An earthquake is the perceptible shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's crust that creates seismic waves.

Seismic waves are waves of energy that travel through the Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy.

Earth is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only astronomical object known to harbor life.

In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle.

Introduction to Earthquakes by Frank Gregorio


Earthquakes can be violent enough to toss people around and destroy whole cities.

Earthquakes 101 | National Geographic by National Geographic


The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.


Earthquakes are measured using observations from seismometers.

Seismometers are instruments that measure motion of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources.


The moment magnitude is the most common scale on which earthquakes larger than approximately 5 are reported for the entire globe.

The Richter magnitude scale assigns a magnitude number to quantify the energy released by an earthquake.


The more numerous earthquakes smaller than magnitude 5 reported by national seismological observatories are measured mostly on the local magnitude scale, also referred to as the Richter magnitude scale.


These two scales are numerically similar over their range of validity.


Magnitude 3 or lower earthquakes are mostly imperceptible or weak and magnitude 7 and over potentially cause serious damage over larger areas, depending on their depth.

A dam is a barrier that impounds water or underground streams.


The largest earthquakes in historic times have been of magnitude slightly over 9, although there is no limit to the possible magnitude.


Intensity of shaking is measured on the modified Mercalli scale.


The shallower an earthquake, the more damage to structures it causes, all else being equal.

Ceteris paribus or caeteris paribus is a Latin phrase meaning "other things equal".


At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground.


When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami.

The epicenter, epicentre or epicentrum is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates.

A tsunami, also known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake.


Earthquakes can also trigger landslides, and occasionally volcanic activity.

A landslide, also known as a landslip, is a form of mass wasting that includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows.


In its most general sense, the word earthquake is used to describe any seismic event — whether natural or caused by humans — that generates seismic waves.


Earthquakes are caused mostly by rupture of geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests.

In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock mass movement.

Underground nuclear testing is the test detonation of nuclear weapons that is performed underground.


An earthquake's point of initial rupture is called its focus or hypocenter.


The epicenter is the point at ground level directly above the hypocenter.

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