User:Erbudania/sandbox

Q1 Why are surface waves more destructive to buildings than P waves or S waves are?ans Because surface waves have a larger amplitude and thus more energy and so can cause more damage than P and S waves.

Q2 An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock. Aftershocks are formed as the crust around the displaced fault plane adjusts to the effects of the main shock

Foreshock activity has been detected for about 40% of all moderate to large earthquakes,[2] and about 70% for events of M>7.0.[3] They occur from a matter of minutes to days or even longer before the main shock, for example the 2002 Sumatra earthquake is regarded as a foreshock of the 2004 Indian Ocean earthquake with a delay of more than two years between the two events.[4]

When a fault ruptures, seismic waves are propagated in all directions, causing the ground to vibrate at frequencies ranging from about 0.1 to 30 Hertz. B'''uildings vibrate as a consequence of the ground shaking; damage takes place if the building cannot withstand these vibrations. Compressional and shear waves mainly cause high-frequency (greater than 1 Hertz) vibrations which are more efficient than low-frequency waves in causing low buildings to vibrate. Rayleigh and Love waves mainly cause low-frequency vibrations which are more efficient than high-frequency waves in causing tall buildings to vibrate. Because amplitudes of low-frequency vibrations decay less rapidly than high-frequency vibrations as distance from the fault increases, tall buildings located at relatively great distances (60 miles) from a fault are sometimes damag'''ed.