The 1989 Loma Prieta Earthquake and Its Reach Into the Bay Area

The Loma Prieta earthquake struck California on October 17, 1989, at 5:04 p.m. Pacific time. Its epicenter was in The Forest of Nisene Marks State Park in Santa Cruz County, about 10 miles northeast of Santa Cruz. The earthquake took its name from nearby Loma Prieta Peak in the Santa Cruz Mountains.

Measured at magnitude 6.9, the earthquake reached a maximum Modified Mercalli intensity of IX, classified as violent. It caused 63 deaths and 3,757 injuries. Damage was especially severe in Santa Cruz County. Monterey County, south of the epicenter, experienced less damage, while the earthquake’s effects extended north into the San Francisco Bay Area.

For San Francisco readers, the event’s geographic reach is central to understanding its local significance. The earthquake affected the San Francisco Peninsula and crossed the bay to Oakland. The source account identifies those areas as part of the broader zone affected by the shock, though the supplied material does not provide a detailed breakdown of damage in San Francisco itself.

The earthquake occurred on a section of the San Andreas Fault System beneath the Santa Cruz Mountains. That segment had been relatively inactive since the 1906 San Francisco earthquake and had been identified as a seismic gap. Two moderate foreshocks preceded the main event: one in June 1988 and another in August 1989.

Although the earthquake occurred along the San Andreas Fault System, it did not produce surface faulting. Other forms of ground failure were widespread, including landslides, particularly around the Summit area of the Santa Cruz Mountains. Liquefaction was also a significant problem, according to the source material.

The event therefore connected several distinct landscapes and communities: the mountainous area around the epicenter, Santa Cruz County, the Peninsula and the urban areas around San Francisco Bay. Its casualty count, intensity and broad regional effects distinguish it from a localized shock. For an LGBTQ-focused local newsroom, the supplied information supports a historical and civic explainer about an earthquake that affected the wider Bay Area, but it does not document impacts on LGBTQ people, organizations or services. This backgrounder accordingly stays with the documented seismic history and the earthquake’s connection to the San Francisco region.

Source and reuse information This automatically generated backgrounder adapts text from “1989 Loma Prieta earthquake” on Wikipedia: https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake The adapted text is released under the Creative Commons Attribution-ShareAlike 4.0 International license (CC BY-SA 4.0): https://creativecommons.org/licenses/by-sa/4.0/. The source article’s linked references are provided below where available. This story has not been independently reviewed or fact-checked.

Further links listed by the Wikipedia page (not independently checked): - https://books.google.com/books?id=bTkrAAAAYAAJ - https://books.google.com/books?id=rh0yk2j_gyAC&pg=SL1-PA43 - https://web.archive.org/web/20131211053714/http://www.ktvu.com/news/news/bay-area-television-news-prepares-for-end-of-an-er/nKdtb/ - https://www.youtube.com/watch?v=A85YVEG_-v4 - https://web.archive.org/web/20121105135903/http://www.sfmuseum.net/alm/quakes4.html - https://web.archive.org/web/20160304002551/http://www.sfmuseum.net/alm/quakes3.html Image rights Photograph description: Damage in San Francisco's Marina District the day after the October 1989 Loma Prieta earthquake struck. October 1989 photo by Nancy Wong Creator: Nancy Wong. License: CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0). Original image page: https://commons.wikimedia.org/wiki/File%3ADamage_in_San_Francisco's_Marina_District_the_day_after_the_October_1989_Loma_Prieta_earthquake_struck.jpg. The image was resized for display; no other changes were made.