![California Department of Conservation - Earthquake Shaking Potential for California](https://upload.wikimedia.org/wikipedia/commons/5/53/California_Department_of_Conservation_-_Earthquake_Shaking_Potential_for_California.jpg)
The earliest known California earthquake was documented in 1769 by the Spanish explorers and Catholic missionaries of the
Portolá expedition
thumbnail, 250px, Point of San Francisco Bay Discovery
The Portolá expedition ( es, Expedición de Portolá) was a Spanish voyage of exploration in 1769–1770 that was the first recorded European land entry and exploration of the interior of t ...
as they traveled northward from
San Diego
San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the List of United States cities by population, eigh ...
along the
Santa Ana River
The Santa Ana River is the largest river entirely within Southern California in the United States. It rises in the San Bernardino Mountains and flows for most of its length through San Bernardino and Riverside Counties, before cutting through ...
near the present site of
Los Angeles
Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...
. Ship captains and other explorers also documented earthquakes. As
Spanish missions
The Spanish missions in the Americas were Catholic missions established by the Spanish Empire during the 16th to 19th centuries in the period of the Spanish colonization of the Americas. These missions were scattered throughout the entirety of ...
were constructed beginning in the late 18th century, earthquakes records were kept. After the missions were
secularized
In sociology, secularization (or secularisation) is the transformation of a society from close identification with religious values and institutions toward non-religious values and secular institutions. The ''secularization thesis'' expresses the ...
in 1834, records were sparse until the
California Gold Rush
The California Gold Rush (1848–1855) was a gold rush that began on January 24, 1848, when gold was found by James W. Marshall at Sutter's Mill in Coloma, California. The news of gold brought approximately 300,000 people to California fro ...
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
The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...
and the
East Coast
East Coast may refer to:
Entertainment
* East Coast hip hop, a subgenre of hip hop
* East Coast (ASAP Ferg song), "East Coast" (ASAP Ferg song), 2017
* East Coast (Saves the Day song), "East Coast" (Saves the Day song), 2004
* East Coast FM, a ra ...
(
1755 Cape Ann,
1811–12 New Madrid,
1886 Charleston) were well known, it became apparent to
settler
A settler is a person who has human migration, migrated to an area and established a permanent residence there, often to colonize the area.
A settler who migrates to an area previously uninhabited or sparsely inhabited may be described as a ...
s 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
A financial centre (British English, BE), financial center (American English, AE), or financial hub, is a location with a concentration of Global financial system#Participants, participants in banking, asset management, insurance or financial ...
of the
San Francisco Bay Area
The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Go ...
, with damage from
Santa Rosa
Santa Rosa is the Italian, Portuguese and Spanish name for Saint Rose.
Santa Rosa may also refer to:
Places Argentina
*Santa Rosa, Mendoza, a city
* Santa Rosa, Tinogasta, Catamarca
* Santa Rosa, Valle Viejo, Catamarca
* Santa Rosa, La Pampa
* S ...
in the north to
Santa Cruz in the south. By this time, scientists were well aware of the threat, but
seismology
Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...
was still in its infancy. Following destructive earthquakes in the late 19th and early 20th centuries,
real estate developers
Real estate development, or property development, is a business process, encompassing activities that range from the renovation and re-lease of existing buildings to the purchase of raw land and the sale of developed land or parcels to others. R ...
,
press
Press may refer to:
Media
* Print media or news media, commonly called "the press"
* Printing press, commonly called "the press"
* Press (newspaper), a list of newspapers
* Press TV, an Iranian television network
People
* Press (surname), a fam ...
, and
boosters minimized and downplayed the risk of earthquakes out of fear that the ongoing
economic boom
An economic expansion is an increase in the level of economic activity, and of the goods and services available. It is a period of economic growth as measured by a rise in real GDP. The explanation of fluctuations in aggregate economic activity ...
would be negatively affected.
![California Department of Conservation – Earthquake map (1769–2000)](https://upload.wikimedia.org/wikipedia/commons/6/64/California_Department_of_Conservation_%E2%80%93_Earthquake_map_%281769%E2%80%932000%29.gif)
According to seismologist
Charles Richter
Charles Francis Richter (; April 26, 1900 – September 30, 1985) was an American seismologist and physicist.
Richter is most famous as the creator of the Richter magnitude scale, which, until the development of the moment magnitude scale in 19 ...
, the
1906 San Francisco earthquake
At 05:12 Pacific Standard Time on Wednesday, April 18, 1906, the coast of Northern California was struck by a major earthquake with an estimated moment magnitude of 7.9 and a maximum Mercalli intensity of XI (''Extreme''). High-intensity sha ...
moved the
United States Government
The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a fede ...
into acknowledging the problem. Prior to that, no agency was specifically focused on researching earthquake activity. The
United States Weather Bureau
The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the p ...
did record when they happened and several
United States Geological Survey
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
scientists had briefly disengaged from their regular duties of mapping
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
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
The United States Coast and Geodetic Survey (abbreviated USC&GS), known from 1807 to 1836 as the Survey of the Coast and from 1836 until 1878 as the United States Coast Survey, was the first scientific agency of the United States Government. It ...
was made responsible. The outlook improved when Professor
Andrew Lawson
Andrew Cowper Lawson (July 25, 1861 – June 16, 1952) was a Scots-Canadian geologist who became professor of geology at the University of California, Berkeley. He was the editor and co-author of the 1908 report on the 1906 San Francisco earthq ...
brought the state's
first monitoring program online at the
University of California, Berkeley
The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
in 1910 with seismologist
Harry Wood, who was later instrumental in getting the
Caltech Seismological Laboratory in
Pasadena
Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district.
