Enlarged Views (Body Wave Magnitude)

Fig. (a) AmaSeis 24-hr record (screen display) for the Iceland Earthquake.

Fig. (b) Extracted seismogram of the Iceland earthquake containing the P arrival and the surface wave arrivals.

Fig. (c) Close-up of the P-wave arrival for the Iceland earthquake and example amplitude (A) and period (T) measurements.

Example:

D = 44.23 degrees

A = 48 digital units

T = 2 seconds     

mb = 5.8            

          The official USGS mb magnitude is 6.1. Check to see that the calculator works with these values.