lawson of UC Berkeley . In the wake of the 1906 San Francisco earthquake , Lawson was tasked with deciphering the origin of the earthquake. He began by surveying and mapping offsets (such as fences or roads that had been sliced in half) along surface ruptures. When

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732-527: Is sometimes closed by the California Highway Patrol , generally because of the icy conditions combined with the steep grade of the pass, and the high traffic during the winter holidays. The Highway Patrol is also concerned, especially with the number of big-rigs that pass through, that one accident in the snowy conditions might force traffic to slow down or come to a complete stop, leaving hundreds of vehicles stalled at once. Whenever there

793-724: Is such a closure, traffic must either wait for it to reopen, or endure a multi-hour detour. This historic gap has given its name to the Mountain Communities of the Tejon Pass . Beginning on the south at Santa Clarita , it passes through Castaic , Gorman , and Lebec , to end at Grapevine . It passes by the Tejon Ranch , where two large planned communities — Centennial and Tejon Mountain Village —are proposed. San Andreas Fault The San Andreas Fault

854-411: Is that Lawson named the fault after this lake. However, according to some of his reports from 1895 and 1908, he actually named it after the surrounding San Andreas Valley. Following the 1906 San Francisco earthquake, Lawson also concluded that the fault extended all the way into Southern California . In 1953, geologist Thomas Dibblee concluded that hundreds of miles of lateral movement could occur along

915-420: The 1994 Northridge earthquake ) occurs about once every 6.7 years statewide. The same report also estimated there is a 7% probability that an earthquake of magnitude 8.0 or greater will occur in the next 30 years somewhere along the San Andreas Fault. A different USGS study in 2008 tried to assess the physical, social and economic consequences of a major earthquake in southern California. That study predicted that

976-619: The Salton Sea , contains upturned strata associated with that section of the fault. The fault then runs along the southern base of the San Bernardino Mountains , crosses through Cajon Pass and continues northwest along the northern base of the San Gabriel Mountains . These mountains are a result of movement along the San Andreas Fault and are commonly called the Transverse Range. In Palmdale ,

1037-594: The San Joaquin Valley and the north, reaches its highest point in the state, 4,144 feet (1,263 m), near the summit of Tejon Pass. The pass has a gradual rise from its southern approach of 1,362 feet (415 m) at Santa Clarita , but a precipitous descent through Grapevine Canyon toward the San Joaquin Valley on the north, where it ends at Grapevine at 1,499 feet (457 m). On its northward slope lies Fort Tejon State Historic Park ,

1098-645: The Santa Cruz Mountains , epicenter of the 1989 Loma Prieta earthquake , then up the San Francisco Peninsula , where it was first identified by Professor Lawson in 1895, then offshore at Daly City near Mussel Rock . This is the approximate location of the epicenter of the 1906 San Francisco earthquake . The fault returns onshore at Bolinas Lagoon just north of Stinson Beach in Marin County . It returns underwater through

1159-815: The Tehachapi Mountains , Rancho El Tejon and Rancho Castac . The rancho is now a part of the 270,000 acres (1,093 km ) Tejon Ranch . A grant was made to Pedro Carrillo by Governor Manuel Micheltorena in 1843, that included Hungry Valley , Cañada de los Alamos and Peace Valley , the later area of the Hungry Valley State Vehicular Recreation Area , Gorman and the Tejon Pass (then called Portezuela de Castac or Castac Pass), but Carrillo failed to comply with any of its conditions. In 1846, Governor Pío Pico declared that, "Taking into consideration

1220-526: The U.S. Geological Survey (USGS) have made variable predictions as to the risk of future seismic events. The ability to predict major earthquakes with sufficient precision to warrant increased precautions has remained elusive. The U.S. Geological Survey's most recent forecast, known as UCERF3 (Uniform California Earthquake Rupture Forecast 3), released in November 2013, estimated that an earthquake of magnitude 6.7 M or greater (i.e. equal to or greater than

