The Ms 7.1 mainshock of the Loma Prieta earthquake sequence occurred at 5:04:15 p.m. Pacific Daylight Time on 17 October 1989, approximately 50 miles south of San Francisco on the San Andreas fault in the southern Santa Cruz Mountains near the summit of the Loma Prieta Mountain. This earthquake killed 62 people, injured 3,757, destroyed 367 businesses, and left 12,000 homeless.
The most dramatic damage in San Francisco, and perhaps throughout the region affected by the Loma Prieta earthquake, occurred in the Marina District. The Marina district was created with man-made fill primarily by hydraulic deposition of poorly graded sands. Liquefaction and ground failure occurred throughout the Marina, but primarily in a zone of failure just bayward of the original shoreline, resulting in broken water and gas piping and amplification of ground motion estimated to be a factor of four over nearby rock sites. A building-by building survey of damage indicated overall building damage in the Marina district to be about 3%, while average damage to four story, wood-frame corner apartment buildings is estimated at nearly 20%. Building damage was observed to be most severe near the western edge of the fill, where a large fire broke out in a collapsed building, resulting in one death and the destruction of four buildings.
*These images and text descriptions are reproductions of slides purchased from the EERI (Earthquake Engineering Research Institute). For more information, please visit http://www.eeri.org.
