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1857 Fort Tejon earthquake

From Wikipedia, the free encyclopedia

1857 Fort Tejon earthquake
1857 Fort Tejon earthquake is located in California
Parkfield
Parkfield
Monterey
Monterey
Los Angeles
Los Angeles
Fort Tejon
Fort Tejon
1857 Fort Tejon earthquake
Local date January 9, 1857 (1857-01-09)
Local time08:20
Duration1–3 minutes[1]
Magnitude7.9 Mw[1][2]
Depth< 10 kilometers
Epicenter35°42′N 120°18′W / 35.7°N 120.3°W / 35.7; -120.3[1]
FaultSan Andreas Fault
TypeStrike-slip
Areas affectedCentral California
Southern California
United States
Total damageSevere[3]
Max. intensityIX (Violent)[4]
Casualties2 killed[5]

The 1857 Fort Tejon earthquake occurred at about 8:20 a.m. (Pacific time) on January 9 in central and Southern California. One of the largest recorded earthquakes in the United States,[6] 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 (350 kilometers), between Parkfield and Wrightwood.

Though the shock was centered near Parkfield, the event is referred to as the Fort Tejon earthquake, because that was the location of the greatest damage. Fort Tejon is just north of the junction of the San Andreas and Garlock Faults, where the Tehachapi, San Emigdio, and Sierra Pelona Transverse Ranges come together.

The earthquake is the most recent large event to occur along that portion of the San Andreas Fault, and is estimated to have had a maximum perceived intensity of IX (Violent) on the Modified Mercalli scale (MM) near Fort Tejon in the Tehachapi Mountains, and along the San Andreas Fault from Mil Potrero (near Pine Mountain Club) in the San Emigdio Mountains to Lake Hughes in the Sierra Pelona Mountains. Accounts of the events' effects varied widely, including the time of the main shock as well as foreshocks that occurred at several locations earlier in the morning.

