San Jacinto Fault Zone

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Map showing the San Jacinto Fault Zone outlined in red USGS - San Jacinto Fault Zone.gif
Map showing the San Jacinto Fault Zone outlined in red

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.

Contents

The SJFZ itself consists of many individual fault segments, some of which have only been individualized as recently as the 1980s, but activity along the line of faults has been documented since the 1890s. One segment of the SJFZ, the Anza seismic gap, has not experienced any major activity since instrumental records have been kept. Each segment was evaluated for its seismic risk and was assigned a probability for the occurrence of a large rupture for the thirty-year period starting in 1995.

While several of the large earthquakes along the SJFZ have not resulted in significant property damage or loss of life (due to their remote location) the cities of Hemet and San Jacinto were both heavily damaged in two significant events in 1899 and 1918. The recurrence interval for a series of large earthquakes starting in 1899 (including the 5.9 1937 Terwilliger Valley earthquake) was 18, 5, 14, 5, 12, 14, and 19 years, yet there has not been a strong earthquake for 36 years (since the 1987 Superstition Hills and Elmore Ranch sequence).

Characteristics

The San Jacinto Fault Zone and the San Andreas Fault (SAF) accommodate up to 80% of the slip rate between the North American and Pacific plates. The extreme southern portion of the SAF has experienced two moderate events in historical times, while the SJFZ is one of California's most active fault zones and has repeatedly produced both moderate and large events. The locations of earthquakes before the 1954 Arroyo Salada earthquake are not precisely known, but the events' effects place them on the SJFZ and not on the SAF. The 1923 North San Jacinto Fault earthquake struck the Inland Empire area of southern California at a time of relatively low population, and a repeat event in modern times would result in heavy property damage and loss of life. [1]

SegmentLengthLast rupture
San Bernardino35 km1890
San Jacinto42 km1918
Anza90 km1750
Coyote Creek40 km1892
Borrego Mtn29 km1968
Superstition Mtn23 km1430
Superstition Hills22 km1987
WGCEP 1995, pp. 386, 387

Segments

A 1995 report by the Working Group on California Earthquake Probabilities identified seven individual segments of the SJFZ. The group consisted of more than three dozen seismologists, including Keiiti Aki and C. Allin Cornell, and was organized by the Southern California Earthquake Center for the USGS and the California Office of Emergency Services. The 1995 paper was the third in a series of reports that was set in motion following the 1992 Landers earthquake in southern California with the intention of updating the data and the approach for calculating the probabilities for large earthquakes along the southern San Andreas and San Jacinto Fault zones. Both these fault zones were grouped together as having adequate paleoseismic data to assign conditional probabilities for future damaging earthquakes. [2]

The original Working Group in 1988 had identified five segments of the fault zone. From north to south, the segments were labeled the San Bernardino Valley, San Jacinto Valley, Anza, Borrego Mountain, and Superstition Hills. The 1995 group then added the Coyote Creek and Superstition Mountain segments, defined the Anza segment to include the Clark and Casa Loma faults, and updated the slip rates for each segment. The three northern sections (San Bernardino, San Jacinto, and Anza) were assigned 12 mm per year of slip and the four remaining sections were given 4 mm of slip, and error rates were half the total estimated slip for each segment (±6 mm and ±2 mm respectively) with the exception of the Anza segment which had slightly exaggerated rates of +7 mm and −5 mm. [3]

Thirty year probabilities for segment-rupturing earthquakes were estimated using three separate models then a preferred weighted result was presented for each segment. While the San Bernardino (37%) and San Jacinto (43%) segments both saw large increases since the 1988 report, due in part to increased estimates for slip rates and decreased estimates for inherent displacement, the Anza segment (17%) was determined to have a decreased probability, based on an increased segment length. The Coyote Creek (18%), Superstition Mountain (9%), and Superstition Hills (2%) segments received first time estimates (none were assigned in 1988) and the Borrego Mountain segment received a more specific value of 6%. [4]

San Bernardino Valley

California Coast, Los Angeles to San Diego Bay. Overlaid lines on this NASA photo (2008) identify the San Jacinto Fault Zone (right) parallel to the Elsinore Fault (left) SoCal Coast.jpg
California Coast, Los Angeles to San Diego Bay. Overlaid lines on this NASA photo (2008) identify the San Jacinto Fault Zone (right) parallel to the Elsinore Fault (left)

