A Seismic Wave from Japan's 2011 Earthquake Triggered a Global Shift A seismic wave generated by Japan's 2011 magnitude-9 Tohoku-Oki earthquake traveled nearly 2,900 kilometers into Earth's core, bounced off the outer core, and returned to the surface 13 minutes later, causing Japan to shift eastward by approximately six millimeters. This phenomenon, the first of its kind ever recorded, was identified by researchers analyzing GPS data from the earthquake, which had been unresolved for over a decade. For 15 years following the 2011 disaster, a small anomaly in GPS data remained unexplained. Approximately 15 minutes after the main shock struck off Japan's northeastern coast, GPS stations across the country registered a step-like eastward displacement of five to six millimeters. The shift was too minor to be felt by people or cause damage, and it did not align with any known aftershocks. Despite being noted in subsequent data compilations, the signal remained uninterpreted until a 2026 study by a team led by Sunyoung Park, an assistant professor at the University of Chicago, provided a groundbreaking explanation. The team concluded that the displacement was caused by an ScS wave—a shear wave that traveled downward from the earthquake's epicenter, reflected off the core-mantle boundary at approximately 2,890 kilometers depth, and returned to the surface as a shear wave. The reflection occurred because shear waves cannot propagate through liquid, and Earth's outer core is composed of molten iron and nickel. The wave's round-trip journey took about 13 minutes, arriving simultaneously across Japan and triggering small additional slip on already-stressed megathrust interfaces along the country's tectonic plate boundaries. The slip event, though minor, released energy equivalent to a magnitude-7.5 earthquake.#japan #university_of_chicago #sunyoung_park #tohoku_earthquake #scs_wave
Seismic Event Shifted Japan's Tectonic Plates, Study Reveals A newly identified seismic phenomenon, triggered by the 2011 Tohoku earthquake, has revealed that Japan’s tectonic plates shifted permanently eastward by a fraction of an inch. This discovery, detailed in a study led by University of Chicago geophysicist Sunyoung Park, challenges existing understanding of how seismic waves interact with Earth’s core and reshape geological structures. The event, which occurred 15 minutes after the magnitude 9.0 earthquake struck on March 11, 2011, was detected through GPS data showing a uniform eastward movement across mainland Japan, from Hokkaido to Kyushu. The shift, measuring 5 to 6 millimeters, was initially dismissed as a data anomaly but gained attention when Park analyzed the patterns. She noted that the movement did not align with the timing of the initial earthquake or its aftershocks, suggesting a deeper, previously undocumented process. According to the study, seismic waves from the earthquake traveled through Earth’s core, rebounded, and returned to the crust, displacing four major tectonic plates. This “core-visiting” wave, which took about 15 minutes to complete its journey, reactivated fault lines and triggered movement along distant plate boundaries, including the intersections of the Pacific and Okhotsk plates, as well as the Philippine Sea and Eurasian plates. Park’s findings highlight a novel mechanism by which earthquakes can influence geological systems long after the main rupture. While traditional aftershocks are localized and unpredictable, this event’s round-trip journey to the core and back allowed for a broader, albeit less intense, displacement. The energy released during this process equated to a 7.#columbia_university #university_of_chicago #sunyoung_park #tohoku_earthquake #goran_ekstrom