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Transcription

Earthquakes occur when two blocks of rock below the Earth’s surface rub against each other. Where that tension happens underground is called the hypocenter, and up above we call that the epicenter. A little rumble could be the start of bigger things to come. They are called foreshocks. The bigger shocks that come after are called the main-shocks, which might be followed by after-shocks that could come a day after or many years after. We measure the power of an Earthquake from 1-10, judging its vibrations, or magnitude, on what we call a seismograph. Hundreds of small Earthquakes happen every day, but thankfully the huge ones are rare. A 9.5 magnitude earthquake in Chile was the most powerful ever recorded, but scientists say a 10 is possible. Today we’ll focus mostly on one country, in this episode of the Infographics Show, Biggest Earthquakes Ever - What Would It Take To Destroy The USA? Don’t forget to subscribe and click the bell button so that you can be part of our Notification Squad. We will first put into perspective Earthquakes in the USA when measured against quite recent earthquakes that were some of the largest in recorded history. Number three on the list of worst ever recorded earthquakes is one many of us old enough to remember could never forget: The 2004 Indian Ocean earthquake, sometimes called the Christmas tsunami due to when it took place and the ensuing tidal destruction. This undersea megathrust earthquake measured 9.1 – 9.3, creating tsunamis up to 100 ft high (30 meters), that quickly and devastatingly encroached coastal areas in 14 countries. 230,000–280,000 people were killed in all, from fishing villages on the western coast of Sri Lanka to touristy hotspots in Thailand’s beach towns. Number four on the list of worst ever recorded earthquakes is Japan’s 2011 Great East Japan Earthquake. This too triggered a massive tsunami reaching up to 133 feet in height (40.5 meters). It measured 9-9.1. Casualties were fewer in number than the aforementioned disaster – 15,894 deaths – much in part due to Japan’s infrastructure and the fact that Japan had superior warning systems. Many of the countries hit by the Asian tsunami had no idea what was coming their way, as can be seen in videos of tourists in Thailand still hanging out on the beach as the tsunami approaches. The USA is up there as having experienced one of the worst Earthquakes ever, second on the list of worst ever regarding magnitude. It was the 1964 Alaskan earthquake. It too caused great damage to structures, and generated its own tsunami, but the death toll at 139 was relatively small. Some of those deaths were as far away as California and Oregon, with loss of life not accorded to the Earthquake itself but the resultant tsunamis. While fatalities were low, the Earthquake caused wide fissures in roads and forests, destroyed many buildings, brought down bridges, and wrecked rail tracks. Had that happened in a densely populated metropolis, it could have been devastating. Well, one of the USA’s most populated places are the cities and surrounding areas of Los Angeles and San Francisco. According to the U.S. Geological Survey, the US is destined to meet with a large Earthquake in the not too distant future, and it could well be those areas where it happens. The worst Earthquake on record in the USA did indeed happen in San Francisco, in the year 1906. The 7.9 magnitude beast occurred along 300 miles of what’s called the San Andreas Fault. This is a 750 mile long (1,200 kilometers) tectonic boundary that separates the Pacific Plate and the North American Plate. The earthquake brought the city to ruins, collapsing structures and causing widespread fires. It’s thought that about 3,000 people died and of course many more were injured. 28,000 buildings were destroyed in total, and 250,000 San Franciscans lost their homes. This was without doubt the worst Californian earthquake in terms of causalities and destruction to buildings, but it wasn’t the most powerful. That was the Fort Tejon quake of 1857, that measured 7.9 in magnitude. Apparently only one person died when his house collapsed on him. Lesser quakes in the area have had a much more devastating effect. In fact, outside of Alaska, Hawaii, South Carolina and Idaho, all of the USA’s worst earthquakes in terms of damage done have been in California. Some of them happened not that long ago. Shortly after the San Francisco disaster came the Long Beach earthquake in 1933. It only had a magnitude of 6.4 but still claimed around 120 lives as people ran from collapsing buildings. The state was criticized for not having strong enough buildings to ensure safety, and as a result the state revised building codes. Some say it was a lucky escape since over 230 school buildings were destroyed, but as it happened close to 6pm, kids had already left the buildings. Building codes were once again revised after the 1971 San Fernando earthquake. It measured 6.7 in magnitude, and caused damage to many buildings in districts of Los Angeles and beyond. It’s thought that around 58–65 people lost their lives. 49 of them were in one building alone: the Olive View Hospital in Sylmar. One of the survivors recalled some years after the incident, “There was relief when the shaking stopped, but there were still sounds of crunching…And groans.” The worrying thing is the hospital was built with earthquake resistance in mind. Following this in 1989 and 1994, California experienced two more earthquakes resulting in loss of life. The 1989 Loma Prieta 6.9 earthquake was the first deadly earthquake to hit San Francisco Bay since the 1906 disaster, and it took 63 lives. Most of those people succumbed to a collapsed highway in Oakland. The ’94 quake hit Northridge in Southern California and measured 6.7. 60 people died, this time because their houses were structurally weak. When scientists are asked which large cities are the mostly likely to be hit by a big earthquake in the next 20 or 30 years, one that measures over 6.7, places in California are high on the list. The world’s largest most populated city, Tokyo, is also up there. As we write this, just recently a 7.1 magnitude earthquake hit central Mexico, causing buildings to collapse in the densely populated capital of Mexico City. The full death toll is expected to be more than the 216 that has already been reported. But the question we ask today, is what would it take to destroy entire cities in the USA or even destroy the country? First of all, scientists say what we already know from this show so far, that the worst earthquakes that could hit the USA would very likely be in Alaska or in California. The scientists say one of the worse places is the Cascadia Subduction Zone – the coast from California all the way up to Canada. They believe a 9.0 magnitude quake is very much possible, and if one happened of this size in this coastal region, it would generate huge tsunamis that would envelop the American west coast. The last one happened in 1700, and they believe we are due for another anytime in the next 400 years. According to Live Science, even though the San Andreas Fault is seen as a more dangerous area, it is thought a quake of more than 8.0 is unlikely. Former US Geological Survey scientist, Jim Berkland, who once had a book written about him called ‘The Man Who Predicts Earthquakes’, has gone on record stating the one of these regions is due for a “Big One” soon. He has been right a few times in the past. While California has taken the headlines for a long time regarding mass destruction by earthquakes, more recent reports suggest that the Mid-West could also be an accident waiting to happen. In 1811 and 1812, a quake of 7.5 magnitude occured along the New Madrid Seismic Zone in New Madrid, Missouri. That was once thought to be a one off, but now science tells us it could happen again. This could potentially wreak havoc in Missouri, Mississippi, Illinois, Indiana, Arkansas, Kentucky, and Tennessee. A large city such as New York has suffered minor earthquakes in the past, but as it doesn’t sit on any major fault line, it’s unlikely to experience a big quake. Its biggest ever was in 1884 and measured 5.3, and some media suggest another is on its way. In fact, according to the U.S. Geological Survey, 42 of the 50 states will likely experience a damaging Earthquake in the next 50 years, but none so threatening as the one expected in the Sunshine State. Less reputable media have reported on a mega-quake that could rip apart the US and kill millions, but so far science is not backing that up. According to The Smithsonian, the all-out destruction depicted in the movie San Andreas is way more fiction than fact. If something big goes down, the magazine says that “even the largest of California's quakes won’t be felt by anything but seismometers on the East Coast.” A scientist did say, though, that when the big one comes, and it will, it will likely unleash destruction on many levels. It’s thought that roughly 2,000 people will die, and a lot of the damage will come from fires. Be prepared said another scientist. “Everyone should live every day like it could be the day of the Big One,” he said. “Because any day, even today, could be that day.” So, where do you think the next big earthquake will hit? Have you ever experienced an earthquake? Let us know in the comments! Also, be sure to check out our other video called American Behaviors Considered Rude in Other Countries?! Thanks for watching, and, as always, don’t forget to like, share, and subscribe. See you next time!

