Toggle text. Effects of an earthquake Living with earthquakes Measuring earthquakes Shock waves Tsunami What causes an earthquake? What is an earthquake? Where do earthquakes happen? The P wave, or compressional wave, ultimately compresses and expands material in the same direction it is travelling. The next to arrive is the S wave which causes particles to oscillate. S waves can travel through solid material but not through liquid or gas.
Surface waves, in contrast to body waves can only move along the surface. They arrive after the main P and S waves and are confined to the outer layers of the Earth. They cause the most surface destruction. Earthquake surface waves are divided into two different categories: Love and Rayleigh. Love waves have a particle motion, which, like the S-wave, is transverse to the direction of propagation but with no vertical motion.
Their side-to-side motion like a snake wriggling causes the ground to twist from side to side, that's why Love waves cause the most damage to structures. The different S waves arrive after the P waves. One can imagine two types of shock waves: positive compression shocks which propagate into the direction where the density of the gas is a minimum, and negative rarefaction waves which propagate into the direction of maximum density.
The rupture speed of most earthquakes tops out around 5, to 6, mph 9, to 10, kilometers per hour which is slower than the speed at which seismic shear waves one type of seismic wave generated by an earthquake emanate from the epicenter of the quake.
After the stone hits the water ripples move outwards from the centre in every direction. These are often the most destructive waves in an earthquake. Shock waves radiate out from the point inside Earth where the earthquake begins.
This point is called the focus. Seismic waves are vibrations i. The most commonly used adaptation covers the range of intensity from the condition of "I -- Not felt except by a very few under especially favorable conditions," to "XII -- Damage total. Lines of sight and level are distorted. Objects thrown upward into the air. The maximum intensity experienced in the Alaska earthquake of was X; damage from the San Francisco and New Madrid earthquakes reached a maximum intensity of XI.
Earthquakes of large magnitude do not necessarily cause the most intense surface effects. The effect in a given region depends to a large degree on local surface and subsurface geologic conditions.
An area underlain by unstable ground sand, clay, or other unconsolidated materials , for example, is likely to experience much more noticeable effects than an area equally distant from an earthquake's epicenter but underlain by firm ground such as granite. In general, earthquakes east of the Rocky Mountains affect a much larger area than earthquakes west of the Rockies. An earthquake's destructiveness depends on many factors. In addition to magnitude and the local geologic conditions, these factors include the focal depth, the distance from the epicenter, and the design of buildings and other structures.
The extent of damage also depends on the density of population and construction in the area shaken by the quake.
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