The earliest known California earthquake was documented in 1769 by the Spanish explorers and Catholic missionaries of the Portolá expedition as they traveled northward from San Diego along the Santa Ana River near the present site of Los Angeles. Ship captains and other explorers also documented earthquakes. As Spanish missions were constructed beginning in the late 18th century, earthquakes records were kept. After the missions were secularized in 1834, records were sparse until the California Gold Rush in the 1840s. From 1850–2004, there was about one potentially damaging event per year on average, though many of these did not cause serious consequences or loss of life.
Since the three damaging earthquakes that occurred in the American Midwest and the East Coast (1755 Cape Ann, 1811–12 New Madrid, 1886 Charleston) were well known, it became apparent to settlers that the earthquake hazard was different in California. While the 1812 San Juan Capistrano, 1857 Fort Tejon, and 1872 Owens Valley shocks were in mostly unpopulated areas and only moderately destructive, the 1868 Hayward event affected the thriving financial hub of the San Francisco Bay Area, with damage from Santa Rosa in the north to Santa Cruz in the south. By this time, scientists were well aware of the threat, but seismology was still in its infancy. Following destructive earthquakes in the late 19th and early 20th centuries, real estate developers, press, and boosters minimized and downplayed the risk of earthquakes out of fear that the ongoing economic boom would be negatively affected.
According to seismologist Charles Richter, the 1906 San Francisco earthquake moved the United States Government into acknowledging the problem. Prior to that, no agency was specifically focused on researching earthquake activity. The United States Weather Bureau did record when they happened and several United States Geological Survey scientists had briefly disengaged from their regular duties of mapping mineral resources to write reports on the New Madrid and Charleston events, but no trained geologists were working on the problem until after 1906 when the Coast and Geodetic Survey was made responsible. The outlook improved when Professor Andrew Lawson brought the state's first monitoring program online at the University of California, Berkeley in 1910 with seismologist Harry Wood, who was later instrumental in getting the Caltech Seismological Laboratory in Pasadena operational in the 1920s.
Early developments at the Caltech lab included an earthquake observation network using their own custom-built short-period seismometers, the Richter magnitude scale, and the Modified Mercalli intensity scale (an updated version of the Mercalli intensity scale). In 1933, the Long Beach earthquake occurred in a populated area and damaged or destroyed many public school buildings in Long Beach and Los Angeles. Some decades later, the San Fernando earthquake affected the San Fernando Valley north of Los Angeles with heavy damage to several hospitals. In both cases, the perception of California policy makers changed, and state laws and building codes were modified (with much debate) to require commercial and residential properties to be built to withstand earthquakes. Higher standards were established for fire stations, hospitals, and schools, and construction of dwellings was also restricted near active faults.
During the last 66 million years, nearly the entire west coast of North America was dominated by a subduction zone, with the Farallon Plate subducting beneath the North American Plate. Presently, the Juan de Fuca Plate (with its Explorer and Gorda satellite plates) and the Rivera and Cocos Plates are the only remnants of the once much larger Farallon Plate. The plate margin that remains in California is that of the strike-slip San Andreas Fault (SAF), the diffuse Pacific–North American plate boundary that extends east into the Basin and Range Province of eastern California and western Nevada (a seismically active area called Walker Lane) and southwest into the California Continental Borderland region off the central and southern coasts. This system of faults terminates in the north at the Mendocino Triple Junction, one of the most seismically active regions in the state, where earthquakes are occasionally the result of intraplate deformation within the Gorda Plate. It terminates in the south at the Salton Sea where displacement transitions to a series of spreading centers and transform faults, beginning with the Brawley Seismic Zone in the Imperial Valley.
In the San Francisco Bay Area, the San Andreas system of faults spans offshore and into the East Bay area, with the bulk of the faults lying to the east of the main SAF. There is a 70% probability that one of these faults will generate a 6.7 Mw or greater earthquake before 2030, including the Hayward Fault Zone, which has gone beyond its average return period of 130 years (154 years ago as of December2022). While the SAF is quiet north of San Francisco , the central SAF segment near San Juan Bautista is where aseismic creep was first studied, and to the south is where the recurring Parkfield earthquakes occur. The secondary faults lay to the west of the main SAF at the extreme southern portion, including the active and young San Jacinto Fault Zone, which may be taking over as the primary boundary south of Cajon Pass. A paleoseismic investigation using Lidar revealed that more than 5 meters (16 ft) of slip has accumulated since the 1857 event on the southern SAF, which borders the Mojave Desert to the north and east of the Greater Los Angeles Area. Near the Transverse Ranges, reverse and thrust faults have produced damaging earthquakes in Santa Barbara and the San Fernando Valley.