Contents

Tectonic setting

The 1857 earthquake ruptured about 350 kilometers (220 mi) of the southern part of the San Andreas Fault, the structure that accommodates most of the displacement along the transform boundary between the North American Plate and the Pacific Plate. The Pacific Plate is moving north relative to the Sierra Nevada-Great Valley Block of the North American Plate at about 38 millimeters (1.5 in) per year.[7] The displacement rate along the various sections that ruptured is 34 millimeters (1.3 in) per year along the Parkfield, Cholame, Carrizo and Big Bend sections and 27 millimeters (1.1 in) and 29 millimeters (1.1 in) per year along the Mojave north and Mojave south sections.[8] Paleoseismic studies have found evidence for many prehistoric earthquakes in the last 3,000 years on this part of the San Andreas Fault.[9]

Earthquake

The earthquake ruptured a substantial portion of the southern San Andreas fault, but not the entire length. Thomas H. Jordan, director of the Southern California Earthquake Center, stated that the slip likely stopped in the area near Cajon Pass, perhaps because the tectonic stresses on that part of the fault had been released several decades earlier during the 1812 Wrightwood earthquake.[10] The average slip along the fault was 4.5 meters (15 ft), and a maximum offset of 6 meters (20 ft) was recorded in the Carrizo Plain area in southeastern San Luis Obispo County.[11] [12] With an estimated magnitude of 7.9, this was the last "Big One" in Southern California. The extreme southernmost portion of the San Andreas fault, which terminates near Bombay Beach at the Salton Sea, last ruptured in 1680.[2]

Surface faulting may have extended beyond the boundaries of the regularly acknowledged slip length. Researchers recorded first and second-hand accounts of the ground crack, which was understood to be recent surface faulting and not just the topography of the existing rift. On the extreme northern end of the rupture zone, the surface cracking extended 80 kilometers (50 mi) north of Cholame into San Benito County. On the southern end, the population centers were not as close to the fault, and early observers were probably limited to the stretch of the fault between Fort Tejon and Elizabeth Lake, as that was close to the Stockton – Los Angeles Road, the primary inland north−south route then.[13]

Evidence of uprooted and displaced trees south of Elizabeth Lake indicates surface faulting along a mole track (an "array of en echelon primary Riedel shears with linking compressional rolls and minor thrusts")[14] that ran directly under three Jeffrey Pines. Two of the three trees examined were tilted in their lower extremity, while the upper portions remained relatively untilted. Tree ring dating confirmed that the trees had originated 10 and 25 years before 1857 and also that the rings began to grow twice as thick on the side in the direction of the tilt. This is a frequently noted compensation of tree tilt. Seismologist Kerry Sieh determined that fault slip and the associated ground disturbance was the source of the mole track and subsequent tree tilt.[13]

Foreshocks

An isoseismal map for the main shock
An isoseismal map for the main shock

Various accounts of the event indicate the presence of foreshocks between one and nine hours before the main event,[15] and based on the (uncertain) distribution of those shocks, it is assumed that the beginning of the fault rupture (the epicenter) was in the area between Parkfield and Cholame, about 97 kilometers (60 mi) northwest.[16]

The lack of standardized timekeeping during this period of California's history contributed to some of the inaccurate reports of when the pre-shocks occurred. Local solar time was being used in 1857 and San Francisco would have been the locality with the most accurate time kept as it was a center of commerce and other activity. Standard time was not followed until the 1880s, with the Pacific Time Zone being aligned with the 120th meridian. The differences in local times were substantial, with San Francisco at 122.43 W and San Diego at 117.10 W, the difference between the two would be around 22 minutes (4 minutes per degree).[17] At least one individual reported foreshock times that varied by as much as half an hour when speaking to two different newspapers.[18]

