Earthquakes Flashcards
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is re-designated as the main shock and the original main shock is re-designated as a foreshock.
Aseismic
Not characterized by earthquake activity. It is used to describe a region free of earthquakes or in terms of buildings, it describes those designed to withstand earthquakes.
Benioff/Wadati-Benioff zone
A dipping planar (flat) zone of increased earthquake activity that is produced by the interaction of a downgoing oceanic crustal plate with an overriding continental or oceanic plate. These earthquakes can be produced by slip along the subduction thrust fault or by slip on faults within the downgoing plate as a result of bending and extension as the plate is pulled into the mantle. The zones have dips typically ranging from 40 to 60 degrees.
Magnitude
size/extent, e.g. the size/magnitude of an earthquake on the Richter scale, the size of volcanic eruption on the VEI, the extent of damages/consequences of a tectonic activity
Liquefaction
a phenomenon whereby a saturated or partially saturated soil substantially loses stength and stiffness in response to an applied stress (Earthquake shaking) or other sudden change s in stress condiiton causing it to behave like a liquid
Epicentre
The point on the Earth’s surface vertically above the focus of an earthquake
Focal depth
The depth below the Earth’s surface of the hypocentre of an earthquake. In seismology, the depth of focus or focal depth refers to the depth at which an earthquake occurs.
Focus/hypocentre
the point within the earth where an earthquake originates The location where the earthquake begins. The ground ruptures at this spot, then seismic waves radiate outward in all directions.
