USGS
Hawaiian Volcano Observatory

Kilauea

Mauna Loa

Earthquakes

Other Volcanoes

Volcanic Hazards

Procedure for calculating local magnitude, ML

from Earthquakes by Bruce A. Bolt (W.H. Freeman and Company, 1988).



  1. Measure the distance to the focus using the time interval between the S and the P waves (here S-P = 24 seconds).
  2. Measure the height of the maximum wave motion on the seismogram (23 millimeters).
  3. Place a straight edge between the appropriate points on the distance (left) and amplitude (right scales to obtain magnitude ML = 5.0.

HomeVolcano WatchProductsPhoto GalleryPress Releases
How Hawaiian Volcanoes Work

The URL of this page is http://hvo.wr.usgs.gov/
Contact: hvowebmaster@usgs.gov
Updated :