The firsthand reports were most abundant for the shocks felt at 1, 2, and 4 hours before the main shock which were later labeled the predawn, dawn, and sunrise shocks. The predawn event shook residents of San Francisco (MM II – III), San Jose (MM IV), and Santa Cruz (MM IV). The dawn shock was felt in those locales plus Fort Tejon and possibly the Carrizo Plain. The sunrise shock was felt in San Francisco (MM III), Monterey (MM IV), and Visalia (MM II – III). Sacramento and Los Angeles did not report any of these events.[19]

Several mid-twentieth-century earthquakes had similar felt reports to the dawn and sunrise shocks and with close inspection, Sieh theorizes that both events were local to coastal central California, probably between Point Conception and Monterey. Also, during that period, no central California earthquake with a magnitude of less than five had a felt area as large as the two foreshocks, while events larger than magnitude six have had "somewhat larger" felt areas, so it could be said that the foreshocks most likely were between magnitude five and six.[20]

Parkfield earthquakes occurred with exceptionally regular intervals (between 20 and 30 years) between 1857 and 1966.[21] Sieh studied four of these events (1901, 1922, 1934, and 1966) and found that they helped to determine the southeast boundary for the origination of the dawn foreshock. The coverage and intensities of felt reports for that earthquake show a solid resemblance to the Parkfield events.[20] Only one of the four Parkfield events was not felt further southeast than the dawn shock, so Sieh concluded that if the San Andreas was the source of the event, then it was reasonable to assume that the Parkfield to Cholame stretch of the fault was responsible for producing the dawn felt intensities,[22] though the San Andreas is not the only possible source for the dawn event. For example, the November 22, 1952, magnitude six Bryson earthquake "nearly duplicates" the felt reports.[23] That event may have occurred west of the San Andreas on the Nacimiento fault, though the highest felt reports were along the Rinconada fault around 56 kilometers (35 mi) southwest of the San Andreas.

Damage

Most of the adobe buildings at Fort Tejon were badly damaged and several people were injured there. More buildings were destroyed along a twenty-mile stretch between Fort Tejon and southeast to Elizabeth Lake, a sag pond that was formed directly on the San Andreas fault. Streams and springs experienced disturbances in San Diego and Santa Barbara Counties, while the Kern River, Kern Lake, and Los Angeles River all spilled over their banks. Farther north in Santa Clara County the flow of well water was affected. Ground cracks from liquefaction of swampy ground were observed near the Pueblo de Los Angeles and in the Oxnard Plain, and ground fissures were reported near the Los Angeles, Santa Ana, and Santa Clara Rivers.[1]

Central and southern California were thinly populated at the time and this likely helped limit the damage from the earthquake, but the lack of people present also reduced the number of perspectives to use in determining intensity estimates. Areas with the highest population density like San Francisco, Stockton, and Los Angeles provided enough information about the effects of the earthquake to provide the best estimates of intensity. At downtown Los Angeles, with a maximum perceived intensity of VI, some homes and buildings were cracked, but no major damage was reported. In Ventura (MM VII) the roof of Mission San Buenaventura collapsed and the bell tower was damaged, and farther north, the front wall of the old adobe Mission Santa Cruz chapel collapsed. One of the two deaths reported included a woman who was killed by a collapsing adobe house in nearby Gorman, and an elderly man may have collapsed and died in the Los Angeles area as a result of the earthquake.[16][24][25]

Aftershocks

The mainshock was followed by a series of aftershocks that continued for at least 3.75 years, although the total number of large aftershocks was less than would be expected for an earthquake of this size. The four largest aftershocks all had magnitudes greater than 6, although there are large uncertainties in both location and magnitude due to the limited number of data points available. On the night of January 9 there was a large aftershock with an estimated magnitude of about 6.25, with a possible epicenter near the Garlock Fault. The largest aftershock occurred on the afternoon of January 16 with an estimated magnitude of about 6.7, with a possible offshore location,[26] and high felt intensities in Southern California communities. Santa Barbara and San Bernardino reported an MM intensity of V and Los Angeles reported V and VI.[17] Two significant events occurred in the San Bernardino area on December 15–16, 1858, with the latter having an estimated magnitude of about 6. The last recorded major aftershock occurred on April 16, 1860, with an estimated magnitude of about 6.3, with an epicenter close to the Parkfield section of the San Andreas Fault.[26]

Future threat

Scientists and public service officials have speculated on the threat of another very large earthquake occurring in southern California and what type and scale of damage might result. The portion of the fault that ruptured in 1857 has settled into a period of dormancy and this has given rise to suggestions that future slip along that zone may be characterized by a very large 1857-type event followed by another period of inactivity.[27] The communities of Frazier Park, Palmdale, and Wrightwood are all located very close to the San Andreas fault, though much of the Los Angeles area could be affected even at a greater distance from the rupture area if a similar event were to reoccur there. Swaminathan Krishnan, assistant professor of civil engineering and geophysics at the California Institute of Technology, said that if a similar rupture from Parkfield to Wrightwood were to happen again, it would severely affect the Los Angeles area, with the San Fernando Valley being particularly hard hit.[28]

The Los Angeles Aqueduct and California Aqueduct, two of the principal water transfer infrastructure systems supplying Greater Los Angeles, both cross the San Andreas fault within the main damage zone of the Fort Tejon earthquake, in the Tehachapi and Sierra Pelona Mountains.

