Enlarged Views (Surface Wave Magnitude)

Fig. (a) AmaSeis 24-hr record showing the Sakhalin Island earthquake.

Fig. (b) Extracted seismogram for the Sakhalin Island earthquake showing the P wave and surface wave arrivals.

Fig. (c) Close-up of the Surface waves for the Sakhalin Island earthquake and example amplitude (A) and period (T) measurements.

Example:

D = 81.08 degrees

A = 48 digital units

T = 20 seconds   

MS = 7.0            

          The official USGS MS magnitude is 7.1. Check to see that the calculator works with these values.