|2022-12-20||Humboldt County||North Coast||6.4 Mw||VIII||2||17|
|2014-08-24||South Napa||North Bay||6.0 Mw||VIII||1||~200||$362M–$1bn|
|2014-03-28||La Habra||LA Area||5.1 Mw||VII||Few||$10.8M|
|2010-04-04||Baja California||Baja California||7.2 Mw||VII||2–4||100–233||$1.15bn|
|2010-01-09||Eureka||North Coast||6.5 Mw||VI||35||$21.8–43M|
|2008-07-29||Chino Hills||LA Area||5.4 Mw||VI||8||Limited|
|2007-10-30||Alum Rock||Bay Area||5.6 Mw||VI||Limited|
|2003-12-22||San Simeon||Central Coast||6.6 Mw||VIII||2||40||$250–300M|
|2000-09-03||Yountville||North Bay||5.0 Mw||VII||41||$10–50M|
|1999-10-16||Hector Mine||Eastern||7.1 Mw||VII||4–5||Limited|
|1994-01-17||Northridge||LA Area||6.7 Mw||IX||57||8,700+||$13–40bn|
|1992-06-28||Big Bear||Inland Empire||6.5 Mw||VIII||63||More than $60M||Triggered|
|1992-06-28||Landers||Inland Empire||7.3 Mw||IX||3||400+||$92M|
|1992-04-26||Cape Mendocino||North Coast||6.6 Mw||VIII||Some||Triggered|
|1992-04-26||Cape Mendocino||North Coast||6.5 Mw||VIII||Some||Triggered|
|1992-04-25||Cape Mendocino||North Coast||7.2 Mw||IX||98–356||$48–75M||Tsunami|
|1992-04-22||Joshua Tree||Inland Empire||6.3 Ms||VII||32||Light–moderate|
|1991-06-28||Sierra Madre||LA Area||5.6 Mw||VII||2||100–107||$34–40M|
|1990-02-28||Upland||LA Area||5.7 Mw||VII||30||$12.7M|
|1989-10-17||Loma Prieta||Santa Cruz Mts||6.9 Mw||IX||63||3,757||$5.6–6bn||Tsunami|
|1989-08-08||Loma Prieta||Santa Cruz Mts||5.4 ML||VII||1||Minor|
|1987-11-24||Elmore Ranch||Imperial Valley||6.5 Mw||VIII||2||90+||Triggered|
|1987-11-23||Superstition Hills||Imperial Valley||6.1 Mw||VIII||$3M|
|1987-10-01||Whittier||LA Area||5.9 Mw||VIII||8||200||$213–358M|
|1986-07-21||Chalfant Valley||Eastern||6.2 Mw||VI||2||$2.7M||Sequence|
|1986-07-13||Oceanside||South Coast||5.8 Mw||VI||1||$700k|
|1986-07-08||N. Palm Springs||Inland Empire||6.0 Mw||VII||29–40||$4.5–6M|
|1984-04-24||Morgan Hill||South Bay||6.2 Mw||VIII||21–27||$7.5–8M|
|1983-05-02||Coalinga||Central Valley||6.2 Mw||VIII||94||$10M|
|1981-04-26||Westmorland||Imperial Valley||5.9 Mw||VII||$1–3M|
|1980-11-08||Eureka||North Coast||7.3 Mw||VII||6||$2–2.75M|
|1980-05-25||Mammoth Lakes||Eastern||6.2 Mw||VII||9||$1.5M||Swarm|
|1980-01-26||Livermore||East Bay||5.4 Mw||VII||Doublet|
|1980-01-24||Livermore||East Bay||5.8 Mw||VII||$11.5M||Doublet|
|1979-10-15||Imperial Valley||Imperial Valley||6.4 Mw||IX||91||$30M|
|1979-08-06||Coyote Lake||South Bay||5.7 Mw||VII||16||$500k|
|1978-08-13||Santa Barbara||Central Coast||5.8 Mw||VII||65||$12M|
|1975-08-01||Butte County||Butte County||5.7 ML||VIII||10||$3M|
|1973-02-21||Point Mugu||South Coast||5.8 Mw||VII||Several||$1M|
|1971-02-09||San Fernando||LA Area||6.6 Mw||XI||58–65||200–2,000||$505–553M|
|1969-10-01||Santa Rosa||North Bay||5.7 Mw||VIII||Doublet|
|1969-10-01||Santa Rosa||North Bay||5.6 Mw||VII||1||$8.35M||Doublet|
|1968-04-08||Borrego Mtn||Imperial Valley||6.5 Mw||VII||Some||Rockslides|
|1957-03-22||San Francisco||Bay Area||5.7 Mw||VII||1||40||$1M|
|1954-12-21||Eureka||North Coast||6.5 ML||VII||1||Several||$2.1M|
|1952-08-22||Kern County||Central Valley||5.8 Mw||VIII||2||Several||$10M|
|1952-07-21||Kern County||Central Valley||7.3 Mw||XI||12||Hundreds||$60M|
|1948-12-04||Desert Hot Springs||Inland Empire||6.4 Mw||VII||Several||Minor|
|1941-11-14||Torrance–Gardena||LA Area||5.4 Ms||VIII||$1.1M|
|1941-06-30||Santa Barbara||Central Coast||5.9 Mw||VIII||$100k|