1281-548: The eastern California shear zone . This complicated evolution, especially along the southern segment, is mostly caused by either the "Big Bend" and/or a difference in the motion vector between the plates and the trend of the fault and its surrounding branches. The fault was first identified in Northern California by UC Berkeley geology professor Andrew Lawson in 1895 and named by him after the surrounding San Andreas valley. Eleven years later, Lawson discovered that

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1342-613: The Antelope Valley, over this original Tejon Pass, and down into Tejon Canyon, and then proceeded west along Tejon Creek—into the lands of the Rancho Tejon , that had been granted in 1843. This route to the pass diverted from the El Camino Viejo at Elisabeth Lake, and from 1849 to before 1854 it was the main road connecting the southern part of the state to the trail along the eastern side of the San Joaquin Valley to

1403-587: The California economy within the first 6 months post-recovery from the event through estimates of "utility outages, property damages, and supply chain disruptions resulting in an estimated $ 44 billion of gross state product (GSP) losses, or translated at 4% of the California economy"(Wein et al.). This study also projects the recovery of jobs lost in highly impacted areas, such as Alameda County, could take up to 10 years to fully recover job losses and possible economic recession. Trajectories for economic recovery are improved by reconstruction but also delayed with impacts to

1464-465: The Cañada de las Uvas) and then descended San Emigdio Creek into the San Joaquin Valley. In 1806, Father Jose Maria Zalvidea, diarist for the expedition of First Lieutenant Francisco Ruiz into the San Joaquin Valley, named the canyon, creek, and pass which had been discovered in 1776 by the explorer priest, Father Francisco Garces . He recorded the name as "Tejon" (badger)—after a dead badger found at

1525-687: The Farallon and North American plates, the spreading ridge began to be "subducted", creating a new relative motion and a new style of deformation along the plate boundaries. These geological features are what are chiefly seen along San Andreas Fault. It also includes a possible driver for the deformation of the Basin and Range , separation of the Baja California peninsula , and rotation of the Transverse Range . The main southern section of

1586-661: The HayWired Scenario study was released in 2017, with consistent continuations and contributions by engineers. This continuation was published in the second volume, Engineering Implications, in 2018. As of the 2021 Fact sheet update, there are several estimates on damages ranging from the approximate people affected at home, work, effects of lifeline infrastructures such as telecommunications, and more. This group of scientists have worked together to create estimates of how hazards such as liquefaction, landslides, and fire ignition will impact access to utilities, transportation, and general emergency services. This study goes into detail about

1647-689: The North American plate has forced the San Andreas to jog westward. This has led to the formation of the Transverse Ranges in Southern California, and to a lesser but still significant extent, the Santa Cruz Mountains (the location of the Loma Prieta earthquake in 1989). Studies of the relative motions of the Pacific and North American plates have shown that only about 75 percent of the motion can be accounted for in

1708-466: The San Andreas Fault near Parkfield in central California consistently produces a magnitude 6.0 earthquake approximately once every 22 years. Following recorded seismic events in 1857, 1881, 1901, 1922, 1934, and 1966, scientists predicted that another earthquake should occur in Parkfield in 1993. It eventually occurred in 2004 . Due to the frequency of predictable activity, Parkfield has become one of

1769-475: The San Andreas Fault proper has only existed for about 5 million years. The first known incarnation of the southern part of the fault was Clemens Well-Fenner- San Francisquito fault zone around 22–13 Ma. This system added the San Gabriel Fault as a primary focus of movement between 10–5 Ma. Currently, it is believed that the modern San Andreas will eventually transfer its motion toward a fault within

1830-422: The San Andreas Fault stretched southward into southern California after reviewing the effects of the 1906 San Francisco earthquake . Large-scale (hundreds of miles) lateral movement along the fault was first proposed in a 1953 paper by geologists Mason Hill and Thomas Dibblee . This idea, which was considered radical at the time, has since been vindicated by modern plate tectonics . Seismologists discovered that

