![]() ![]() ![]() This new study delves deeper into the relationship between slow-slip events and larger, felt earthquakes along a subduction zone running parallel to the northeastern coast of Japan. They have long suspected a connection between those events and earthquakes, but if and how the two are related has remained a mystery. Seismologists have observed slow-slip events in the days following large earthquakes. These events happen so slowly that the energy equivalent of a magnitude 6.5 event can occur over the course of a month-without anyone even feeling it. Pacific Northwest, for instance, seismologists detect slow-slip events about once every 15 months. In the Cascadia Subduction Zone off the U.S. Rather, scientists track the small, slow movements by recording the motion of GPS receivers buried in the ground. Slow slip does not produce seismic waves, so seismometers cannot observe it. Get the most fascinating science news stories of the week in your inbox every Friday. Such aseismic motions occur over weeks or months, unlike earthquakes, which happen in seconds. ![]() In this study, Uchida and his colleagues investigated those events where the Pacific Plate, an oceanic slab of the Earth’s crust, creeps underneath the continental Okhotsk Plate. Slow-slip or “aseismic” events can occur at any plate boundary but are observed most clearly in subduction zones. When slow-slip events occur, “the possibility of earthquakes higher than normal” because of the stress from the slow-slip events, said Naoki Uchida, lead author on the paper and a seismologist at Tohoku University in Sendai, Japan. ![]() The new insight, published online on 28 January in Science, may help scientists better forecast the likelihood of large earthquakes. Scientists studying the massive subduction zone off the east coast of Japan have found a correlation between earthquakes and periodic events called “slow slip” wherein the plate moves but the motion produces no discernable seismic signature. ![]()
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