Fascinating! Hurricane Sandy caused seismic waves into the interior of US,
due to intense wave action against the continent and also waves hitting waves.
Katrina caused seismic action measurable in California.
"The energy generated by Sandy is going to be used to image the crust and upper mantle under North America," says Koper, noting that Earthscope uses years of seismic data to construct images. "We are using seismic waves created by ocean waves to make images of the continent."
Normal ocean waves "decay with depth very quickly," says Koper. But when Sandy turned, there was a sudden increase in waves hitting waves to create "standing waves" like those created when you throw two pebbles in a pond and the ripples intersect. "Pressure generated by standing waves remains significant at the seafloor," he says.
"When Sandy made that turn to the northwest, although wind speeds didn't get dramatically bigger, the seismic energy that was created got tremendously bigger because the ocean's standing waves were larger from the wave-wave interaction," he adds.
Not only did the seismic waves become more energetic, "but the periods got longer so, in a sense, the sound of those seismic waves got deeper -- less treble, more bass -- as the storm turned," Koper says.