My house is about 250 miles from the Virginia earthquake epicenter. Based on well driller's experience in this area, solid granite is about 60 feet below the surface here. I have Superior Walls foundation/basement with units 10' high. The house is two story. I was upstairs when the quake struck. Some items rattled and everything on a table or desk shook visibly. I assume that the upstairs moved more than the downstairs. About half of my basement is daylight with site-laid brick face on the Superior Walls. I have found no cracks in the brick work. Based on the accounts of two neighbors who have concrete block foundations, their houses must have shaken comparably to mine. I had wondered how Superior Walls would react and fare in an earthquake. Since I was only at one place, my conclusions are not perfect. But it looks as if the SW works OK with these tremors. The bolts initially installed to hold the wall units together are not the forces holding the walls after construction is PROPERLY completed.