Not only was the data conclusive to this, but it revealed more seismic activity than previously hypothesized. An earthquake is a sudden, often violent movement of the earth s surface as a result of the release of energy from the earth s crust. The cause of this is that the earth is always bending slightly from tectonic forces. When this stressor pressure exceeds the strength of the rocks, the crust breaks and can snap into a new position. Vibrations from this are called seismic waves, which travel through and along the earth s surface.
Earthquakes often occur at faults.
A fault is where two large blocks of crustal rock have slipped or moved against each other. They can move up and down or horizontally to the left and right. Essentially, faults are weaknesses in the crust. This number includes quakes too small to be felt but large enough to be recorded as an earthquake. Ninety-five percent of them are along tectonic or crustal plate boundaries.