|1940-05-18||El Centro||Imperial Valley||6.9 Mw||X||9||20||$6M|
|1933-03-10||Long Beach||South Coast||6.4 Mw||VIII||115–120||$40M|
|1932-06-06||Eureka||North Coast||6.4 Mw||VIII||1||3||Severe|
|1927-11-04||Lompoc||Central Coast||7.3 Mw||Moderate||Tsunami|
|1925-06-29||Santa Barbara||Central Coast||6.8 Mw||IX||13||$8M|
|1923-01-22||Humboldt County||North Coast||7.2 Ms||Severe||Tsunami|
|1920-06-21||Inglewood||LA Area||4.9 ML||VIII||More than $100k|
|1918-04-21||San Jacinto||Inland Empire||6.7 Mw||IX||1||Several||$200k|
|1915-06-22||Imperial Valley||Imperial Valley||5.5 Mw||VIII||6||$900k||Doublet|
|1906-04-18||San Francisco||Northern–Central||7.9 Mw||XI||700–3,000+||Conflagration / tsunami|
|1899-12-25||San Jacinto||Inland Empire||6.7 Mw||IX||6||$50k or more|
|1898-03-30||Mare Island||North Bay||5.8–6.4 Mw||VIII–IX||$350k|
|1892-04-21||Vacaville–Winters||Central Valley||6.2 MLa||IX||Doublet|
|1892-04-19||Vacaville–Winters||North Bay||6.4 MLa||IX||1||$225–250k||Doublet|
|1892-02-23||Laguna Salada||Baja California||7.1–7.2 Mw||VIII||Moderate|
|1873-11-23||Crescent City||North Coast||6.7 MLa||VIII||Some||Ground cracks|
|1872-03-26||Owens Valley||Eastern||7.4–7.9 Mw||X||27||56||$250k|
|1868-10-21||Hayward||Bay Area||6.3–6.7 Mw||IX||30||$350k|
|1865-10-08||Santa Cruz Mts||Santa Cruz Mts||6.3 MLa||VIII||$500k|
|1857-01-09||Fort Tejon||Central–Southern||7.9 Mw||IX||2||Severe|
|1838-06-??||San Andreas||Bay Area||6.8–7.2 Mw||VIII||Minor|
|1812-12-21||Ventura||Central Coast||7.1 MLa||VIII||1||Tsunami|
|1812-12-08||San Juan Capistrano||South Coast||6.9–7.5||VII–IX||40||Moderate|
| Stover & Coffman 1993 uses various seismic scales. Mla is a local magnitude that is equivalent to ML (Richter magnitude scale) and is used for events that occurred prior to the instrumental period. It is based on the area of perceptibility (as presented on isoseismal maps). Mw = moment magnitude scale and Ms = surface wave magnitude. The inclusion criteria for adding events are based on WikiProject Earthquakes' notability essay that was developed for stand alone articles. The principles described are also applicable to lists. In summary, only damaging, injurious, or deadly events should be recorded. |
k= thousand, M = million, bn = billion
The 1987 Whittier Narrows earthquake occurred in the southern San Gabriel Valley and surrounding communities of Southern California, United States, at 7:42 a.m. PDT on October 1. The moderate magnitude 5.9 blind thrust earthquake was centered several miles north of Whittier in the town of Rosemead, had a relatively shallow depth, and was felt throughout southern California and southern Nevada. Many homes and businesses were affected, along with roadway disruptions, mainly in Los Angeles and Orange counties. Damage estimates ranged from $213–358 million, with 200 injuries, three directly-related deaths, and five additional fatalities that were associated with the event.
The San Jacinto Fault Zone (SJFZ) is a major strike-slip fault zone that runs through San Bernardino, Riverside, San Diego, and Imperial Counties in Southern California. The SJFZ is a component of the larger San Andreas transform system and is considered to be the most seismically active fault zone in the area. Together they relieve the majority of the stress between the Pacific and North American tectonic plates.
