1986 North Palm Springs earthquake

Last updated

1986 North Palm Springs earthquake
Relief map of California.png
Green pog.svg
Ridgecrest
Green pog.svg
Malibu
Green pog.svg
Oceanside
Green pog.svg
Bullhead City
Green pog.svg
Las Vegas
Green pog.svg
Yuma
Green pog.svg
Bishop
Bullseye1.png
UTC  time1986-07-08 09:20:44
ISC  event 490261
USGS-ANSS ComCat
Local dateJuly 8, 1986 (1986-07-08)
Local time02:20:44 PDT
Magnitude6.0 Mw [1]
Depth10 km (6.2 mi) [1]
Epicenter 34°01′N116°46′W / 34.02°N 116.76°W / 34.02; -116.76 [1]
Type Strike-slip
Areas affected Inland Empire
Southern California
United States
Total damage$4.5–6 million [2] [3]
Max. intensity VII (Very strong) [3]
Peak acceleration0.778 g [4]
Casualties29–40 injured [2] [3]

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 (Very strong). 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.

Contents

Preface

July 1986 was an unusually active month for moderate to strong earthquakes in California, with three events occurring in less than two weeks. Each had mild to moderate effects and began on July 8 with the event near Palm Springs. The second event was a Ms 5.8 shock that occurred off the coast of Oceanside on July 13. While the earthquake off the southern California coast occurred in an area thought to be capable of generating a tsunami, the earthquake near Palm Springs occurred on a portion of the southern San Andreas Fault system that has been designated a seismic gap and is a likely location for a very large future earthquake. The Chalfant Valley earthquake occurred on July 21 along the White Mountains Fault Zone near Bishop. [5]

Tectonic setting

The San Andreas Fault (SAF) spans nearly the length of California, where much it is clearly identifiable for much of its length, especially from San Francisco to near Cajon Pass. There, the fault splays into several branches. Several unusual characteristics are displayed further to the southeast in the area of the San Gorgonio Pass. There are no lateral stream offsets (that are associated with strike-slip faulting) near the pass like there are along other segments (one researcher indicated that thrust faulting was the dominant type of fault displacement at the pass). There are no great earthquakes that are known to have occurred at the pass, where the main trace of the SAF is marked by numerous sag ponds and north-facing scarps. The Banning Fault lies about two miles to the south of these features. [6]

Earthquake

Strong ground motion map for the event USGS Shakemap - 1986 Palm Springs earthquake.jpg
Strong ground motion map for the event

Early research indicated that the Banning Fault comprises three segments and that the nearly-parallel Garnet Hill Fault lies just to the south. The epicenter of the July 8 earthquake was located in this convoluted area of faults between two segments of the Banning Fault and the Mission Creek strand of the San Andreas Fault, about 16 miles (25 km) northwest of where these two faults converge to form the Coachella Valley segment of the SAF. The focal mechanism (as defined by first motions) showed pure right-lateral strike-slip on a fault trending west-northwest that dipped to the north at 45°. As many of the aftershocks and previous events in the area showed oblique-reverse motion, researchers did not exclude the possibility that the rupture started as horizontal motion, then transitioned into movement that included some vertical motion. [7]

Damage

In North Palm Springs, four homes and 16 businesses were destroyed, and an additional 100 mobile homes and 100 businesses were damaged. In Whitewater Canyon, chimneys fell and three homes were destroyed; ceramic columns were broken and a transformer was displaced at the Devers electrical substation. The Windy Point Bridge was displaced on I-10 northwest of Palm Springs, causing a separation of the deck and abutment. [3]

Other temporary roadway closures included State Route 111, which was closed until the following evening, and State Route 74 and State Route 243 that were reopened later in the day. State Route 62, which crosses the Banning and Mission Creek faults, was not immediately reopened due to buckled pavement. The California Aqueduct was damaged at several locations and water had to be diverted into a lake bed, and up to 80,000 people lost power for a portion of the day. Two fires in Riverside County caused serious damage, including a glass company that sustained $45,000 in damage, and several other brush fires. [8]

Strong motion

The shock was captured by strong motion stations that were operated by the United States Geological Survey, California Division of Mines and Geology, University of Southern California and Kinemetrics Inc., a private company. Altogether, the networks comprised about 75 stations, mainly including ground response stations, but also included 17 buildings, nine dams, a power plant, and a freeway interchange. The stations were triggered at distances of up to 110 miles (180 km), with a strong motion duration of greater than three seconds at five of the closest stations. The strongest acceleration (0.778 g ) occurred at the North Palm Springs Post Office on the vertical axis. [4]