The northernmost primary strand of the SJFZ is the Claremont strand (though subsidiary parallel strands exist). It spans a total of 75 km (47 mi), from its northern endpoint in Cajon Pass to its southern endpoint in the San Jacinto Valley. Within the San Bernardino Valley itself, the SJFZ approaches or intersects the right-lateral strike-slip San Andreas Fault to the north, the oblique normal Crafton Hills Fault Zone to the east, and the Cucamonga Thrust to the west. A series of moderate earthquakes affected this area in the 1890s, though it is uncertain how many of these occurred specifically on the SJFZ. The Claremont strand has not had a major earthquake in the instrumental period, but paleoseismology indicates that its last surface rupturing event occurred in the early 19th century, and that comparable earthquakes occur on average of every 160 to 220 years. [5]

San Jacinto Valley

The San Jacinto Valley is a 25 km long, ~4 km wide valley that was formed by extension in a region of overlap between two major parallel strands of the SJFZ. The valley is bounded by the Claremont strand to the northwest (see above) and the 25 km long Casa Loma strand to the southeast. The Clark strand, which is separated from the Casa Loma by a small compressional step in the city of Hemet, continues southeastward out of the valley. This area was heavily damaged by the historic earthquakes of 1899 and 1918. The 1899 event is thought to have occurred within the valley, likely on the Casa Loma strand, while the 1918 event has been identified on the Clark strand between Hemet and Anza. [6]

Anza

While the 1988 Working Group included the Clark, Coyote Creek, and Buck Ridge faults, the 1995 Working Group limited the segment to just the 90 km (56 mi) Clark fault. A paleoseismic investigation on this segment at Hog Lake indicated three historical surface-rupturing events occurred around 1210, 1530, and 1750 with an average recurrence period for a magnitude 7.0–7.5 earthquake of 250 years. [7]

Coyote Creek

With a recurrence period of 175 (+158 / -95) years, no surface-rupturing event has occurred on this 40 km (25 mi) segment since 1892. [7]

Borrego Mountain

The extent of this segment is based on the surface rupture of the 1968 Borrego Mountain earthquake and shares a recurrence interval of 175 years. [7]

Superstition Hills

The 1988 Working Group defined the segment as two parallel strands, the Superstition Hills and Superstition Mountain faults, though no slip rate or recurrence interval was known. On November 23, 1987, the Working Group determined that the available information was still not adequate to assign 30-year probabilities. On November 24, 1987, the fault ruptured, along with an unknown fault (later named the Elmore Ranch fault). Kenneth W. Hudnut and Kerry Sieh examined the surface rupture (along with a trench investigation) in 1989 and estimated the slip rate for the prior 330 years to be 2 – 6 mm/yr (±1 mm). The Working Group used these new figures to assign a slip rate of 4 ±2 mm/yr with an average recurrence interval of 250 (+400 / -133) years for the segment. [7] [8]

Superstition Mountains

Three surface-faulting events were found to have occurred along this newly added segment. A trench investigation by Larry Gurrola and Thomas Rockwell near the north shore of ancient Lake Cahuilla dated the events to 885–1440. The slip rate for the Borrego mountain segment (4 ± 2mm/yr) was extrapolated for use along the segment and a recurrence interval of 340 years was established. [7]

Anza seismic gap

With at least six and as many as ten large events since 1890, the right-lateral strike-slip SJFZ is southern California's most restless fault, with the exception of several sections which have seen less frequent activity. In a 1975 study, one of these (a 40 km (25 mi) stretch) was labeled the "Anza to Coyote Mountain slip gap", and was further refined in a 1984 paper by seismologists Christopher Sanders and Hiroo Kanamori to include only a smaller 20 km (12 mi) section near the town of Anza. By studying several moderate events (and their aftershocks) that occurred in 1967 (4.7L), 1975 (4.8L), and 1980 (5.5L), Sanders and Kanamori determined the seismogenic but locked nature of the gap. Were the entire fault segment to rupture in a single event, this newly modified length limited the potential of the segment to generate a magnitude 6.5 earthquake, similar in size to previous events along the SJFZ. However, if the slip were to extend out of the Anza area, the earthquake could be up to, but not larger than 7.0 in magnitude. [9]