1891-463: The San Andreas fault has reached a sufficient stress level for an earthquake of magnitude greater than 7.0 on the moment magnitude scale to occur. This study also found that the risk of a large earthquake may be increasing more rapidly than scientists had previously believed. Moreover, the risk is currently concentrated on the southern section of the fault, i.e. the region around Los Angeles, because strong earthquakes have occurred relatively recently on

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1952-517: The San Andreas towards Walker Lane. Assuming the plate boundary does not change as hypothesized, projected motion indicates that the landmass west of the San Andreas Fault, including Los Angeles, will eventually slide past San Francisco, then continue northwestward toward the Aleutian Trench , over a period of perhaps twenty million years. The San Andreas began to form in the mid- Cenozoic about 30 Mya (million years ago). At this time,

2013-578: The abnormally long period of time since the last major earthquake in the region since the lake has dried up. The San Andreas Fault System has been the subject of a flood of studies. In particular, scientific research performed during the last 23 years has given rise to about 3,400 publications. A study published in 2006 in the journal Nature by Yuri Fialko, an associate professor at the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics at Scripps Institution of Oceanography , found that

2074-692: The canyon beyond the pass leading down into the Tulare Basin, Cañada de las Uvas (Canyon of the Grapes) for all the wild California grape vines ( Vitis californica ) growing in it. In the late 18th century, El Camino Viejo , a road between Los Angeles and the Mission Santa Clara de Asis began to be used for travel north and south along the western San Joaquin Valley. It crossed over the pass and turned westward up Cuddy Canyon , (avoiding

2135-618: The canyon's mouth. This original Tejon Pass (later called "Old Tejon Pass"), is situated 15 miles to the northeast of what is now Tejon Pass. The old pass goes through the Tehachapi Mountains, at the top of the divide between Tejon Creek Canyon in the San Joaquin Valley and Cottonwood Creek Canyon in Antelope Valley . Before 1854, the main route of travel into the San Joaquin Valley had come directly north from Elizabeth Lake (originally Laguna de Chico Lopez ) across

2196-1194: The central ( 1857 ) and northern ( 1906 ) segments of the fault, while the southern section has not seen any similar rupture for at least 300 years. According to this study, a major earthquake on that southern section of the San Andreas fault would result in major damage to the Palm Springs – Indio metropolitan area and other cities in San Bernardino , Riverside and Imperial counties in California, and Mexicali Municipality in Baja California . It would be strongly felt (and potentially cause significant damage) throughout much of Southern California , including densely populated areas of Los Angeles County , Ventura County , Orange County , San Diego County , Ensenada Municipality and Tijuana Municipality , Baja California, San Luis Rio Colorado in Sonora and Yuma, Arizona . Older buildings would be especially prone to damage or collapse, as would buildings built on unconsolidated gravel or in coastal areas where water tables are high (and thus subject to soil liquefaction ). Of

2257-467: The construction industry. A 2008 paper, studying past earthquakes along the Pacific coastal zone, found a correlation in time between seismic events on the northern San Andreas Fault and the southern part of the Cascadia subduction zone (which stretches from Vancouver Island to Northern California). Scientists believe quakes on the Cascadia subduction zone may have triggered most of the major quakes on

2318-569: The crest of the Tejon Pass), as "one of the oldest continuously used roadside rest stops in California." This is because pre-Columbian indigenous Californians "would have stopped there when it was the Tataviam village of Kulshra'jek", a trading crossroads for hundreds to thousands of years. In 1772, Lieutenant Pedro Fages crossed the pass in pursuit of military deserters, and named it Portezuelo de Cortes (Cortes Pass). Fages also named

2379-412: The equivalent of eight complete circles," according to R.M. Gillis of Fresno, District 6 highways engineer. Bears roam the rugged area. The pass is sunny in summer, spring, and autumn, but is subject to severe weather and closure to traffic in winter. Car engines frequently overheat when ascending the long grade, especially in hot weather. The 40-mile stretch of Interstate 5 between Grapevine and Castaic

