# 6.5: Activity 6D - Earthquakes and the Bay Area

The following exercises use Google Earth. Start by examining the USGS site for the 1906 earthquake that hit Northern California. There are several links available on this page. Spend some time familiarizing yourself with the site.

Scroll down to the section entitled “The Northern California Earthquake, April 18, 1906” and open the link. The San Andreas Fault, located here in California, is approximately 800 miles long. In 1906, a major earthquake occurred along a northern portion of the fault.

1. Scroll down and check out the Rupture Length and Slip. How long was the rupture length (the length of the fault that was affected)?

1. 25 miles

2. 74 miles

3. 198 miles

4. 296 miles

5. 408 miles

2. Horizontal slip, or relative movement along the fault, ranged from 2-32 feet. Check out all the measurements along the fault by clicking the Rupture Length and Slip, Google Earth file at the bottom of the section. Locate the epicenter of the 1906 quake (about 2 miles west of San Francisco). Does the amount of horizontal slip decrease faster along the northern end or the southern end of the rupture?

1. Northern end of the rupture

2. Southern end of the rupture

Go back to the “The Northern California Earthquake, April 18, 1906” page and scroll down to Shaking Intensity. Check out the intensity values by clicking the Shaking Intensity, Google Earth file at the bottom of the section. Note - if your map begins to get difficult to read, remember that by clicking on a checkbox in the Places folder, you can remove prior data. Use the search box to display the desired location.

1. What was the shaking intensity like in Sacramento?

1. Light

1. Strong

1. Severe

1. Violent

1. Extreme

1. What was the shaking intensity like in Sebastopol?

1. Light

2. Strong

3. Severe

4. Violent

5. Extreme

1. Navigate to the “Earthquake Hazards of the Bay Area Today”. Download the Earthquake Probabilities for the Bay Area, Google Earth file. Examine the map carefully. The USGS has calculated the probability of an M≥6.7 earthquake in the Bay Area between 2003-2031. In which part of the Bay Area is the probability highest?

1. Northwest Bay Area

2. Southeast Bay Area

1. Go back to the “Earthquake Hazards of the Bay Area Today” page and download the Liquefaction Susceptibility in San Francisco, Google Earth file. Observe the overall trend in areas affected by liquefaction. Based on this map, are areas more susceptible to liquefaction inland or along the coast?

1. Inland

2. Along the coast