A strange deep earthquake has been detected for the first time on the ocean floor in Japan, the origin of which has been traced to a major storm between Greenland and Iceland.
The findings could help experts learn more about Earth's internal structure and improve the detection of earthquakes and ocean storms.
The storm that caused the deep shaking was a "weather bomb" that struck over the North Atlantic. It was a small but powerful storm in which the pressure quickly creates a more vigorous storm.
As the storm unfolded, resulting waves hit the ocean floor between Greenland and Iceland. These subtle waves propagated through the Earth and could be detected in remote places.
The researchers used seismic equipment at 200 locations both on land and on the seafloor in Japan to track the tremors. Their readings showed that they were secondary wave microseisms (S), or very weak tremors.
Unlike primary (P) waves, which are generally detected during major hurricanes, G waves are slow, and only move through rock. This is the first time that scientists have observed an S wave.
In an article published in Science, Peter Gerstoft and Peter Bromirski of the University of California, San Diego say that this discovery provides seismologists with a new tool with which to study the deepest structure of the Earth.
Even if the tremors in Japan were not an earthquake, the results could improve understanding of the Earth's inner core, and could be used to improve the detection of earthquakes in the future.