Its ...
operational in the 1920s.
Early developments at the Caltech
The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
lab included an earthquake observation network using their own custom-built short-period seismometer
A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The outpu ...
s, the Richter magnitude scale
The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 ...
, and the Modified Mercalli intensity scale
The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...
(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
The 1971 San Fernando earthquake (also known as the 1971 Sylmar earthquake) occurred in the early morning of February 9 in the foothills of the San Gabriel Mountains in southern California. The unanticipated thrust earthquake had a magnitude o ...
affected the San Fernando Valley
The San Fernando Valley, known locally as the Valley, is an urbanized valley in Los Angeles County, California. Located to the north of the Los Angeles Basin, it contains a large portion of the City of Los Angeles, as well as unincorporated ar ...
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 code
A building code (also building control or building regulations) is a set of rules that specify the standards for constructed objects such as buildings and non-building structures. Buildings must conform to the code to obtain planning permission ...
s 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 fault
An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...
s.[
]
Tectonic setting
During the last 66 million years, nearly the entire west coast of North America was dominated by a subduction
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
zone, with the Farallon Plate
The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west c ...
subducting beneath the North American Plate
The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...
. Presently, the Juan de Fuca Plate (with its Explorer
Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians.
Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...
and Gorda satellite plates) and the Rivera
Rivera () is the capital of Rivera Department of Uruguay. The border with Brazil joins it with the Brazilian city of Santana do Livramento, which is only a street away from it, at the north end of Route 5. Together, they form an urban area of aro ...
and Cocos Plate
The Cocos Plate is a young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it. The Cocos Plate was created approximately 23 million years ago when the Farallon Plate ...
s are the only remnants of the once much larger Farallon Plate. The plate margin that remains in California is that of the strike-slip
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
San Andreas Fault
The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonics, tectonic boundary between the Pacific Plate and the North American Plate, and its motion is Fault (geology)#Strike-slip fau ...
(SAF), the diffuse
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
–North American plate boundary that extends east into the Basin and Range Province
The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...
of eastern California
Eastern California is a region defined as either the strip to the east of the crest of the Sierra Nevada or as the easternmost counties of California.
Demographics
According to the 2010 census, the population of the eastern border counties of Ca ...
and western Nevada
Western Nevada (WNV) is a region and the northwestern portion of the U.S. state of Nevada that includes Reno, Carson City, Carson Valley and Virginia City. Lyon County and Churchill County are sometimes also referred to as part of Western Nevada. ...
(a seismically active area called Walker Lane
The Walker Lane is a geologic trough roughly aligned with the California/Nevada border southward to where Death Valley intersects the Garlock Fault, a major left lateral, or sinistral, strike-slip fault. The north-northwest end of the Walker L ...
) 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
The Mendocino Triple Junction (MTJ) is the point where the Gorda plate, the North American plate, and the Pacific plate meet, in the Pacific Ocean near Cape Mendocino in northern California. This triple junction is the location of a change in the ...
, one of the most seismically active regions in the state, where earthquakes are occasionally the result of intraplate deformation
Intraplate deformation is the folding, breaking, or flow of the Earth's crust within plates instead of at their margins. This process usually occurs in areas with especially weak crust and upper mantle, such as the Tibetan Plateau (Figure 1). Int ...
within the Gorda Plate. It terminates in the south at the Salton Sea
The Salton Sea is a shallow, landlocked, highly saline body of water in Riverside and Imperial counties at the southern end of the U.S. state of California. It lies on the San Andreas Fault within the Salton Trough that stretches to the Gulf o ...
where displacement transitions to a series of spreading centers and transform fault
A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...
s, beginning with the Brawley Seismic Zone
The Brawley Seismic Zone (BSZ), also known as the Brawley fault zone, is a predominantly extensional tectonic zone that connects the southern terminus of the San Andreas Fault with the Imperial Fault in Southern California. The BSZ is named for ...
in the Imperial Valley
, photo = Salton Sea from Space.jpg
, photo_caption = The Imperial Valley below the Salton Sea. The US-Mexican border runs diagonally across the lower left of the image.
, map_image = Newriverwatershed-1-.jpg
, map_caption = Map of Imperial ...
.
In the San Francisco Bay Area
The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Go ...
, 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
The Hayward Fault Zone is a right-lateral strike-slip geologic fault zone capable of generating destructive earthquakes. This fault is about long, situated mainly along the western base of the hills on the east side of San Francisco Bay. It runs ...
, which has gone beyond its average return period A return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquakes, floods, landslides, or river discharge flows to occur.
