Did someone just test a nuclear bomb? Seismometers can detect anything that shakes the ground, so seismologists have to use many techniques to determine the cause. In this animation we look at both seismograms and focal mechanisms and how their signatures can differentiate between an earthquake and a bomb.
The "moment magnitude" scale has replaced the Richter scale for large earthquakes. Scientists have developed far-more sensitive seismometers that, with faster computers, have enabled them to record & interpret a broader spectrum of seismic signals than was possible in the 1930's, when the Richter magnitude was developed. Find out what scientists learn from seismograms.
Why do seismologists change the magnitude of an earthquake? Obtaining an accurate preliminary magnitude can be difficult due not only to the complex processes that occur deep within the Earth, but because there are over a dozen techniques of for calculating the magnitude of an earthquake.
The focal mechanism of an earthquake is represented by a “beachball” diagram. These are released after an earthquake to illustrate the type of faulting produced the earthquake. This difficult concept is carefully explained using strike-slip, normal, and thrust faults.
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