Scientists have detected an elusive kind of seismic wave, the S wave, and managed for the first time to trace the source of the tremor. For the first time, scientists have tracked an unusual type of deep-Earth tremor which could help them to understand more about the inner structure of the Earth, and improve detection of earthquakes and oceanic storms. Researchers in Japan used a network of seismic sensors to observe S waves with a velocity of 20 to 22.2 km per second, which originated from a rapidly strengthening cyclone over the North Atlantic Ocean, off the coast of Greenland. These waves are typically lost within Earth's seismic background noise. However, the researchers found the waves by combining and analyzing data from 202 extra-sensitive seismic stations in Japan. "Using a seismic array in Japan, we observed both P and S wave microseisms excited by a severe distant storm in the Atlantic Ocean," Kiwamu Nishida and Ryota Takagi reported in their paper, published in the Science