Chapter 19 Earth quakes. I. Forces within Earth. Stress and Strain 1. Most earthquakes occur when rocks fracture, or break, deep within Earth. 2. Fractures form when stress, forces per unit area acting on a material exceeds the strength of the rocks involved.
1. Most earthquakes occur when rocks fracture, or break, deep within Earth.
2. Fractures form when stress, forces per unit area acting on a material exceeds the strength of the rocks involved.
1. A fracture along which movement occurs is called a fault.
2. There are three basic types of faults, reverse, normal and strike-slip fault.
1. Primary waves or P-waves squeeze and pull rocks in the same direction along which the waves are traveling.
3. Surface waves are a third type of seismic wave that move in two directions as they pass through rock.
1. Seismometer is an instrument that detect and record vibrations.
2. Seismogram- the record produced by a seismometer.
1. The amount of energy released during and earthquake is measured by its magnitude.
2. An earthquake’s rating on the Richter scale is based on the size of the largest seismic waves generated by the quake.
4. Modified Mercalli scale rates the types of damage and other effects of an earthquake as noted by observes during and after its occurrence.
1. The exact location of an earthquake’s epicenter and the time of the quake’s occurrence are initially unknown.
1. Seismologists have collected and plotted the locations of numerous earthquake epicenters.
2. Almost 80% of all earthquakes occur in the Circum-Pacific Belt.
1. The damage produced by an earthquake is directly related to the strength or quality of the structures involved.
3. Wooden structures are strong.
5. In addition to their effects on structures made by humans, earthquakes can destroy Earth itself-landslides.
8. Seismic gaps are sections of active faults that haven’t experienced significant earthquakes for a long period of time.