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Depth of focus (tectonics) In seismology, the depth of focus or focal depth is the depth at which an earthquake occurs. Earthquakes occurring at a depth of less than 70 km (43 mi) are classified as shallow-focus earthquakes, while those with a focal depth between 70 km (43 mi) and 300 km (190 mi) are commonly termed mid-focus or intermediate ...
In seismology, an isoseismal map is used to show lines of equally felt seismic intensity, generally measured on the Modified Mercalli scale. Such maps help to identify earthquake epicenters, particularly where no instrumental records exist, such as for historical earthquakes. They also contain important information on ground conditions at ...
Hypocenter. A hypocenter or hypocentre (from Ancient Greek ὑπόκεντρον (hupókentron) 'below the center'), also called ground zero[1][2] or surface zero, is the point on the Earth 's surface directly below a nuclear explosion, meteor air burst, or other mid-air explosion. In seismology, the hypocenter of an earthquake is its point of ...
For the seismology term, see Depth of focus (tectonics). Depth of focus is a lens optics concept that measures the tolerance of placement of the image plane (the film plane in a camera) in relation to the lens. In a camera, depth of focus indicates the tolerance of the film's displacement within the camera and is therefore sometimes referred to ...
Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic ...
Focal mechanism. The focal mechanism of an earthquake describes the deformation in the source region that generates the seismic waves. In the case of a fault -related event, it refers to the orientation of the fault plane that slipped, and the slip vector and is also known as a fault-plane solution. Focal mechanisms are derived from a solution ...
t. e. The epicenter (/ ˈɛpɪˌsɛntər /), epicentre, or epicentrum[1] in seismology is the point on the Earth 's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates.
Even if the depth of focus of an earthquake is very deep, it can still have a very short epicentral distance. [3] When measuring the epicentral distance of an earthquake with a small epicentral distance, first measure the reading of the initial motion of P wave, and then confirm the arrival of S wave.