Enlarged Views (mbLg Wave Magnitude, 0^o to 4^o Distance)

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

Fig. (b) Extracted seismogram for the Evansville earthquake containing the P arrival and the Lg wave arrivals.

Fig. (c) Close-up of the Lg wave arrivals for the Evansville earthquake and example amplitude and period measurements.

Example:

D = 2.59 degrees

   A = 1250 digital units

   T = 2 seconds    

mbLg = 5.0   

          The official USGS mbLg magnitude is 5.3.  Check to see that the calculator works with these values.