Slow-Motion Earthquake Captured: A Tectonic Shock Absorber Off Japan

For the first time, scientists have directly observed a slow-slip earthquake releasing tectonic pressure on a major ocean fault. The event, occurring on the tsunami-generating portion of Japan's Nankai Trough, acted like a tectonic shock absorber, slowly unzipping the fault line between tectonic plates. Deep-sea borehole sensors captured two such events in 2015 and 2020, each lasting weeks and traveling tens of kilometers along the fault. The study reveals these slow slips occur in areas of abnormally high fluid pressure, confirming the role of fluids in slow earthquakes. This discovery provides crucial insights into subduction zone behavior throughout the Pacific Ring of Fire, highlighting the contrast with potentially more hazardous faults like Cascadia, which lacks this natural shock-absorbing mechanism.