Seismic activity is defined as the types, frequency and size of earthquakes that happen over a period of time in a certain area. Many erupts are preceded by increased levels of seismic activity. The earthquakes are caused by fracturing and brittle failure of the subsurface rocks as new magma pushes it’s way up towards the surface. An example of seismic activity is how often earthquakes occur in the San Francisco Bay Area.
Lecture on Seismic Activity