The 1868 Hayward earthquake occurred in the San Francisco Bay Area, California, United States on October 21. With an estimated moment magnitude of 6.3–6.7 and a maximum Mercalli intensity of IX (Violent), it was the most recent large earthquake to occur on the Hayward Fault Zone. It caused significant damage and a number of deaths throughout the region, and was known as the "Great San Francisco earthquake" prior to the 1906 San Francisco earthquake and fire.
The 1940 El Centro earthquake occurred at 21:35 Pacific Standard Time on May 18 in the Imperial Valley in southeastern Southern California near the international border of the United States and Mexico. It had a moment magnitude of 6.9 and a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. It was the first major earthquake to be recorded by a strong-motion seismograph located next to a fault rupture. The earthquake was characterized as a typical moderate-sized destructive event with a complex energy release signature. It was the strongest recorded earthquake to hit the Imperial Valley, and caused widespread damage to irrigation systems and led to the deaths of nine people.
The 1948 Desert Hot Springs earthquake occurred on December 4 at 3:43 p.m. Pacific Standard Time with a moment magnitude of 6.4 and a maximum Mercalli intensity of VII. The shock was felt from the central coast of California in the north, and to Baja California in the south, and came at a time when earthquake research in southern California resumed following the Second World War. It was one of two events in the 20th century that have occurred near a complex region of the southern San Andreas Fault system where it traverses the San Gorgonio Pass and the northern Coachella Valley. Damage was not severe, but some serious injuries occurred, and aftershocks continued until 1957.
The 1892 Laguna Salada earthquake occurred at 23:20 Pacific Standard Time on February 23. It had an estimated moment magnitude of 7.1–7.2 and a maximum perceived intensity of VIII (Severe). The shock was centered near the Mexico–United States border and takes its name from a large dry lake bed in Baja California, Mexico. There were no reported casualties, but the event affected the then largely-uninhabited areas of northern Mexico and Southern California.
The 1979 Imperial Valley earthquake occurred at 16:16 Pacific Daylight Time on 15 October just south of the Mexico–United States border. It affected Imperial Valley in Southern California and Mexicali Valley in northern Baja California. The earthquake had a relatively shallow hypocenter and caused property damage in the United States estimated at US$30 million. The irrigation systems in the Imperial Valley were badly affected, but no deaths occurred. It was the largest earthquake to occur in the contiguous United States since the 1971 San Fernando earthquake eight years earlier.
The 1812 San Juan Capistrano earthquake, also known simply as the Capistrano earthquake or the Wrightwood earthquake, occurred on December 8 at 15:00 UTC in Alta California. At the time, this was a colonial territory of the Spanish Empire. Damage occurred at several of the missions in the region of Pueblo de Los Ángeles, including Mission San Gabriel Arcángel and Mission San Juan Capistrano, where 40 parishioners were killed during the collapse of a church at an early morning service. Tree ring and paleoseismic evidence show that there is a strong likelihood that the earthquake originated along the Mojave segment of the San Andreas Fault near Wrightwood, but other faults have been suggested as the cause.
The 1979 Coyote Lake earthquake occurred at 10:05:24 local time on August 6 with a moment magnitude of 5.7 and a maximum Mercalli Intensity of VII. The shock occurred on the Calaveras Fault near Coyote Lake in Santa Clara County, California and resulted in a number of injuries, including some that required hospitalization. Most of the $500,000 in damage that was caused was non-structural, but several businesses were closed for repairs. Data from numerous strong motion instruments was used to determine the type, depth, and extent of slip. A non-destructive aftershock sequence that lasted throughout the remainder of the month was of interest to seismologists, especially with regard to fault creep, and following the event local governments evaluated their response to the incident.
The 1986 North Palm Springs earthquake occurred on July 8 at 02:20:44 local time with a moment magnitude of 6.0 and a maximum Mercalli Intensity of VII. The shock occurred in a complex setting along the San Andreas Fault Zone where it bisects San Gorgonio Mountain and San Jacinto Peak at the San Gorgonio Pass and was the first in a series of three earthquakes that affected southern California and the northern Owens Valley in July 1986. Numerous strong motion instruments recorded the event, one of which showed relatively high accelerations. Between 29 and 40 people were injured, and financial losses were estimated to be in the range of $4.5–6 million.
The 1980 Eureka earthquake occurred on November 8 at 02:27:34 local time along the northern coastal area of California in the United States. With a moment magnitude of 7.3 and a maximum Mercalli intensity of VII, this strike-slip earthquake was the largest to occur in California in 28 years. Although damage was considered light, several loss estimates equaled or exceeded $2 million, and six injuries resulted when two vehicles came down with the partial collapse of a highway overpass on US 101 in Fields Landing. The north coast of California experiences frequent plate boundary earthquakes near the Mendocino Triple Junction and intraplate events also occur within the Gorda Plate.
