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During an earthquake, seismic waves propagates in all directions from the hypocenter. Seismic shadowing occurs on the opposite side of the Earth from the earthquake epicenter because the planet's liquid outer core refracts the longitudinal or compressional while it absorbs the transverse or shear waves . Outside the seismic shadow zone, both ...
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. [Notes 3] The value of the epicenter distance Δ is found on the travel timetable according to the arrival time difference between the P wave and S wave. [4]
A major earthquake measuring 7.4 hit Taiwan early Wednesday, killing 9 and injuring at least 1,000. A 7.4 earthquake is exponentially more destructive than the 4.8 quake that struck central New ...
Isoseismal map for the 1968 Illinois earthquake. In seismology, an isoseismal map is used to show countour 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.
The earthquake will be strongest at its epicenter, the point on the surface directly above where the quake started, and the effects will be diminished as they spread further.
“Drop, Cover, Hold on. Protect yourself,” the U.S. Geological Survey warned moment before the eathquake struck.
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.
With an isoseismal map of the observed intensities (see illustration) an earthquake's magnitude can be estimated from both the maximum intensity observed (usually but not always near the epicenter), and from the extent of the area where the earthquake was felt.