At least six large ruptures of the San Jacinto Fault Zone are known to have followed the 1857 Fort Tejon earthquake that ruptured the central segment of the San Andreas Fault. These events began with the 1899 San Jacinto earthquake and occurred at intermittent intervals culminating with the 1987 Superstition Hills and Elmore Ranch events. The 1857 rupture spanned a total of 360 kilometers (220 mi) and terminated on the southeast end near the point where the San Jacinto Fault Zone branches away from the San Andreas Fault Zone at the Cajon Pass. In a paper published in the journal Science , Christopher Sanders plotted the earthquakes of the SJFZ by time and location and found that a uniform pattern became apparent. Moving southeastward from the Cajon Pass, the large SJFZ events appear on a line with a slope of 1.7 km per year and Sanders hypothesized that the 1857 earthquake introduced a strain pulse that migrated southeast and triggered large earthquakes as it traversed the SJFZ at that rate. [10]

Earthquakes

USGS Shakemap - 1968 Borrego Mountain earthquake.jpg
USGS Shakemap - 1987 Superstition Hills earthquake.jpg
USGS ShakeMaps for the 1968 Borrego Mountain earthquake (left) and the second (stronger) mainshock in the November 1987 sequence

1812 San Juan Capistrano earthquake

Uncertainty surrounds the details of this earthquake but recent studies suggest that a joint rupture of both the SAF and the San Jacinto Fault Zone to the southeast more closely match the damage pattern recorded about this event. [11] [12]

1899 San Jacinto earthquake

On December 25, with a maximum intensity of MM IX, this magnitude 6.6 earthquake destroyed San Jacinto and Hemet and six were killed by adobe walls that collapsed at Soboba (just east of San Jacinto). A 46 m (151 ft) fissure, which may have been surface rupture of the San Jacinto Fault, ran under a house that was severely damaged near Hemet. [13] The effects of the early morning earthquake were severe. Not all the buildings in San Jacinto were completely destroyed by the thirty seconds of shaking, but most of the brick buildings' second floors were heavily damaged. [14] ( 33°48′N117°00′W / 33.8°N 117.0°W / 33.8; -117.0 )

1968 Borrego Mountain earthquake

On April 9, a magnitude 6.4 ML earthquake with a maximum perceived intensity of MM VII hit the extreme eastern San Diego County area and created a 31 km (19 mi) surface break along the Coyote Creek Fault. California State Route 78 was damaged with cracks near Ocotillo Wells and large boulders blocked the Montezuma-Borrego Springs Highway. Other rockslides occurred at Palm Canyon and Split Mountain in Anza-Borrego Desert State Park. One house was split apart in Ocotillo Wells with one bedroom becoming detached from the rest of the home. The mainshock was felt in Arizona and Nevada and the largest aftershock damaged a theater's walls in Calexico near the Mexico–United States border. [15]

According to a report in the Los Angeles Times , this was the strongest earthquake to affect southern California since the Tehachapi earthquake fifteen years earlier. Taller buildings swayed in both Los Angeles and San Diego and power outages affected numerous areas, primarily in the cities of Imperial Valley. Power failures along with disruption to telephone service caused problems in the Hemet Valley area, and smaller power outages in Los Angeles and Orange Counties also occurred. A brick wall collapsed at a laundromat in Westmorland (in the El Centro Metropolitan Area) but no one was injured, and in the seaside neighborhoods of San Diego county several hundred windows were broken. Charles Richter, a Caltech seismologist, stated that the earthquake was centered near Ocotillo Wells about 120 mi (190 km) southeast of Los Angeles. The mainshock occurred at 6:28 pm and aftershocks continued through the evening, but were tapering off by 10 pm. [16] ( 33°12′N116°06′W / 33.2°N 116.1°W / 33.2; -116.1 )

