Enlarged Views (mbLg Wave Magnitude, 4^o to 30^o Distance)

Fig. (a) AmaSeis 24-hr record showing the NE Alabama Earthquake.

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

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

Example:

D = 6.05 degrees

   A = 770 digital units

   T = 1.5 seconds    

mbLg = 5.3    

          The official USGS mbLg magnitude is 4.9. Check to see that the calculator works with these values.