Earthquake+(seismic)+waves

Earthquake (seismic) waves  seismic waves are waves of force that travel through the Earth or other elastic bodies, for example as a result of an earthquake, explosions, or some other precess that imparts the forces. Seismic waves are measured by a seismograph, which records the output of a seismometer (their magnitude, size, time etc,.). A seismograph (seismometer) is the device or an instrument that scientists use to measure earthquake. There are mainly two waves for an earthquake, body waves and surface waves. P wave (primary waves) is what is caught in by the seismograph and it comes before the actual shake, S waves (secondary waves). P waves are capable of reaching people because it can travel 8 kilometers per a second (28,800km/hr) and it can travel through any type of materials. Moreover, in air, these pressure waves take the form of sound waves, hence they travel at the rate of speed of sound (mach). The S waves are transverse waves, which means that the ground is displaced perpendicularly to the direction of propagation. They can usually travel at the rate of 5 kilometers per a second (18,000km/hr). S waves can only travel through solids, hence S waves cannot propagte in the liquid part of the earth, such as oceans and lakes. The speed is about 60% of that of P waves in the given material. The third general type of earthquake wave is called as “surface wave”, reason being is that its motions are limited near the ground surface. This wave makes the the surface of water move. There are two types of surface waves in an earthquake – Love wave and Rayleigh wave. Love waves are surface waves that cause horizontal shearing of the ground. They usually traveling slightly faster than the Rayleigh waves, about 90% of the S wave velocity. Rayleigh waves, also known as ground roll (like rolling ocean waves), are surface waves that travel both vertically and horizontally in a vertical plane pointed in the direction in which the waves are traveling. http://www.eserc.stonybrook.edu/ProjectJava/Quake/home21.html - If you go in to this website, there is a simple applet that you can use to calculate and simulate the arrival time of Primary waves and Second waves from a position and can find the epicenter of three earthquakes.