People who came out on the street after an earthquake look up at a window that cracked during the quake on Market Street in Philadelphia, Tuesday, Aug. 23, 2011. A 5.9 magnitude earthquake centered northwest of Richmond, Va., shook much of Washington, D.C., and was felt as far north as Rhode Island, New York City and Martha's Vineyard, Mass., where President Barack Obama is vacationing. (AP Photo/Alex Brandon)