Rattled doors in Washington, DC and rang bells in Boston. Strongest earthquake to hit US this century. Ground flowed due to liquifaction of the soil. They became thixotropic , a term used to refer to a solid that flows when vibrated or jolted. Landslides or earthflows occurred.
Thixotropic sediment causes ground to flow Tsunami - seismic sea waves.
When they enter shallow water, they slow down, the water stacks up. Earthquake Prediction Monitor to look for patterns Parkfield, California had earthquakes every 22 years in anticipation of the next one, seismographs were put into place, but it has not yet occurred. Changes in animal behavior Radio wave emissions from the Earth - first noticed 1989 San Francisco.