Volcanic Earthquake
Definition
An earthquake associated with volcanic activity, caused by magma movement, gas pressure, or rock fracturing near a volcano. Often occurs in swarms and can signal an impending eruption.
Example
Thousands of small earthquakes preceded the 1980 eruption of Mount St. Helens.
Related Terms
Related Guides
What Is an Earthquake? A Complete Introduction
Learn what causes earthquakes, how they occur along fault lines, and why some regions experience more seismic activity than others.
Earthquake Swarms: When Small Quakes Won't Stop
Earthquake swarms produce hundreds of small tremors without a clear mainshock. Learn what causes them and whether they signal bigger events.
Moon Phases and Earthquakes: Is There a Connection?
Tidal forces from the moon have a tiny effect on earthquake triggering. Learn what research shows about lunar influence on seismicity.
Indonesia's Ring of Fire Position: Islands of Earthquakes
Indonesia spans multiple subduction zones on the Ring of Fire. Learn about its earthquake and tsunami risks across 17,000 islands.
Central America's Volcanic Earthquake Zone
Central America sits above the Cocos Plate subduction zone, producing earthquakes and volcanoes from Guatemala to Panama.
Caribbean Earthquake Risk: Hidden Hazards
The Caribbean faces earthquake and tsunami risk from multiple plate boundaries. Learn about the hidden seismic hazards threatening island nations.
Subduction Zones: Earth's Most Powerful Earthquake Factories
Subduction zones produce the world's largest earthquakes including the M9.5 Chile 1960 event. Learn how they work and where they exist.
The Ring of Fire: Why the Pacific Rim Shakes
90% of earthquakes occur around the Ring of Fire. Explore this 40,000 km horseshoe of volcanic and seismic activity.
Mantle Convection: The Heat Engine Driving Plate Motion
Earth's mantle circulates like a slow-motion boiler, driving tectonic plates. Learn how heat from the core powers earthquakes.
Frequently Asked Questions
The epicenter is the point on the Earth's surface directly above the hypocenter (focus) where the earthquake rupture begins. It is typically reported as latitude and longitude coordinates. The strongest shaking usually occurs near the epicenter, though local soil conditions and fault geometry can shift the zone of maximum damage.
A seismograph (or seismometer) is an instrument that detects and records ground motion caused by seismic waves. Modern broadband seismometers can detect movements smaller than the width of an atom. Networks of seismographs around the world enable scientists to locate earthquakes and determine their magnitude within minutes.
P-waves (primary waves) are compressional waves that travel fastest through rock, arriving first at seismic stations. S-waves (secondary waves) are shear waves that arrive later but cause more ground shaking. P-waves travel through solids, liquids, and gases; S-waves only travel through solids. The time difference between them helps determine earthquake distance.
The hypocenter (or focus) is the point within the Earth where an earthquake rupture initiates. It is described by latitude, longitude, and depth. The vertical distance between the hypocenter and the surface directly above is the earthquake's depth, which strongly influences how the earthquake is felt at the surface.
Seismology is the scientific study of earthquakes and the propagation of seismic waves through the Earth. It encompasses earthquake detection, location, and characterization; Earth's internal structure; seismic hazard assessment; and earthquake engineering. Seismologists use data from global seismograph networks to study these phenomena.