The 1892 Vacaville–Winters earthquakes occurred in northern California as a large doublet on April 19 and April 21. Measured on a seismic scale that is based on an isoseismal map or the event's felt area, the 6.4 Mla and 6.2 Mla events were assigned a maximum Mercalli intensity of IX (Violent), and affected the North Bay and Central Valley areas. The total damage was estimated to be between $225,000 and 250,000 and one person was killed. No evidence of fault movement on the surface of the ground was observed as a result of either of the strong shocks. Both occurred in the domain of the San Andreas strike-slip system of faults, but their focal mechanism is uncertain.
The 1918 San Jacinto earthquake occurred in extreme eastern San Diego County in Southern California on April 21 at 14:32:29 local time. The shock had a moment magnitude of 6.7 and a maximum Mercalli intensity of IX (Violent). Several injuries and one death occurred with total losses estimated to be $200,000.
The 1932 Eureka earthquake occurred on June 6 at 00:44:26 local time along the northern coastal area of California in the United States. With a moment magnitude of 6.4 and a maximum Mercalli intensity of VIII (Severe), this earthquake left one person dead from a falling chimney and several injured. The shock was the largest in the area since 1923 and was felt in southern Oregon and northern California.
The 1838 San Andreas earthquake is believed to be a rupture along the northern part of the San Andreas Fault in June 1838. It affected approximately 100 km of the fault, from the San Francisco Peninsula to the Santa Cruz Mountains. It was a strong earthquake, with an estimated moment magnitude of 6.8 to 7.2, making it one of the largest known earthquakes in California. The region was lightly populated at the time, although structural damage was reported in San Francisco, Oakland, and Monterey. It is unknown whether there were fatalities. Based on geological sampling, the fault created approximately 1.5 meters of slip.
The 1898 Mare Island earthquake occurred in Northern California on March 30 at 23:43 local time with a moment magnitude of 5.8–6.4 and a maximum Mercalli intensity of VIII–IX (Severe–Violent). Its area of perceptibility included much of northern and central California and western Nevada. Damage amounted to $350,000 and was most pronounced on Mare Island, a peninsula in northern San Francisco Bay. While relatively strong effects there were attributed to vulnerable buildings, moderate effects elsewhere in the San Francisco Bay Area consisted of damaged or partially collapsed structures, and there were media reports of a small tsunami and mostly mild aftershocks that followed.
The 1934 Hansel Valley earthquake occurred on March 12 at approximately 8:05 a.m. MST with a moment magnitude of 6.6 and a maximum Mercalli intensity of VIII (Severe). The shock originated in the Hansel Valley at the north end of the Great Salt Lake in Utah in the United States. Damage was mostly confined to vulnerable buildings, and two people died. The dip-slip (normal) fault that generated the shock ruptured the surface of the ground and other geologic features were documented. A large aftershock occurred three hours after the initial event and may have caused additional damage.
The 1981 Westmorland earthquake occurred at 05:09 Pacific Daylight Time on April 26. The moderate strike-slip shock took place in the Imperial Valley of Southern California, just north of the Mexico–United States border. No injuries or deaths occurred, but damage was estimated at $1–3 million. With a Mercalli intensity of VII, this was one of fifteen intensity VII or greater shocks in the Imperial Valley that were observed in the 20th century up until April 1981. The region experiences large stand-alone events and earthquake swarms due to its position in an area of complex conditions where faulting transitions from strike-slip movement to the north and divergence to the south.
The 1968 Borrego Mountain earthquake occurred on April 8, at 6:28 p.m. PST, near the unincorporated community of Ocotillo Wells in San Diego County. The moment magnitude (Mw ) 6.6 strike-slip earthquake struck with a focal depth of 11.1 km (6.9 mi). Damage was relatively moderate, and the mainshock was assigned a maximum Modified Mercalli intensity (MMI) of VII. Shaking was felt in Nevada, and Arizona. It was the largest earthquake to strike California since 1952, and its display of afterslip became the subject of scientific interest.
The 1915 Imperial Valley earthquakes were two destructive shocks centered near El Centro, California on June 22. The earthquakes measured Ms 6.25 and occurred nearly one hour apart at 19:59 and 20:57 PST. Both shocks were assigned VIII (Severe) on the Modified Mercalli intensity scale. Heavy damage occurred in the areas of Mexicali and El Centro, amounting to $900,000. At least six people were killed in the earthquakes.