2440-540: The fault runs through the Carrizo Plain , a long, treeless plain where much of the fault is plainly visible. The Elkhorn Scarp defines the fault trace along much of its length within the plain. The southern segment, which stretches from Parkfield in Monterey County all the way to the Salton Sea , is capable of an 8.1-magnitude earthquake. At its closest, this fault passes about 35 miles (56 km) to

2501-494: The fault. A National Science Foundation funded project called the San Andreas Fault Observatory at Depth (SAFOD) near Parkfield, California , involved drilling through the fault from 2004 to 2007. The aim was to collect core samples and make direct geophysical and geochemical observations to better understand fault behavior at depth. The northern segment of the fault runs from Hollister , through

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2562-433: The geological impacts/effects of the event, but also the societal impacts such as property damage, economic rebuilding, and aims at estimating damages if cities increased risk-reduction. It was developed for preparedness geared towards Bay Area residents and as a warning with an attempt to encourage local policy makers to create infrastructure and protections that would further risk reduction and resilience-building. This study

2623-606: The goldfields to the north. In 1843, Rancho Castac was established in La Cañada de las Uvas. During that same year, the first grant of Rancho Los Alamos y Agua Caliente included the pass, which was now called Portezuela de Castac (Castaic Pass). After the establishment of Fort Tejon and the Stockton - Los Angeles Road , the Portezuela de Castac began to be called the "Fort Tejon Pass." The rather poor wagon route of

2684-615: The horses were changed. Six of them were used for the pull up from Bakersfield to Gorman's. The Ridge Route was the first automobile highway linking the Central Valley with the Los Angeles Basin . It was laid in a sinuous fashion through the ridges and gullies of the Sierra Pelona Mountains to the Tejon Pass around 1910. The northern portion of this highway, which became a part of U.S. Route 99 ,

2745-523: The influence of plate tectonics . The rate of slippage averages about 33 to 37 millimeters (1.3 to 1.5 in) a year across California. The southwestward motion of the North American plate towards the Pacific is creating compressional forces along the eastern side of the fault. The effect is expressed as the Coast Ranges. The northwest movement of the Pacific plate is also creating significant compressional forces which are especially pronounced where

2806-547: The linear trough of Tomales Bay which separates the Point Reyes Peninsula from the mainland, runs just east of Bodega Head through Bodega Bay and back underwater, returning onshore at Fort Ross . (In this region around the San Francisco Bay Area several significant "sister faults" run more-or-less parallel, and each of these can create significantly destructive earthquakes.) From Fort Ross,

2867-422: The location of these offsets were plotted on a map, he noted that they made a near perfect line on top of the fault he previously discovered. He concluded that the fault must have been the origin of the earthquake. This line ran through San Andreas Lake , a sag pond . The lake was created from an extensional step over in the fault, which created a natural depression where water could settle. A common misconception

2928-459: The most important areas in the world for large earthquake research. In 2004, work began just north of Parkfield on the San Andreas Fault Observatory at Depth (SAFOD). The goal of SAFOD is to drill a hole nearly 3 kilometres (1.9 mi) into the Earth's crust and into the San Andreas Fault. An array of sensors will be installed to record earthquakes that happen near this area. A 2023 study found

2989-627: The movements of the San Andreas and its various branch faults. The rest of the motion has been found in an area east of the Sierra Nevada mountains called the Walker Lane or Eastern California Shear Zone. The reason for this is not clear. Several hypotheses have been offered and research is ongoing. One hypothesis – which gained interest following the Landers earthquake in 1992 – suggests the plate boundary may be shifting eastward away from

3050-481: The northeast of Los Angeles. Such a large earthquake on this southern segment would kill thousands of people in Los Angeles, San Bernardino, Riverside, and surrounding areas, and cause hundreds of billions of dollars in damage. The Pacific plate , to the west of the fault, is moving in a northwest direction while the North American plate to the east is moving toward the southwest, but relatively southeast under

