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Thurston's earthquake theorem states that for any two points x, y of a Teichmüller space there is a unique left earthquake from x to y.It was proved by William Thurston in a course in Princeton in 1976–1977, but at the time he did not publish it, and the first published statement and proof was given by Kerckhoff (1983), who used it to solve the Nielsen realization problem.
Time marks show when the earthquake occurred. Time is shown by half-hour (thirty-minute) units. Each rotation of the seismograph drum is thirty minutes. Therefore, on seismograms, each line measures thirty minutes. This is a more efficient way to read a seismogram. Secondly, there are the minute-marks.
The path that a wave takes between the focus and the observation point is often drawn as a ray diagram. Each path is denoted by a set of letters that describe the trajectory and phase through the Earth. In general, an upper case denotes a transmitted wave and a lower case denotes a reflected wave. The two exceptions to this seem to be "g" and "n".
The first scale for measuring earthquake magnitudes, developed in 1935 by Charles F. Richter and popularly known as the "Richter" scale, is actually the Local magnitude scale, label ML or M L. [11] Richter established two features now common to all magnitude scales.
English: Diagram of the epicenter of an earthquake in relation to its hypocenter/focus point. Derived from original work by Sam Hocevar. Derived from original work by Sam Hocevar. Русский: Эпицентр и гипоцентр землетрясения
In its most general sense, the word earthquake is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear tests. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the epicenter.
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Travel time in seismology means time for the seismic waves to travel from the focus of an earthquake through the crust to a certain seismograph station. [1] Travel-time curve is a graph showing the relationship between the distance from the epicenter to the observation point and the travel time.