Lets plot the LLg amplitudes for these two EQs.
This graph shows amplitudes for LLg waves recorded by OhioSeis stations for the 2003.06.30 & 2004.06.30. Amplitudes are plotted in "digital units". The microseism noise amplitudes for these day are around 20 du, hence we have good signal-to-noise ratio.
Since the 2003 EQ is larger, the two EQs are plotted with different y-axis scales so that we can better compare the distance decay. The best-fit lines for a power law between distance and LLg amplitude are also plotted. Notice that the overall log slope decay isabout -1.5, a similar value was found for the large 2001 EQ.
This consistent behavior, and the fact that the assumed spatial decay for the MN formula is a log slope of -.90, argues that we should develop a modified formula for the NE Ohio LLg magntiude.