Intensity

The maximum intensity for the event was VII (Very strong). At Desert Hot Springs, effects aligned with this rating were broken underground pipes (including a 5-inch water main) and filing cabinets that were knocked over at city hall. At the Devers substation near North Palm Springs, 75 percent of the ceramic lightning arrestors and circuit breakers were damaged, and a 650,000 lb. transformer was dislocated 10 inches. A building collapsed at a drug and alcohol recovery facility and the White Water overpass was damaged due to lateral movement at its south abutment in Palm Springs. Broken glass and cracks in walls and concrete columns (some severe) were also widespread there. [9]

Intensity VI (Strong) effects were widespread, from La Jolla and Pacific Beach area near San Diego to Seal Beach in the Los Angeles area that were deemed to qualify. The effects at this level included cracked walls and windows and small landslides, and were more prevalent in the Banning Pass and Palm Springs Area areas. The area of perceptibility for the mainshock was large (130,500 km2), from Malibu and Ridgecrest in California, to Bullhead City and Yuma in Arizona, and Las Vegas in southern Nevada. [9]

See also

Related Research Articles

<span class="mw-page-title-main">1971 San Fernando earthquake</span> Earthquake in California

The 1971 San Fernando 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 of 6.5 on the Ms scale and 6.6 on the Mw scale, and a maximum Mercalli intensity of XI (Extreme). The event was one in a series that affected Los Angeles county in the late 20th century. Damage was locally severe in the northern San Fernando Valley and surface faulting was extensive to the south of the epicenter in the mountains, as well as urban settings along city streets and neighborhoods. Uplift and other effects affected private homes and businesses.

<span class="mw-page-title-main">1987 Whittier Narrows earthquake</span> Earthquake in southern California

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 1952 Kern County earthquake occurred on July 21 in the southern San Joaquin Valley and measured 7.3 on the moment magnitude scale. The main shock occurred at 4:52 am Pacific Daylight Time, killed 12 people, injured hundreds more and caused an estimated $60 million in property damage. A small sector of damage near Bealville corresponded to a maximum Mercalli intensity of XI (Extreme), though this intensity rating was not representative of the majority of damage. The earthquake occurred on the White Wolf Fault near the community of Wheeler Ridge and was the strongest to occur in California since the 1906 San Francisco earthquake.

<span class="mw-page-title-main">1983 Coalinga earthquake</span> Earthquake affecting Central California

The 1983 Coalinga earthquake struck at 4:42 p.m. Monday, May 2 of that year, in Coalinga, California.

<span class="mw-page-title-main">San Jacinto Fault Zone</span> Southern Californian 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 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 1986 Chalfant Valley earthquake struck southern Mono County near Bishop and Chalfant, California at 07:42:28 Pacific Daylight Time on July 21. With a moment magnitude of 6.2 and a maximum Mercalli intensity of VI (Strong), the shock injured two people and caused property damage estimated at $2.7 million in the affected areas. There was a significant foreshock and aftershock sequence that included a few moderate events, and was the last in a series of three earthquakes that affected southern California and the northern Owens Valley in July 1986.

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 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 1991 Sierra Madre earthquake occurred on June 28 at 07:43:55 local time with a moment magnitude of 5.6 and a maximum Mercalli intensity of VII. The thrust earthquake resulted in two deaths, around 100 injuries, and damage estimated at $33.5–40 million. The event occurred beneath the San Gabriel Mountains on the Clamshell–Sawpit Fault, which is a part of the Sierra Madre–Cucamonga Fault System. Instruments captured the event at a number of strong motion stations in Southern California.

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 1957 San Francisco earthquake occurred on March 22 at 11:44:22 local time with a moment magnitude of 5.7 and a maximum Mercalli Intensity of VII. It was located just off the San Francisco Peninsula near the San Andreas Fault and was felt in a limited portion of Northern and Central California. There was a non-destructive foreshock and aftershock sequence that lasted for several months. With financial losses of around US$1 million, damage was considered minimal, with one death and forty injuries.

The 1990 Upland earthquake occurred at 15:43:37 local time on February 28 with a moment magnitude of 5.7 and a maximum Mercalli Intensity of VII. This left-lateral strike-slip earthquake occurred west of the San Andreas Fault System and injured thirty people, with total losses of $12.7 million. Many strong motion instruments captured the event, with an unexpectedly high value seen on water tank near the epicentral area.

