October 18: On This Day in World History … briefly
Since many forecasts had been presented for the region near Loma Prieta, seismologists were not taken by surprise by the October 1989 event.
1989: Bay evaluates devastation after quake rocks Cisco
The 1989 Loma Prieta earthquake occurred on California’s Central Coast on October 17 and the extent of the damage was really only evident on October 18. The shock was centered in The Forest of Nisene Marks State Park approximately 10 miles (16km) 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 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 a large number of 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, 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.
Most notable historic snippets or facts extracted from the book ‘On This Day’ first published in 1992 by Octopus Publishing Group Ltd, London, as well as additional supplementary information extracted from Wikipedia.
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