Calculating the rate of movement along the San Andreas:

1. Wallace Creek has been offset by 430 feet to the right along the fault. The age of the stream deposits indicates that this offset began 3700 years ago. Based on these figures, calculate the average rate of movement along this segment of the fault in inches per year. Keep in mind that your estimate is the long term average, not the expected movement for each year.

a. Total offset in centimeters (or inches): centimeters (or inches)
b. Average offset per year: centimeters per year (or in./yr)

2. The great Fort Tejon earthquake of January 9, 1857 (7.8 magnitude) was the last major earthquake in this region. It ruptured a 220 mile segment of the San Andreas Fault and produced 33 feet of offset in this area. Based on the average rate of fault movement calculated in question 1, estimate how many years of accumulated strain were released during that earthquake. (This is a very simplistic general assumption, by the way, it is much more complicated than this!)

years of accumulated strain

3. Assuming that this segment of the San Andreas Fault ruptures at fairly regular intervals, and paleoseismic studies suggest that this may be true, estimate the year when the next great earthquake might occur along this section of the fault. (Again, this is a simplistic assumption.)

Approximate year of next great earthquake: