Seismic activity is described by geologists as an elastic wave traveling through the Earth following an earthquake or other geological disturbance. Seismic activity encompasses the frequency, size and type of earthquake, according to the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, which monitors seismic activity throughout the world.
Seismic activity results not only from earthquakes, but from volcanoes and human activity, such as explosions. Seismologists use the Richter scale to measure the magnitude of earthquakes, volcanoes and other seismic activity throughout the world. Seismometers detect the presence of seismic activity. The CTBTO Preparatory Commission reports that sensitive seismometers are capable of picking up activity from a person stomping.
SMS Tsunami Warning indicates there are two primary types of seismic activity, both of which start at an earthquake's epicenter and travel outward in a manner resembling ripples in a pond. The first are body waves, which travel through the Earth's interior. The second type, surface waves, travel along the surface of the planet. Surface waves, which arrive after body waves, cause the greatest destruction to buildings, roads, bridges and other structures. As a rule, surface waves are not generated by deep earthquakes. They are, however, fast and are capable of traveling through granite at up to 2 miles per second.