1987 Superstition Hills earthquakes

Two earthquakes in late November caused property damage totaling three million in Imperial County. The two events were separated by eleven hours and were located in the western Imperial Valley on the Superstition Hills Fault and a previously unknown fault. Damage in Westmoreland, Imperial, and El Centro consisted of collapsed chimneys, broken windows, and damaged highways. The Worthington Road bridge, at the New River, failed due to liquefaction and at the Desert Test Range Control Center, water tanks toppled into the building and other equipment crashed through a window. Activities were suspended there for several days due to the damage. The Southern California Irrigation District estimated damage to be $600,000 – $750,000. The initial shock produced a small amount of deformation in the canal's liner while the second main shock caused considerable damage to thousands of feet of canal lining in the northwest section of the valley. [17]

Several foreshocks preceded the main shocks and a series of aftershocks included two in the range of magnitude five. On the Mexican side of the border, 50 injuries and two deaths were reported, and 44 were treated for their injuries in California. According to the spokesperson for the state of Baja California, a motor vehicle accident east of Mexicali that claimed the lives of a mother and her four-year-old son was blamed on the earthquake. Thomas H. Heaton, a USGS seismologist, stated that the faults in the area are difficult to track down because of the sediment deposited in the valley, which had been an intermittent drainage basin of the Colorado River. [18]

The Superstition Hills fault (SHF) lies between the Coyote Creek fault that ruptured during the 1968 event and the Imperial Fault that ruptured during the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake. To the northeast are several cross faults that trend northeast. One of these faults ruptured during a large aftershock of the 1979 event and another slipped as the smaller of the two shocks during the November 1987 sequence. The first shock (on what became known as the Elmore Ranch fault) measured 6.2 Ms and the shock 11.4 hours later on the SHF measured 6.6 Ms. [19] ( 33°06′N115°48′W / 33.1°N 115.8°W / 33.1; -115.8 & 33°00′N115°48′W / 33.0°N 115.8°W / 33.0; -115.8 )

See also

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<span class="mw-page-title-main">Parkfield earthquake</span> Series of earthquakes in California, US

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 on the fault at unusually regular intervals, between 12 and 32 years apart, between 1857 and 1966. The latest major earthquake in the region struck on September 28, 2004.

The 1857 Fort Tejon earthquake occurred at about 8:20 a.m. on January 9 in central and Southern California. One of the largest recorded earthquakes in the United States, with an estimated moment magnitude of 7.9, it ruptured the southern part of the San Andreas Fault for a length of about 225 miles, between Parkfield and Wrightwood.

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 in the Imperial Valley, causing widespread damage to irrigation systems and killing nine people.

<span class="mw-page-title-main">Wairau Fault</span> Active fault in New Zealand

The Wairau Fault is an active dextral strike-slip fault in the northeastern part of South Island, New Zealand. It forms part of the Marlborough Fault System, which accommodates the transfer of displacement along the oblique convergent boundary between the Indo-Australian Plate and Pacific Plate, from the transform Alpine Fault to the Hikurangi Trough subduction zone.

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 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 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.

<span class="mw-page-title-main">1918 San Jacinto earthquake</span> Earthquake in Southern California

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 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 1987 Superstition Hills earthquake affected the Imperial Valley of California and Baja California on November 24, nearly 12 hours after a Mw 6.0 foreshock, called the Elmore Ranch earthquake. The mainshock, measuring Mw 6.5, struck at 17:54 PST, along the Superstition Hills segment of the San Jacinto Fault Zone. The earthquake generated a 27 km (17 mi) surface rupture with additional postseismic slip continuing for a year.

The 1968 Borrego Mountain earthquake occurred on April 8, at 18:28 PST in the geologically active Salton Trough of Southern California. The Salton Trough represents a pull-apart basin formed by movements along major faults. This region is dominated by major strike-slip faults one of them being the San Jacinto Fault which produced the 1968 earthquake. The mainshock's epicenter was 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). The zone of surface rupture was assigned a maximum Modified Mercalli intensity (MMI) of VII.

The 1899 San Jacinto earthquake occurred on Christmas morning at 04:25 local time in Southern California. The estimated moment magnitude 6.7 earthquake had an epicenter located 10 miles southeast of San Jacinto. The earthquake had a maximum Mercalli intensity of IX (Violent). Severe damage occurred, amounting to US$50,000, as well as six fatalities.

