Jeffrey Marshall, Dan Orange, and Alfred Hochstaedter; html by Joe Overton
Earthquakes occur along plate boundaries, like the one shown at
right between the Pacific Plate (to the west) and the
North American Plate (to the east). The yellow dots represent
earthquake epicenters, which are aligned along faults. As the
plates move, stress builds up along faults. When this stress
is released, the blocks or plates move and an earthquake occurs.
The distribution of epicenters reveals that several
fault zones -- on either side of San Francisco Bay and Santa Clara Valley
-- take up portions of the movement between the Pacific and North American
Plates. One of these faults, the San Andreas, runs through San
Juan Bautista, the
Santa Cruz mountains, north through the San Francisco Peninsula, off
shore from the Golden Gate, and then on-shore just east of the Pt.
Reyes Peninsula. The San Andreas Fault is considered the main boundary
between the Pacific and North American Plates.
At five in the afternoon on October 17, 1989 the San Andreas fault system
in northern California
had its first major quake since 1906. The quake was responsible for 62
deaths, 3,757 injuries, and over $6 billion in damage. Over 18,000 homes
and 2,600 businesses were damaged and about 3,000 people were left
homeless. This self-guided field trip takes you on a tour of the
Santa Cruz region after the 1989 Loma Prieta Earthquake. Select a topic
which interests you below by clicking on the highlighted key word.
1. Tectonics: This page
investigates why and how the earthquake occured.
Damage Pages.
The following
pages are organized by subject, and investigate the root causes of
damage caused by the quake:
2.Damged Buildings: Examines why buildings
failed during the quake.
3.Liquefaction: A condition where soil flows
like a liquid. This caused extensive damage in the area including the
collapsed overpasses and freeways.
4.Cracks: Extensional features caused by
earthquake uplift.
5.Landslides: Some up to hundreds of meters
long destroyed houses and blocked roads and freeways.
6.Technical Data: Take a look at
the seismogram and other interesting data.
This gets you to the next page.
This gets you back to this page.