1899 San Jacinto earthquake
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The 1899 San Jacinto earthquake occurred on Christmas morning (December 25) at 04:25 local time in
Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most po ...
. The estimated
moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...
6.7 earthquake had an epicenter located 10 miles southeast of San Jacinto. The earthquake had a maximum
Mercalli intensity 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 ...
of IX (''Violent''). Severe damage occurred, amounting to US$50,000 (1899 rate), as well as six fatalities.


Tectonic setting

The mainshock occurred on a segment of the
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 is ...
. This highly segmented, 210-km-long strike-slip fault that forms part of the boundary between the North American and Pacific plates. The fault is part of a complex plate boundary system known as the San Andreas Fault System. It runs parallel to the
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 ...
, west of 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 ...
, and is separated from the San Andreas Fault by the
San Jacinto Mountains The San Jacinto Mountains (''Avii Hanupach''Munro, P., et al. ''A Mojave Dictionary''. Los Angeles: UCLA. 1992. in Mojave) are a mountain range in Riverside County, located east of Los Angeles in southern California in the United States. The mou ...
to its east. It cuts under cities including
Hemet Hemet is a city in the San Jacinto Valley in Riverside County, California. It covers a total area of , about half of the valley, which it shares with the neighboring city of San Jacinto. The population was 89,833 at the 2020 census. The foundin ...
, Colton, and
San Bernardino San Bernardino (; Spanish language, Spanish for Bernardino of Siena, "Saint Bernardino") is a city and county seat of San Bernardino County, California, United States. Located in the Inland Empire region of Southern California, the city had a ...
along the way, before joining the San Andreas Fault at
Devore Devore may refer to: * Devoré, a fabric technique *Devore, San Bernardino, California *Devore, Indiana People with the surname *Chuck DeVore (born 1962), American politician * Daniel Bradford Devore, (1860–1956), American brigadier general *Doro ...
. Because the fault is so segmented, some branches have their own names, although they are considered part of the system of faults. The San Jacinto Fault is thought to be the most active fault in California. It is the source of at least 11 earthquakes measuring 6.0 or greater since the late 19th century. The most recent earthquakes were the doublet event of 1987. The 1987 pair of temblors inflicted heavy damages to
Westmorland Westmorland (, formerly also spelt ''Westmoreland'';R. Wilkinson The British Isles, Sheet The British IslesVision of Britain/ref> is a historic county in North West England spanning the southern Lake District and the northern Dales. It had an ...
, and indirectly killed two people outside
Mexicali Mexicali (; ) is the capital city of the Mexican state of Baja California. The city, seat of the Mexicali Municipality, has a population of 689,775, according to the 2010 census, while the Calexico–Mexicali metropolitan area is home to 1,000, ...
. Another strong earthquake struck nearby in 1968.


Earthquake

The 1899 earthquake occurred on a segment of the San Jacinto Fault that also ruptured in a similar-sized quake in 1918. A study on earthquakes on the San Jacinbto Fault found that the earthquakes had lowered the coulomb stress on the southern segment of the San Andreas Fault, delaying the occurrence of a large rupture. The last San Andreas Fault rupture in the region was in 1680. The
San Jacinto Valley The San Jacinto Valley is a valley located in Riverside County, California, Riverside County, in Southern California, in the Inland Empire. The valley is located at the base of the San Jacinto Mountains in the east and Santa Rosa Hills (Riversid ...
segment is believed to be the source of the 1899 earthquake. The rupture is located within the valley area, possibly on the Casa Loma strand.


Damage

Lasting 30 seconds, damage was severe. Many, but not all brick buildings in the Hemet and San Jacinto were demolished. Every brick building on Main Street was extensively damaged, littering the road with bricks. Two-storey buildings lost their second floors and power lines were down. The San Jacinto County Hospital was completely unrecognizable after many of its brick walls were torn off. Despite the extent of damage, the occupants were unharmed. In Hemet, the quake knocked off all but two chimneys. The Hemet Hotel suffered extensive damage and a veranda on the west wall was completely torn. Many bricks fell from the building and it was eventually unsafe for use. Every high school in the city was damaged, delaying school reopenings after the Christmas holidays. Brick structures suffered partial collapses while wood-constructed buildings shifted off their foundations. A 150-foot-long
fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure A ...
formed beneath a house, twisting and wrenching its wooden frame. This fissure is thought to be a
surface rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where the ...
of the fault. In
Riverside Riverside may refer to: Places Australia * Riverside, Tasmania, a suburb of Launceston, Tasmania Canada * Riverside (electoral district), in the Yukon * Riverside, Calgary, a neighbourhood in Alberta * Riverside, Manitoba, a former rural m ...
, chimneys toppled and brick buildings suffered cracks. In the Soboba Indian Reservation, Riverside County, six elders of the
Soboba Band of Luiseño Indians The Soboba Band of Luiseño Indians is a federally recognized tribe of Luiseño people, headquartered in Riverside County, California. On June 18, 1883, the Soboba Reservation was established by the United States government in San Jacinto. There ...
were killed. A further eight were seriously injured when an adobe wall fell. At
Murrieta Murrieta is a city in southwestern Riverside County, California, United States. The population of Murrieta was 110,949 as of the 2020 United States Census, 2020 census. Murrieta experienced a 133.7% population increase between 2000 and 2010, ma ...
, the quake destroyed an adobe home. Two-thirds of the city's homes were slightly damaged. Damage was also reported in the San Bernardino-Banning area. There was some minimal damage as far away as Los Angeles and San Diego. A major
landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
occurred in the San Jacinto Mountains and a
rockslide A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses ''en masse'' and not in individual blocks. Note that a rockslide is similar to an avalanc ...
at Escondido. Increased flow of water at a spring was observed at Murrieta Hot Springs and Sage, and
hot spring A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...
s formed at
Jacumba Jacumba Hot Springs ( ) is an unincorporated community in the Mountain Empire area of southeastern San Diego County, California, United States. For statistical purposes, the United States Census Bureau defined Jacumba Hot Springs as a census-des ...
. The San Bernardino Transcript reported that large dust clouds formed on the San Jacinto Mountains. The forest patrol thought the clouds were from a fire but when they arrived, a large fissure six feet wide and was formed.


See also

*
List of earthquakes in California 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 ...
*
List of earthquakes in the United States The following is a list of notable earthquakes and tsunamis which had their epicenter in areas that are now part of the United States with the latter affecting areas of the United States. Those in ''italics'' were not part of the United States whe ...


References

{{Earthquakes in the United States 1899 earthquakes Earthquakes in California 1899 natural disasters in the United States 1899 in California San Jacinto, California History of Riverside County, California