Transcript The San Andreas Fault

The San Andreas Fault
By Kevin Buckley
And Nicholas Schuch, Esquire
Here are the earth’s plates
California’s Faults
• The Pacific Plate (on the west) is moving
Northwest, relative to the North American
Plate (on the east)
• The San Andreas Fault is the master fault
of an extremely complex fault system
• The SAF is more than 800 miles long, and
extends at least 10 miles into the earth
Your Fault, My Fault
• The fault varies in
width from a few
hundred feet to a mile
• The fault zone is
mostly consistent of
fault gouge
(pulverized rock) and
a few solid pieces of
rock
The earth is shaking
• The fault moves
about 2 inches
annually
– Fault is about 15-20
million years old
– Some blocks of crust
may have moved
through more than 20
degrees of latitude
– That is pretty far
How Dangerous?
The SAF has had three major earthquakes
1. 1857: 350 KM ruptured in Southern CA,
estimated magnitude was 7.9
2. 1906: 430 KM ruptured in Northern CA,
estimated magnitude was 7.8; Epicenter was
very close to San Francisco. 3000 deaths in
quake and subsequent fires
3. 1989: 40 KM ruptured near Santa Cruz;
estimated magnitude of 7.1, causing 63 deaths
Living with the Fault
• Because earthquakes are impossible to
prevent, humans near the fault have tried
to learn how to live with it
– Buildings in danger zones have been rebuilt
or strengthened
– Selective use of land: careful zoning
– Sustained efforts in learning how to predict
earthquakes
And that’s all
• Information taken from
http://pubs.usgs.gov and
http://www.worldhistory.com
5 questions
1. What is a geologic fault?
2. What is the San Andreas Fault, and what
is its special significance?
3. What are some of the specifications of
the fault?
4. How far has the fault moved (both
recently and geologically?
5. How destructive can the SAF be?