1.

Certain Earthquakes Have A Negative Magnitude, Is This An Error?

Answer»

No, it is not an error. As magnitude calculations are BASED on a logarithmic scale, a ten-fold drop in amplitude decreases the magnitude by 1. Let us assume that on a seismogram:

  • Amplitude of 20 MILLIMETERS corresponds to a magnitude 2 earthquake.
  • 10 times less (2 millimeters) corresponds to a magnitude of 1;
  • 100 times less (0.2 millimeters) corresponds to magnitude 0;
  • 1000 times less (0.02 millimeters) corresponds to magnitude -1.

Naturally, a negative magnitude is found only for very small events, which are not FELT by humans.

No, it is not an error. As magnitude calculations are based on a logarithmic scale, a ten-fold drop in amplitude decreases the magnitude by 1. Let us assume that on a seismogram:

Naturally, a negative magnitude is found only for very small events, which are not felt by humans.


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