It is a statistical measurement typ ...
of 130 years ( as of ). While the SAF is quiet north of San Francisco
San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...
, the central SAF segment near San Juan Bautista is where aseismic creep
In geology, aseismic creep or fault creep is measurable surface displacement along a fault in the absence of notable earthquakes. Aseismic creep may also occur as "after-slip" days to years after an earthquake. Notable examples of aseismic slip in ...
was first studied, and to the south is where the recurring Parkfield earthquake
Parkfield earthquake is a name given to various large earthquakes that occurred in the vicinity of the town of Parkfield, California, United States. The San Andreas fault runs through this town, and six successive magnitude 6 earthquakes occurred ...
s 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
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 i ...
, which may be taking over as the primary boundary south of Cajon Pass
Cajon Pass (; Spanish: ''Puerto del Cajón'' or ''Paso del Cajón'') is a mountain pass between the San Bernardino Mountains to the east and the San Gabriel Mountains to the west in Southern California. Created by the movements of the San Andreas ...
. A paleoseismic investigation using Lidar
Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be ...
revealed that more than of slip has accumulated since the 1857 event on the southern SAF, which borders the Mojave Desert
The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in ...
to the north and east of the Greater Los Angeles Area. Near the Transverse Ranges
The Transverse Ranges are a group of mountain ranges of southern California, in the Pacific Coast Ranges physiographic region in North America. The Transverse Ranges begin at the southern end of the California Coast Ranges and lie within Santa B ...
, reverse
Reverse or reversing may refer to:
Arts and media
* ''Reverse'' (Eldritch album), 2001
* ''Reverse'' (2009 film), a Polish comedy-drama film
* ''Reverse'' (2019 film), an Iranian crime-drama film
* ''Reverse'' (Morandi album), 2005
* ''Reverse'' ...
and thrust fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
Thrust geometry and nomenclature
Reverse faults
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less.
If ...
s have produced damaging earthquakes in Santa Barbara and the San Fernando Valley
The San Fernando Valley, known locally as the Valley, is an urbanized valley in Los Angeles County, California. Located to the north of the Los Angeles Basin, it contains a large portion of the City of Los Angeles, as well as unincorporated ar ...
.[
]
Notable earthquakes
See also
* Alquist Priolo Special Studies Zone Act
*California earthquake forecast The 2015 Uniform California Earthquake Rupture Forecast, Version 3, or UCERF3, is the latest official earthquake rupture forecast (ERF) for the state of California, superseding UCERF2. It provides authoritative estimates of the likelihood and seve ...
*Field Act
The Field Act was one of the first pieces of legislation that mandated earthquake-resistant construction (specifically for schools in California) in the United States. The Field Act had its genesis in the 6.4 magnitude 1933 Long Beach earthquake w ...
*Geography of California
California is a U.S. state on the western coast of North America. Covering an area of , California is among the most geographically diverse states. The Sierra Nevada, the fertile farmlands of the Central Valley, and the arid Mojave Desert of t ...
*Geology and geological history of California
The geology of California is highly complex, with numerous mountain ranges, substantial faulting and tectonic activity, rich natural resources and a history of both ancient and comparatively recent intense geological activity. The area formed as a ...
*Southern California Earthquake Center
The Southern California Earthquake Center (SCEC) is a collaboration of more than 1,000 scientists across 100 research institutions with a mission to: conduct research on earthquakes in Southern California and elsewhere by gathering data, conductin ...
*Timeline of the Portolá expedition
This timeline of the Portolá expedition tracks the progress during 1769 and 1770 of the first European exploration-by-land of north-western coastal areas in what became ''Las Californias'', a province of Spanish colonial New Spain. Later, the ...
References
Sources
*
Further reading
*
*
External links
Information by Region-California
– USGS
Southern California Earthquake Data Center
Putting Down Roots in Earthquake Country
– Earthquake Country Alliance
Broadband Seismic Data Collection Center
– University of California, San Diego
The University of California, San Diego (UC San Diego or colloquially, UCSD) is a public university, public Land-grant university, land-grant research university in San Diego, California. Established in 1960 near the pre-existing Scripps Insti ...
What Will Happen After The 'Big One' Hits SoCal?
– KCET
KCET (channel 28) is a secondary PBS member television station in Los Angeles, California, United States. It is owned by the Public Media Group of Southern California alongside the market's primary PBS member, Huntington Beach–licensed KOCE-TV ...
Little-known quake, tsunami hazards lurk offshore of Southern California
– American Geophysical Union
The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's act ...
California’s other drought: A major earthquake is overdue
– ''The Conversation
''The Conversation'' is a 1974 American mystery thriller film written, produced, and directed by Francis Ford Coppola and starring Gene Hackman, John Cazale, Allen Garfield, Cindy Williams, Frederic Forrest, Harrison Ford, Teri Garr, and Rober ...
''
New California bill aims to create a public inventory of collapse-risk buildings
– Temblor, Inc.
{{Authority control
Earthquakes
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
Earthquakes
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...
*
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
Tsunamis in the United States