Difference of similar magnitude earthquakes in CA vs Midwest

In light of today's earthquake in Virginia, I thought it would be interesting to share this illustration that shows the difference of area that a 6.8 magnitude earthquake impacts in California vs. the New Madrid fault in SE Missouri/West Tennessee. Today's earthquake was reportedly felt as far away as Cincinnati, OH. The wiki link below gives some technical explanations why earthquake waves can travel so much farther in the eastern part of the U.S. compared to the west coast. Basically, it's all about the type of foundation: the soil, the bedrock, and the depth below ground of the initial shock.

http://upload.wikimedia.org/wikipedia/commons/2/2c/NMSZ_Vergleich.jpg

http://en.wikipedia.org/wiki/New_Madrid_Seismic_Zone