Earthquake terminology

A Quick Lesson in Earthquake Terminology

When you start thinking about earthquakes, it’s easy to feel overwhelmed and frightened. But at Quake Kit, we want you to understand that getting prepared takes away a huge percentage of the fear and stress. Instead of being afraid, get prepared! And once you’ve got your survival kit ready, your household plan in place and your earthquake knowledge ingrained, you can let your instincts take over to greatly increase your chances of earthquake survival!

To that end, we want to share some terminology with you so you can begin to steep yourself in earthquake knowledge immediately!

Body wave: a seismic wave that moves through the interior of the earth. P and S waves are body waves. Each type of wave shakes the ground in different ways.

Displacement: the amount any reference point affected by an earthquake has moved from where it was before the earthquake.

Earthquake: a term used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip, or by volcanic or magmatic activity, or other sudden stress changes in the earth.

Earthquake Foreshock: an earthquake that occurs before a larger seismic event (the mainshock) and is related to it in both time and space. The designation of an earthquake as foreshock, mainshock or aftershock is only possible after the full sequence of events has happened.

Earthquake Mainshock: the largest earthquake in a sequence, sometimes preceded by one or more foreshocks, and almost always followed by many aftershocks.

Earthquake Aftershock: aftershocks– that take the form of a cloud of tremors that encompasses the initial rupture. In other words, aftershocks are mainly caused by the stress added to the crust by the initial earthquake. Although always smaller than the Mainshock, Aftershocks can still cause damage and are not to be taken lightly.

Epicentre: (aka epicentrum) the point on the Earth’s surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates.

Hypocentre: the hypocenter is the point within the earth where an earthquake rupture starts. The epicenter is the point directly above it at the surface of the Earth. Also commonly termed the focus.

Paleoseismicity: refers to earthquakes recorded geologically, most of them unknown from human descriptions or seismograms. Geologic records of past earthquakes can include faulted layers of sediment and rock, injections of liquefied sand, landslides, abruptly raised or lowered shorelines, and tsunami deposits.

Richter Scale: a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.

To take your knowledge further, check out this full glossary of earthquake terms and try making yourself some flashcards and turning a quiet evening around the house into a trivia night! You could even add prizes!

-Content created by Sophie Wooding – Writer, gardener, cyclist and emergency preparedness enthusiast!

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