Page 82 - Laboratory Manual in Physical Geology

2. An average displacement of about 5 m (16 ft) along the San Andreas Fault was associated with the devastating 1906 San

Francisco earthquake that killed people and destroyed properties. Assuming that all displacement along the fault was
produced by Earth motions of this magnitude, how often must such earthquakes have occurred in order to account for the
total displacement? Show your work.

NEVADA
CALIFORNIA

North

GPS station
0 50
Millimeters/year
Inches/year
0 1 2

San Andreas Fault
MEXICO
0 100
Kilometers

B. The above map shows some Global Positioning System (GPS) reference stations and observations from the JPL-NASA GPS

Time Series website at http://sideshow.jpl.nasa.gov/post/series.html . Length of the arrows indicates absolute plate motion ,
the direction and rate that the plate is moving in mm/yr at the GPS station (which is attached to bedrock of the plate).

1. Notice that both plates are moving northwest here. Estimate in cm/year
how much faster the Pacific Plate is moving than the North American Plate. ____________________ cm/yr
2. Add half arrows along the San Andreas Fault to show the relative movement between the two plates.

C. REFLECT & DISCUSS What is the difference between absolute plate motion and relative plate motion?

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