The 1992 Joshua Tree earthquake occurred at 9:50:25 p.m. PDT (04:50:25 UTC) on April 22 in

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...

. The magnitude 6.2

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

struck under the Little San Bernardino Mountains, near the town of

Joshua Tree, California Joshua Tree is a census-designated place (CDP) in San Bernardino County, California, United States. The population was 6,489 at the 2020 census. At approximately above sea level, Joshua Tree and its surrounding communities are located in the Hig ...

. Though no deaths were reported, the earthquake caused 32 injuries. A maximum Mercalli intensity of VII (''Very Strong'') was observed in Joshua Tree and caused light to moderate damage. The event preceded the Landers and

Big Bear Big Bear, also known as (; – 17 January 1888), was a powerful and popular Cree chief who played many pivotal roles in Canadian history. He was appointed to chief of his band at the age of 40 upon the death of his father, Black Powder, u ...

earthquakes by two months but is now recognized as the beginning of a series of major earthquakes that culminated in two events on June 28, 1992.

Earthquake

The Joshua Tree mainshock struck at 9:50:25 p.m. It was caused by north-northwest-trending, right-lateral strike-slip faulting on the Eureka Peak fault which is at least long and possibly handles a significant portion of the slip transferred from the

San Andreas Fault The San Andreas Fault is a continental Fault (geology)#Strike-slip faults, right-lateral strike-slip transform fault that extends roughly through the U.S. state of California. It forms part of the tectonics, tectonic boundary between the Paci ...

zone. Its epicenter was centered about east of

Downtown Los Angeles Downtown Los Angeles (DTLA) is the central business district of the city of Los Angeles. It is part of the Central Los Angeles region and covers a area. As of 2020, it contains over 500,000 jobs and has a population of roughly 85,000 residents ...

and about deep. The shaking was reportedly felt as far away as

San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...

Santa Barbara, California Santa Barbara (, meaning ) is a coastal city in Santa Barbara County, California, of which it is also the county seat. Situated on a south-facing section of coastline, the longest such section on the West Coast of the United States excepting A ...

Las Vegas Las Vegas, colloquially referred to as Vegas, is the most populous city in the U.S. state of Nevada and the county seat of Clark County. The Las Vegas Valley metropolitan area is the largest within the greater Mojave Desert, and second-l ...

Yuma, Arizona Yuma is a city in and the county seat of Yuma County, Arizona, United States. The city's population was 95,548 at the 2020 census, up from the 2010 census population of 93,064. Yuma is the principal city of the Yuma, Arizona, Metropolitan ...

, and

Phoenix, Arizona Phoenix ( ) is the List of capitals in the United States, capital and List of cities and towns in Arizona#List of cities and towns, most populous city of the U.S. state of Arizona. With over 1.6 million residents at the 2020 census, it is the ...

. Approximately two months later, the strongest earthquake in 40 years since the

1952 Kern County earthquake Year 195 ( CXCV) was a common year starting on Wednesday of the Julian calendar. At the time, it was known in Rome as the Year of the Consulship of Scrapula and Clemens (or, less frequently, year 948 ''Ab urbe condita''). The denomination 195 f ...

hit Southern California and caused 92 million dollars in damage. The magnitude 6.2 earthquake that occurred in Joshua Tree, California, on April 22, 1992, was a previously unmapped north-facing earthquake located about 20 km south of the Mount Pinto fault and about 10 km northeast of the mission and a maximum fault slip of was estimated. It was attributed to the right fault along the Late Quaternary Fault. The Creek is a tributary of the San Andreas Fault system. The proximity of the epicenter to the Coachella Valley segment, a particularly dangerous part of the San Andreas fault, immediately raised concerns that it could be a precursor to a larger earthquake. This prompted the California Department of Emergency Services to issue a warning of possible future activity in the local counties shortly after the earthquake.

Impact

Although this earthquake did not have surface faulting that was observed, the rupture propagated northward 12 miles (19 km) to the town of Joshua Tree, where it caused damage. It caused minor damage to several bridges and minor architectural damage to public school buildings. A supermarket was damaged. 32 people were injured by the quake. Of the 170 public school facilities in the earthquake's geographic area, 10 had minor structural damage, ranging from cracks in plaster to hairline cracks in masonry walls. 48 bridges were inspected after the earthquake, and 13 showed signs of movement, nine of which were slightly damaged. None of the bridges suffered damage severe enough to affect its traffic. In some areas, it was felt for at least 60 seconds. It temporarily shut down at least one television station, but Downtown Los Angeles electrical service was not affected. The quake rattled Southern California, temporarily disrupting phone service from east of Riverside to the Arizona border. At the Hyatt Regency Suites in

Palm Springs Palm Springs (Cahuilla language, Cahuilla: ''Séc-he'') is a desert resort city in Riverside County, California, United States, within the Colorado Desert's Coachella Valley. The city covers approximately , making it the largest city in Rivers ...

, chief security officer Jerry Iovine reported that guests on the top floor had been temporarily evacuated while construction experts examined the structure of the six-story hotel. The Governor's Office of Emergency Services issued advisories to six counties telling officials in Riverside, San Bernardino, Imperial, Los Angeles, Orange, and San Diego counties that they should be on alert for another, larger quake.

Aftershocks

The earthquake had more than 6,000

aftershocks In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousands ...

, the largest with a magnitude of 4.8. A foreshock of magnitude 4.6 occurred about two hours before the main quake. The aftershocks spread along a northward trend from about north of the San Andreas Fault northwest of

Indio, California Indio (Spanish language, Spanish for "Indian") is a city in Riverside County, California, United States, in the Coachella Valley of Southern California's Colorado Desert region. Indio is approximately east of Los Angeles, east of Palm Springs, ...

to the east-striking Mount Pinto Fault and it also preceded the Landers event near the southern end of the future Landers aftershock zones. The aftershock sequence of the Joshua Tree quake also showed a clear relative calm during the period before the Landers rupture.

References

{{Earthquakes in the United States Earthquakes in California 1992 earthquakes 1992 in California Strike-slip earthquakes 1992 natural disasters in the United States April 1992 in the United States

Earthquake

Impact

Aftershocks

See also

References