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{{defn|Instrument that includes the seismometer plus the system to record and display that motion, traditionally on paper or now digitally.}} |
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Revision as of 11:47, 23 November 2025
- Earthquake
- The shaking of the Earth’s surface resulting from a sudden release of energy in the lithosphere that creates seismic waves.
- Lithosphere
- The rigid, outermost rocky shell of a terrestrial planet or natural satellite.
- Seismic wave
- A mechanical wave of acoustic energy that travels through the Earth or another planetary body. It can result from an earthquake (or generally, a quake), volcanic eruption, magma movement, a large landslide and a large man-made explosion that produces low-frequency acoustic energy.
- Seismic intensity scale
- A scale that categorizes the intensity or severity of ground shaking (quaking) at a given location, such as resulting from an earthquake.
- Seismic magnitude scale
- A scale which is used to describe the overall strength or “size” of an earthquake. Magnitudes are usually determined from measurements of an earthquake’s seismic waves as recorded on a seismogram.
- Seismicity
- A measure encompassing earthquake occurrences, mechanisms, and magnitude at a given geographical location. As such, it summarizes a region’s seismic activity.
- Hypocenter
- The point of origin of an earthquake below ground.
- Epicenter
- The point on the Earth’s surface directly above a hypocenter or focus.
- Fault
- A planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements.
- Volcanism
- Volcanism, is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon.
- Soil liquefaction
- A phenomenon when a cohesionless saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake.
- Tectonics
- Processes that result in the structure and properties of Earth’s crust and its evolution through time.
- Strike-slip fault
- A fault where the fault surface (plane) is usually near vertical, and the footwall moves laterally either left or right with very little vertical motion.
- Earth’s crust
- The thick outer shell of rock comprising less than one percent of the Earth’s radius and volume. It is the top component of the lithosphere.
- Elastic-rebound theory
- Theory that explains that an earthquake occurs when stress on rocks along a fault exceeds their strength, causing them to deform elastically and store energy. When the stress becomes too great, the rocks suddenly snap back to their original shape, or “rebound,” releasing the stored energy in the form of seismic waves that cause earthquakes.
- Seismic retrofitting
- The modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes.
- Seismic engineering
- Interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, in order to make such structures more resistant to earthquakes so that they will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake.
- Episodic tremor and slip
- A seismological phenomenon observed in some subduction zones that is characterized by non-earthquake seismic rumbling, or tremor, and slow slip along the plate interface.
- Aseismic creep
- Measurable surface displacement along a fault in the absence of notable earthquakes, which may also occur as “after-slip” days to years after an earthquake.
- Asperity
- Area on an active fault where there is increased friction, such that the fault may become locked, rather than continuously slipping as in aseismic creep. Earthquake rupture generally begins with the failure of an asperity, allowing the fault to move.
- Elastic energy
- The mechanical potential energy stored in the configuration of a material or physical system as it is subjected to elastic deformation by work performed upon it. Elastic energy occurs when objects are impermanently compressed, stretched or generally deformed in any manner.
- Interplate earthquake
- Earthquake that occurs at the boundary between two tectonic plates, accounting for more than 90 percent of the total seismic energy released around the world.
- Fracture
- Any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces.
- Subduction
- Geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth’s mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plate, the heavier plate dives beneath the other and sinks into the mantle.
- Volcano tectonic earthquake
- Earthquake is caused by the movement of magma beneath the surface of the Earth. The movement results in pressure changes where the rock around the magma has a change in stress. At some point, this stress can cause the rock to break or move.
- Earthquake swarm
- Sequence of seismic events occurring in a local area within a relatively short period.
- Aftershock
- A smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock.
- Doublet earthquake
- Multiple earthquakes with nearly identical waveforms originating from the same location.
- Seismometer
- An instrument that responds to ground displacement and shaking such as caused by quakes, volcanic eruptions, and explosions.
- Seismograph
- Instrument that includes the seismometer plus the system to record and display that motion, traditionally on paper or now digitally.
- Seismogram
- The graphic output of a seismograph recorded on paper or film, now recorded and processed digitally.
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