1989 Loma Prieta earthquake

1989 Loma Prieta earthquake
Image of collapsed Cypress Street Viaduct in Oakland, California
1989 Loma Prieta earthquake is located in California
Santa Cruz
Santa Cruz
Oakland
Oakland
Salinas
Salinas
1989 Loma Prieta earthquake
UTC time1989-10-18 00:04:14
ISC event389808
USGS-ANSSComCat
Local dateOctober 17, 1989 (1989-10-17)
Local time17:04:15 PDT[1]
Duration8–15 seconds[2]
Magnitude6.9 Mw, 7.2 MS [3]
Depth19 km (12 mi)[4]
Epicenter37°02′N 121°53′W / 37.04°N 121.88°W / 37.04; -121.88[1]
TypeOblique-slip reverse
Areas affectedCentral Coast (California)
San Francisco Bay Area
United States
Total damage$5.6–6 billion[1][5] (equivalent to $13.8–14.7 billion today)
Max. intensityMMI IX (Violent)[1]
Peak acceleration0.65 g (at epicenter)[2]
TsunamiYes[6][7]
Landslides1,000–4,000[1][2]
Foreshocks5.3 ML June 27, 1988[8]
5.4 ML August 8, 1989[8]
Casualties63 killed, 3,757 injured[1][9]

On October 17, 1989, at 5:04 p.m. local time, the Loma Prieta earthquake occurred at the Central Coast of California. The shock was centered in The Forest of Nisene Marks State Park in Santa Cruz County, approximately 10 mi (16 km) northeast of Santa Cruz on a section of the San Andreas Fault System and was named for the nearby Loma Prieta Peak in the Santa Cruz Mountains. With an Mw magnitude of 6.9[10] and a maximum Modified Mercalli intensity of IX (Violent), the shock was responsible for 63 deaths and 3,757 injuries. The Loma Prieta segment of the San Andreas Fault System had been relatively inactive since the 1906 San Francisco earthquake (to the degree that it was designated a seismic gap) until two moderate foreshocks occurred in June 1988 and again in August 1989.

Damage was heavy in Santa Cruz County and less so to the south in Monterey County, but effects extended well to the north into the San Francisco Bay Area, both on the San Francisco Peninsula and across the bay in Oakland. No surface faulting occurred, though many other ground failures and landslides were present, especially in the Summit area of the Santa Cruz Mountains. Liquefaction was also a significant issue, especially in the heavily damaged Marina District of San Francisco, but its effects were also seen in the East Bay, and near the shore of Monterey Bay, where a non-destructive tsunami was also observed.[11]

Because it happened during a national live broadcast of the 1989 World Series, the annual championship series of Major League Baseball, taking place between Bay Area teams San Francisco Giants and the Oakland Athletics, it is sometimes referred to as the "World Series earthquake", with the championship games of the year being referred to as the "Earthquake Series". Rush-hour traffic on the Bay Area freeways was much lighter than normal because the game, being played at Candlestick Park in San Francisco, was about to begin, and this may have prevented a larger loss of life, as several of the Bay Area's major transportation structures suffered catastrophic failures. The collapse of a section of the double-deck Nimitz Freeway in Oakland was the site of the largest number of casualties for the event, but the collapse of human-made structures and other related accidents contributed to casualties occurring in San Francisco, Los Gatos, and Santa Cruz.

  1. ^ a b c d e f Cite error: The named reference Stover was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Clough was invoked but never defined (see the help page).
  3. ^ International Seismological Centre. ISC-EHB Bulletin. Thatcham, United Kingdom. [Event 389808].
  4. ^ ISC-EHB Event 389808 [IRIS].
  5. ^ Housner 1990, pp. 19–23
  6. ^ Cite error: The named reference Ma was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Breaker was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Perfettini was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Bolt was invoked but never defined (see the help page).
  10. ^ ANSS: Loma Prieta 1989, Origin (accessed 2019-04-01).
  11. ^ Ma, Kuo-Fong; Satake, Kenji; Kanamori, Hiroo (1991). "The origin of the tsunami excited by the 1989 Loma Prieta Earthquake  – Faulting or slumping?". Geophysical Research Letters. 18 (4): 637–640. Bibcode:1991GeoRL..18..637M. doi:10.1029/91GL00818. Retrieved November 3, 2020.