San Andreas Fault

San Andreas Fault Presentation by: Zack Bick Erin Riggs Alicia Helton Cara Dickerson

What is it? • San Andreas Fault, geological fault zone in California • 800mi long and approx. 10mi deep • Right lateral strike-slip fault • Imperial Valley to Point Arena • Marks the boundary between N.American and Pacific plates • Movement of the plates cause earthquakes

Surface Features • A linear trough reveals the presence of the fault • The fault zone is marked by distinctive landforms • These include long straight escarpments, narrow ridges, and small un-drained ponds • Stream channels characteristically jog sharply to the right where they cross the fault

Brief History • The San Andreas Fault has been dated at 29 million years old • The greatest recorded movement at one time was 5 meters in the great San Francisco Earthquake of 1906 • This measured an 8.25 on the Richter Scale

Major Earthquakes Along the Fault • 1906, San Francisco • Began at 5:12 am, lasted 20-25 seconds and the aftershocks lasted 45-60 seconds • It measured 8.25 on the Richter Scale

1906 San Francisco Quake • The number of deaths resulting from the quake and the fire following the quake was 3,000 • The total number of injuries was 225,000 • The property damage that occurred was estimated at $400million in 1906 dollars.

1952 Kern County Quake • Occurred on July 21, at 5 am • The quake measured 7.5 on the Richter Scale • The quake was felt from Reno, Nevada to San Diego, California

1952 Quake • The quake came as a surprise to geologists • The quake was responsible for: • 12 deaths • 18 injuries • $50 million in property damage

1989 Loma Prieta Quake • Occurred October 17th, at 5 pm • The magnitude was estimated 7.1 on the Richter Scale • The quake did not come as a surprise to geologists

1989 Quake • The quake caused damage in San Francisco and Oakland • The 1989 earthquake caused: • $7 billion in damage • 12,000 displaced people • 3,757 injuries and 67 deaths

New Designs and Construction of Buildings in Earthquake Prone Areas • Buildings, homes, bridges and overpasses will be built to withstand strong shaking • Some cities have programs to tear down unstable buildings or homes • Automatic shut off of gas lines when the P-wave hits to limit fire hazards

Selective Use of Land • Places not to build homes or buildings: • Ground failure areas of liquefaction • Landslide prone areas

Accurate Prediction of Earthquakes(A Work In Progress) • China has been the only country who has predicted an earthquake nine hours before, in which they saved lives • However, the next quake they had came unexpected • In Tokyo, Japan they are hard away at work trying to learn how to successfully predict earthquakes • Other geologists around the world are also working to find an answer to predict the quakes

Earthquake Probability • Research conducted since the 1989 quake helped USGS and other scientists conclude: • 70% probability of at least one magnitude 6.7 or greater quake • 21% probability of that 70% is on the San Andreas Fault • The quake might strike the San Francisco Bay region before 2030 • Major quakes may occur in any part of this region • Communities in the Bay Area region continue to prepare for earthquakes

Earthquake Odds • Rates of large earthquakes in the San Francisco have dropped after the Great 1906 Earthquake. • San Andreas Fault slipped so much over such a great length in that quake that the strain was reduced on most faults throughout the region. • Strain has been slowly building up again. • However, level of seismic activity has not yet reached that of the late 1800's.

In Conclusion, we’ve learned: • The geography of the San Andreas Fault • A few of the major quakes on the fault • What everyone can do to help reduce the risk of disaster when a quake hits • Probability of the next big earthquake

San Andreas Fault