That's not massive, this is massive.
https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake
1989 Loma Prieta earthquake
From Wikipedia, the free encyclopedia
Santa Cruz
Oakland
Salinas
UTC time
1989-10-18 00:04:14
ISC event
389808
USGS-ANSS
ComCat
Local date
October 17, 1989
Local time
5:04:15 p.m. PDT[1]
Duration
8–15 seconds[2]
Magnitude
Mw 6.9; MS 7.2 [3]
Depth
19 km (12 mi)[4]
Epicenter
37.04°N 121.88°W
Coordinates: 37.04°N 121.88°W
[1]
Type
Oblique-slip reverse
Areas affected
Central Coast (California)
San Francisco Bay Area
United States
Total damage
$5.6–6 billion[1][5] (equivalent to $11.6–12.4 billion today)
Max. intensity
IX (Violent)[1]
Peak acceleration
0.65g (at epicenter)[2]
Tsunami
Yes[6][7]
Landslides
1,000–4,000[1][2]
Foreshocks
5.3 ML June 27, 1988[8]
5.4 ML August 8, 1989[8]
Casualties
63 killed, 3,757 injured[1][9]
The 1989 Loma Prieta earthquake occurred on California’s Central Coast on October 17 at 5:04 p.m. local time (1989-10-18 00:04 UTC). The shock was centered in The Forest of Nisene Marks State Park 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.
Because it happened during a national live broadcast of the 1989 World Series, taking place between Bay Area teams San Francisco Giants and the Oakland Athletics, it is sometimes referred to as the "World Series earthquake". Rush-hour traffic on the Bay Area freeways was 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 man-made structures and other related accidents contributed to casualties occurring in San Francisco, Los Altos, and Santa Cruz.
Contents
1
Background
1.1
Forecasts
1.2
Foreshocks
2
Earthquake
2.1
Characteristics
2.2
Ground effects
2.3
Injuries and fatalities
2.4
Magnetic disturbances
3
Damage
3.1
Marina District
3.2
Santa Cruz and Monterey counties
3.3
San Francisco–Oakland Bay Bridge
3.4
Oakland and Interstate 880/Cypress Viaduct
3.5
Effects on transportation
4
1989 World Series
5
In popular culture
6
See also
7
References
8
External links
Background[edit]
See also: List of fault zones
The history of earthquake investigations in California has been largely focused on the San Andreas Fault System, due to its strong influence in the state as the boundary between the Pacific Plate and the North American Plate; it is the most studied fault on Earth. Andrew Lawson, a geologist from the University of California, Berkeley, had named the fault after the San Andreas Lake (prior to the occurrence of the 1906 San Francisco earthquake) and later led an investigation into that event. The San Andreas Fault ruptured for a length of 290 mi (470 km) during the 1906 shock, both to the north of San Francisco and to the south in the Santa Cruz Mountains region. Several long term forecasts for a large shock along the San Andreas Fault in that area had been made public prior to 1989 (the event and its aftershocks occurred within a recognized seismic gap) but the earthquake that transpired was not what had been anticipated. The 1989 Loma Prieta event originated on an undiscovered oblique-slip reverse fault that is located adjacent to the San Andreas Fault.[11]
Forecasts[edit]
Loma Prieta Peak in the Santa Cruz Mountains
See also: California earthquake forecast and Earthquake prediction
Since many forecasts had been presented for the region near Loma Prieta, seismologists were not taken by surprise by the October 1989 event. Between 1910 and 1989 there were 20 widely varying forecasts that were announced, with some that were highly specific, covering multiple aspects of an event, while others were less complete and vague. With a M6.5 event on the San Juan Bautista segment, or an M7 event on the San Francisco Peninsula segment, United States Geological Survey (USGS) seismologist Allan Lindh's 1983 forecasted rupture length of 25 miles (40 km) (starting near Pajaro Gap, and continuing to the northwest) for the San Juan Bautista segment nearly matched the actual rupture length of the 1989 event. An updated forecast was presented in 1988, at which time Lindh took the opportunity to assign a new name to the San Juan Bautista segment – the Loma Prieta segment.[12]
In early 1988, the Working Group for California Earthquake Probabilities (WGCEP) made several statements regarding their forecasts for the 225 mi (360 km) northern San Andreas Fault segment, the 56 mi (90 km) San Francisco Peninsula segment, and a 18.8–22 mi (30–35 km) portion of that segment which was referred to as the southern Santa Cruz Mountains segment. The thirty year probability for one or more M7 earthquakes in the study area was given as 50%, but because of a lack of information and low confidence, a 30% probability was assigned to the Southern Santa Cruz Mountains segment. Two moderate shocks, referred to as the Lake Elsman earthquakes by the USGS, occurred in the Santa Cruz Mountains region in June 1988 and again in August 1989. Following each event, the State office of Emergency Services issued (for the first time in Bay Area history) short term advisories for a possible large earthquake, which meant there was "a slightly increased likelihood of an M6.5 event on the Santa Cruz Mountains segment of the San Andreas fault". The advisories following the two Lake Elsman events were issued in part because of the statements made by WGCEP and because they were two of the three largest shocks to occur along the 1906 earthquake's rupture zone since 1914.[8][12]
Foreshocks[edit]
See also: Coulomb stress transfer and Foreshock
USGS ShakeMaps showing similar intensity patterns for the June 1988 (left) and August 1989 events near Lake Elsman in the Santa Cruz Mountains
The ML 5.3 June 1988 and the ML 5.4 August 1989 events also occurred on previously unknown oblique reverse faults and were within 3 mi (4.8 km) of the M6.9 Loma Prieta mainshock epicenter, near the intersection of the San Andreas and Sargent faults. Total displacement for these shocks was relatively small (approximately 4 in (100 mm) of strike-slip and substantially less reverse-slip) and although they occurred on separate faults and well before the mainshock, a group of seismologists considered these to be foreshocks due to their location in space and time relative to the main event. Each event's aftershock sequence and effect on stress drop was closely examined, and their study indicated that the shocks affected the mainshock's rupture process. Following the August 8, 1989, shock, in anticipation of an upcoming large earthquake, staff at the University of California, Santa Cruz deployed four accelerometers in the area, which were positioned at the UCSC campus, two residences in Santa Cruz, and a home in Los Gatos. Unlike other nearby (high gain) seismographs that were overwhelmed (driven off scale) by the large magnitude mainshock, the four accelerometers captured a useful record of the main event and more than half an hour of the early aftershock activity.[8][13]
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