Answer : The National Earthquake Information Center now locates about 20,000 earthquakes around the globe each year, or approximately 55 per day. As a result of the improvements in communications and the increased interest in natural disasters, the public now learns about earthquakes more quickly than ever before.
Scientists analyzed the historical record of earthquakes greater than 8.0 in magnitude and concluded that the global frequency of large earthquakes is no higher today than it has been in the past The vibrations of engineering significance occur at frequencies from less than 0.2 Hz to 20 Hz (periods from about 5 seconds down to about 0.05 seconds). This is just below the range of ordinary sound vibrations.
