Types Of Earthquakes. CVO Website - Earthquakes and Seismicity. USGS/Cascades Volcano Observatory, Vancouver, Washington Seismic Swarms Volcanic (Long-Period) vs. Tectonic (Short-Period) Deep - Shallow - Surface Events - Harmonic Tremor Harmonic Tremor Seismic Waves and Signals Magnitude and Intensity Magnitude - Richter Scale Intensity - Modified Mercalli Scale From: USGS Earthquake Hazards Program, National Earthquake Information Center Website, 2002 A seismic swarm is by definition a localized surge of earthquakes, with no one shock being conspicuously larger than all other shocks of the swarm. Seismic swarms typically last longer than more typical earthquake sequences that consist of a main shock followed by significantly smaller aftershocks. Seismic swarms occur in a variety of geologic environments. They are not known to be indicative of any change in the long-term seismic risk of the region in which they occur. From: Tilling, et.al., 1987, Eruptions of Hawaiian Volcanoes: Past, Present, and Future: USGS General Interest Publication I.
II. Long-Period Earthquake - John Seach. Lexique volcanologique. Geologylink® - Glossary. Grand dictionnaire terminologique.