See also

References

  1. ^ a b c d 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. 72, 101, 102
  2. ^ a b Jordan, Thomas (January 9, 2007). "Overdue and unprepared for the Big One". Los Angeles Times. Retrieved December 16, 2012.
  3. ^ National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
  4. ^ Agnew & Sieh 1978, p. 1722
  5. ^ Agnew & Sieh 1978, p. 1723
  6. ^ "Significant Earthquakes and Faults". California Institute of Technology. Retrieved March 6, 2018.
  7. ^ Bürgmann, R.; Hilley G., Ferretti A. & Novali F. (2006). "Resolving vertical tectonics in the San Francisco Bay Area from permanent scatterer InSAR and GPS analysis" (PDF). Geology. 34 (3): 221–224. Bibcode:2006Geo....34..221B. doi:10.1130/G22064.1.
  8. ^ Wills, C. J.; Weldon II R. J. & Bryant W. A. (2008). "Appendix A: California Fault Parameters for the National Seismic Hazard Maps and Working Group on California Earthquake Probabilities 2007" (PDF). Open File Report 2007-1437. United States Geological Survey. pp. 5–19.
  9. ^ Scharer, K. M.; Biasi G. P., Weldon II R. J. & Fumal T. E. (2010). "Quasi-periodic recurrence of large earthquakes on the southern San Andreas fault". Geology. 38 (6): 555–558. Bibcode:2010Geo....38..555S. doi:10.1130/G30746.1.
  10. ^ Rong-Gong Lin II (October 8, 2010). "San Andreas fault capable of magnitude 8.1 earthquake over 340-mile swath of California, researchers say". Los Angeles Times. Retrieved April 1, 2012.
  11. ^ Zielke, O.; Arrowsmith, J. R.; Grant, L.; Akciz, S. O. (2012), "Slip in the 1857 and Earlier Large Earthquakes Along the Carrizo Plain, San Andreas Fault", Science, 327 (5969): 1119–1122, doi:10.1126/science.1182781] (inactive March 14, 2019), PMID 20093436
  12. ^ Zielke, O.; Arrowsmith, J. R.; Grant, L.; Akciz, S. O. (2012), "High‐Resolution Topography‐Derived Offsets along the 1857 Fort Tejon Earthquake Rupture Trace, San Andreas Fault", Bulletin of the Seismological Society of America, 102 (3): 1135–1154, doi:10.1785/0120110230
  13. ^ a b Sieh 1978a, p. 1424
  14. ^ Sibson R.H. (2003). "Thickness of the Seismic Slip Zone" (PDF). Bulletin of the Seismological Society of America. 93 (3): 1169–1178. Bibcode:2003BuSSA..93.1169S. doi:10.1785/0120020061.
  15. ^ Sieh 1978b, p. 1731
  16. ^ a b "Fort Tejon Earthquake". Southern California Earthquake Center. Archived from the original on October 18, 2013. Retrieved March 25, 2012.
  17. ^ a b Sieh 1978b, p. 1733
  18. ^ Sieh 1978b, pp. 1731–1735
  19. ^ Sieh 1978b, pp. 1735–1737
  20. ^ a b Sieh 1978b, p. 1737
  21. ^ Kerr, R. A. (September 28, 2004), "The Parkfield Earthquake, Finally", Science, American Association for the Advancement of Science
  22. ^ Sieh 1978b, pp. 1737, 1739, 1741–42
  23. ^ Sieh 1978b, p. 1742
  24. ^ Agnew & Sieh 1978, pp. 1721–1723
  25. ^ Kimbro, Edna E. "Construction Chronology of the Site of Holy Cross Church: Ex-Mission Santa Cruz became Holy Cross". Santa Cruz Public Libraries. Retrieved December 16, 2012.
  26. ^ a b Meltzner & Wald 1999, pp. 1117
  27. ^ Sieh 1978a, p. 1421
  28. ^ Bernstein, Sharon (January 10, 2007). "Past offers lessons on future Big One – Scientists begin a study of quake readiness by raising awareness of a massive temblor in 1857". Los Angeles Times. Retrieved March 28, 2012.

Bibliography

External links

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