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 2019 Ridgecrest earthquakes of July 4 and 5 occurred north and northeast of the town of Ridgecrest, California located in Kern County and west of Searles Valley. They included three initial main shocks of Mw magnitudes 6.4, 5.4, and 7.1, and many perceptible aftershocks, mainly within the area of the Naval Air Weapons Station China Lake. Eleven months later, a Mw  5.5 aftershock took place to the east of Ridgecrest. The first main shock occurred on Thursday, July 4 at 10:33 a.m. PDT, approximately 18 km (11.2 mi) ENE of Ridgecrest, and 13 km (8.1 mi) WSW of Trona, on a previously unnoticed NE-SW trending fault where it intersects the NW-SE trending Little Lake Fault Zone. This quake was preceded by several smaller earthquakes, and was followed by more than 1,400 detected aftershocks. The M 5.4 and M 7.1 quakes struck on Friday, July 5 at 4:08 a.m. and 8:19 p.m. PDT approximately 10 km (6 miles) to the northwest. The latter, now considered the mainshock, was the most powerful earthquake to occur in the state in 20 years. Subsequent aftershocks extended approximately 50 km (~30 miles) along the Little Lake Fault Zone.

The 1987 Superstition Hills and Elmore Ranch earthquakes were a pair of earthquakes measuring Mw  6.0 and 6.5 that rattled the Imperial Valley of California. The earthquakes caused damage in Southern California and Mexico, but was limited due to their location in a sparsely populated area. It was felt as far as Las Vegas and Phoenix. More than 90 were injured, and two people were killed in Mexico.

The 1968 Borrego Mountain earthquake occurred on April 8, at 18:28 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 1992 Joshua Tree earthquake occurred at 9:50:25 p.m. PDT on April 22 in Southern California. The magnitude 6.2 earthquake struck under the Little San Bernardino Mountains, near the town of Joshua Tree, California. Though no deaths were reported, the earthquake caused 32 injuries. A maximum Mercalli intensity of VII was observed in Joshua Tree and caused light to moderate damage. The event preceded the Landers and Big Bear 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.

References

  1. 1 2 3 ISC (January 19, 2015), ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009), Version 2.0, International Seismological Centre, archived from the original on November 25, 2016, retrieved June 13, 2015
  2. 1 2 USGS (September 4, 2009), PAGER-CAT Earthquake Catalog, Version 2008_06.1, United States Geological Survey, archived from the original on October 4, 2016, retrieved December 20, 2017
  3. 1 2 3 4 Stover, C. W.; Coffman, J. L. (1993), Seismicity of the United States, 1568–1989 (Revised) – U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, pp. 97, 177, archived from the original on April 13, 2019, retrieved October 29, 2016
  4. 1 2 Porcella, R. L.; Etheredge, E. C.; Maley, R. P.; Switzer, J. C. (1987), "Strong-motion data from the July 8, 1986 North Palm Springs earthquake and aftershocks", Strong motion data from the July 8, 1986 North Palm Springs earthquake and its aftershocks, Geological Survey Open File Report 87-155, United States Geological Survey, pp. 1–5, 28, doi:10.3133/ofr87155, archived from the original on June 16, 2015, retrieved August 28, 2017
  5. ↑ Pacheco, J.; Nabelek, J. (December 1, 1988), "Source mechanisms of three moderate California earthquakes of July 1986", Bulletin of the Seismological Society of America, 78 (6): 1907–1909
  6. ↑ Allen, C. R. (1954), The San Andreas Fault Zone in San Gorgonio Pass, California (phd), Dissertation (Ph.D.), California Institute of Technology, pp. 1, 4, 7, 92, 93, 96, doi:10.7907/54GN-M254, archived from the original on August 15, 2020, retrieved August 27, 2019
  7. ↑ Jones, L. M.; Hutton, L. K.; Given, D. D.; Allen, C. R. (December 1, 1986), "The North Palm Springs, California, earthquake sequence of July 1986", Bulletin of the Seismological Society of America, 76 (6): 1830–1833, Bibcode:1986BuSSA..76.1830J, doi:10.1785/BSSA0760061830, archived from the original on September 23, 2015, retrieved June 13, 2015
  8. ↑ Arnold, Roxane; Malnic, Eric (July 9, 1986). "Strong Quake in Desert Rolls Across Southland : 6.0 Temblor Awakens Residents in Wide Area; Damage Limited by Remote Site of Epicenter". Los Angeles Times . Archived from the original on June 16, 2015. Retrieved June 13, 2015.
  9. 1 2 Stover, C. W.; Brewer, L. R. (1994), United States earthquakes, 1986 (PDF), U.S. Geological Survey Bulletin 2089, United States Government Printing Office, pp. 32–41, archived (PDF) from the original on May 1, 2017, retrieved October 6, 2017
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.