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.

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.

<span class="mw-page-title-main">San Diego Trough Fault Zone</span> Group of strike-slip faults along the coast of California

The San Diego Trough Fault Zone is a group of connected right-lateral strike-slip faults that run parallel to the coast of Southern California, United States, for 150–166 km (93–103 mi). The fault zone takes up 25% of the slip within the Inner Continental Borderlands. Portions of the fault get within 30 km (19 mi) of populated cities; however, the faults never reach shore. The north of the fault zone begins where the San Pedro Basin Fault Zone and the Santa Catalina Fault Zone meet, and the southern section terminates where it reaches the Bahía Soledad Fault. Seismic risk along the fault is high, with potential earthquake scenarios reaching up to magnitude 7.9 in the worst case. An earthquake of this size would devastate coastal areas.

References

Notes

  1. ↑ Yeats, R. (2012), Active Faults of the World, Cambridge University Press, pp. 102, 103, ISBN   978-0521190855
  2. ↑ Working Group on California Earthquake Probabilities 1995 , p. 379
  3. ↑ Working Group on California Earthquake Probabilities 1995 , pp. 383, 385
  4. ↑ Working Group on California Earthquake Probabilities 1995 , pp. 386, 387
  5. ↑ Onderdonk, N. W.; Rockwell, T. K.; McGill, S.; Marliyani, G. I. (2013), "Evidence for seven surface ruptures in the past 1600 years on the Claremont Fault at Mystic Lake, northern San Jacinto Fault Zone", Bulletin of the Seismological Society of America, 103 (1), Seismological Society of America: 519–541, Bibcode:2013BuSSA.103..519O, doi:10.1785/0120120060
  6. ↑ Salisbury, J. B.; Rockwell, T. K.; Middleton, T. J.; Hudnut, K. W. (2012), "LiDAR and Field Observations of Slip Distribution for the Most Recent Surface Ruptures along the Central San Jacinto Fault", Bulletin of the Seismological Society of America, 102 (2), Seismological Society of America: 598–619, Bibcode:2012BuSSA.102..598S, doi:10.1785/0120110068
  7. 1 2 3 4 5 Working Group on California Earthquake Probabilities 1995 , pp. 429–431
  8. ↑ Hudnut & Sieh 1989 , p. 325
  9. ↑ Sanders & Kanamori 1984 , pp. 5873, 5881–5882, 5877, 5889
  10. ↑ Sanders, C. O. (1993), "Interaction of the San Jacinto and San Andreas fault zones, Southern California: triggered earthquake migration and coupled recurrence intervals", Science , 260 (5110), American Association for the Advancement of Science: 973–976, Bibcode:1993Sci...260..973S, doi:10.1126/science.260.5110.973, PMID   17818388
  11. ↑ "Research Reveals a Dual Fault Threat | ASCE". 2017-07-02. Archived from the original on 2017-07-02. Retrieved 2019-05-16.
  12. ↑ Lozos, Julian C. (2016-03-01). "A case for historic joint rupture of the San Andreas and San Jacinto faults". Science Advances. 2 (3): e1500621. Bibcode:2016SciA....2E0621L. doi:10.1126/sciadv.1500621. ISSN   2375-2548. PMC   4803493 . PMID   27034977.
  13. ↑ Stover & Coffman 1993 , pp. 74, 113
  14. ↑ Townley 1918 , p. 61
  15. ↑ Stover & Coffman 1993 , pp. 91, 154
  16. ↑ Main, Dick (April 9, 1968). "Quake Jolts L.A.; Much of Southwest Feels Shocks; Most Violent Temblor Since 1952 Makes Buildings Sway". Los Angeles Times.
  17. ↑ Stover & Coffman 1993 , pp. 98, 179–180
  18. ↑ Mathews, Jay (November 25, 1987). "2 Dead, Scores Injured in California Quakes; Some Buildings Damaged in Imperial Valley". The Washington Post. Archived from the original on September 24, 2015. Retrieved November 22, 2012.(subscription required)
  19. ↑ Hudnut & Sieh 1989 , pp. 304, 305

Sources

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