3111-539: The northern San Andreas within the past 3,000 years. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. However the 1906 San Francisco earthquake seems to have been the exception to this correlation because the plate movement was mostly from south to north and it was not preceded by a major quake in the Cascadia zone. The San Andreas Fault has had some notable earthquakes in historic times: Rancho Los Alamos y Agua Caliente Rancho Los Álamos y Agua Caliente

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3172-497: The northern segment continues overland, forming in part a linear valley through which the Gualala River flows. It goes back offshore at Point Arena . After that, it runs underwater along the coast until it nears Cape Mendocino , where it begins to bend to the west, terminating at the Mendocino triple junction . The central segment of the San Andreas Fault runs in a northwestern direction from Parkfield to Hollister . While

3233-679: The old Tejon Pass route was generally abandoned, and eventually the Fort Tejon Pass took the shortened name it has today. In 1858 the Butterfield Overland Mail stagecoach line ran through the pass on the Stockton - Los Angeles Road. The Butterfield Overland was discontinued in 1861 but was replaced by the Telegraph Stage Line, which stopped at almost all the former stations, including Gorman's, where

3294-423: The roadway to avoid hitting oncoming automobiles. He died when the truck burst into flames. The curve (in adjoining photo) was eliminated in 1935 with improvements completed from Fort Tejon to Grapevine station. That work "supersedes the worst portions of the old twenty-foot Grapevine Canyon Highway, shortens the length of the road by approximately eight-tenths of a mile and eliminates 2,937 degrees of curvature or

3355-445: The seven months granted to citizen Pedro Carrillo to stock the land granted to him in conformity with the colonization laws, and of the injury caused to the industry of the country on account of his not occupying it, the denunciation of the tract of the Álamos and Agua Caliente in favor of the applicants may take place, to whom the proper title shall be issued," and on the same day a title was issued to Agustín Olvera . This grant covered

3416-612: The site of a former U.S. Army post, first garrisoned on August 10, 1854. The pass actually crosses 3 mountain ranges. The stretch from Lake Hughes Road to State Route 138 crosses the Sierra Pelona Mountains , and goes through the Angeles National Forest and the section from SR 138 to Grapevine crosses the Tehachapis and the San Emigdios. Historians speak of the area around Gorman, California (just south of

3477-455: The southern section of the fault and the parts through Parkfield experience earthquakes, the rest of the central section of the fault exhibits a phenomenon called aseismic creep , where the fault slips continuously without causing earthquakes. It was formed by a transform boundary. The southern segment (also known as the Mojave segment) begins near Bombay Beach, California . Box Canyon, near

3538-526: The specific populations to be hardest impacted by a potential earthquake of a 7.0 magnitude, specifically in the San Francisco Bay Area. This includes intensified hardships for those with low-income, racially and culturally-diverse populations, and people with literacy hardships that would significantly "increase their risk of displacement and add to recovery challenges" (Wein et al.). In addition to societal and landscape impacts, this study looks at potential business interruptions. This portion estimates impacts to

3599-412: The study, Fialko stated: All these data suggest that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell. It could be tomorrow or it could be 10 years or more from now. Nevertheless, in the 18 years since that publication there has not been a substantial quake in the Los Angeles area, and two major reports issued by

3660-485: Was a 26,626-acre (107.75 km ) Mexican land grant in present-day Kern County, California given in 1846 by Governor Pio Pico to Francisco Lopes, Luis Jordan and Vicente Botiller. The name means "Cottonwoods and Hot Springs Ranch" in Spanish. The native riparian Fremont Cottonwood (Populus fremontii) grow around natural springs . Rancho Los Álamos y Agua Caliente lay between two other Mexican Land Grants in

3721-422: Was known as " The Grapevine ." The Ridge Route was replaced by a three-lane alternate highway in 1933, a four-lane expressway in 1947, and later by the eight-lane Interstate 5 Freeway in 1970. A section of the highway known as "Dead Man's Curve," was the "scene of many accidents on the narrow old road," and in July 1932 it took the life of Jack Klieby, 33, who deliberately drove his truck, transporting gasoline, off

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