Earthquakes on the East Coast can be felt at a great distance and can cause more pronounced shaking in comparison to those on the West Coast because rocks in the region are often older, harder and more dense.
“These are competent rocks that transmit energy well,” Simons said.
I don’t remember exactly where I read it originally, but this article says something similar: https://www.nbcnews.com/science/science-news/earthquake-shakes-us-east-coast-rcna146575