Thrust Faults
Kristin F.
A thrust fault is when one piece of land falls over, under, or beside another piece of land.
The Mount St. Helens Thrust Fault
From 1980 to 1982, parts of the crater floor (of Mount St. Helens) became slightly wrinkled several weeks before eruptions. A few wrinkles developed into thrust faults, a low-angle fracture, along which rocks above the fracture are pushed over rocks below the fractures. By summer 1981, a complex system of thrust blocks had disrupted much of the southwestern part of the crater floor. The thrust faults formed as rising magma forcefully ruptured the crater floor, shoving parts of it upward and outward from the vent toward the rigid crater walls. Before the August 18, 1982, eruption, the leading edge of one thrust fault grew from less than 30 centimeters to roughly 5 meters high a few days before the eruption
this information was found at http://vulcan.wr.usgs.gov/Glossary/CracksNThrusts/description_thrust_faults.html
California Faults
Though there's potential for catastrophe, the chances are slim. In the worst-case scenarios detailed in the study, the biggest quakes occur once every 2,100 years on one of the faults and another 8,800 years on the other. It's possible the faults release their energy in smaller but more frequent spurts, the researchers reported in the October edition of the journal Geology. "Because this is new and we can't access it easily, we don't have the knowledge base yet to decide whether it is going to rupture in small pieces or in one single event," said study author John Shaw of Harvard University. "The critical issue for hazard assessment is really just defining the size of these faults," he added, "The size obviously dictates the potential earthquake magnitude."
this information found at http://www.cbc.ca/cp/world/000930/w093059.html
these pictures were found at http://www.mc.maricopa.edu/academic/phy_sci/Geology/faults.html
