Faults and Earthquakes
What causes earthquakes?
- Large scale tectonic movements of the Earth's plates cause pressures to build up in the crust.
- Deep below the surface, pressures and temperatures are high.
- There rocks actually "flow" and "fold" without rupturing (breaking).
- Closer to the earth's surface rocks are more rigid.
- Pressures are released along a fault where rocks break and snap to a new position.
- This movement is an earthquake.
- Most of the stored energy is released in the first movement along the fault.
- Smaller amounts of energy are released in aftershocks.
- Aftershocks are less severe than the initial earthquakes and may occur over many months.
Types of faults
- The fault is a break in the Earth's surface along which movement occurs.
- We experience such movement as an earthquake.
- Forces of compression, tension and shear in the earth's crust result in three main types of breaks near the surface.
- A normal fault results when tension pulls on the fault.
- A reverse fault results when the fault is compressed.
- Strike-slip faults result from shearing forces.