When Superstorm Sandy turned and took aim at New York City and Long Island last October, ocean waves hitting each other and the shore rattled the seafloor and much of the United States–shaking that was detected by seismometers across the country. (NOTE: Subscribers can still listen to this program on earthquake prediction.)
Seismologist Keith Koper says, "We detected seismic waves created by the oceans waves both hitting the East Coast and smashing into each other."
The shaking was caused partly by waves hitting the East Coast, but much more by waves colliding with other waves in the ocean, setting up "standing waves" that reach the seafloor and transmit energy to it.
While many people may not realize it, earthquakes are not the only events that generate seismic waves. So do mining and mine collapses; storm winds, waves and tornadoes; traffic, construction and other urban activities; and meteors hitting Earth.
Geologist Oner Sufri says, "We were able to track the hurricane by looking at the ‘microseisms’ [relatively small seismic waves] generated by Sandy. As the storm turned west-northwest, the seismometers lit up."
Sandy did not create enough of a seismic event to trigger major earthquakes, but the fact that seismometers across the United States reacted to the storm is a testament to its power. Sandy did not generate the highest winds ever recorded, but it was one of the largest hurricanes in terms of its size, and the way it came ashore caused it to generate very large waves.
Could Sandy happen again? It came ashore as far north as it did and as late in the season as it did because the waters of the mid-Atlantic were much warmer than normal, enabling it to move far to the north and gain power as it bore down on New York.