Seismic waves reflected from Earth’s core moved parts of Japan 5 mm east
Shift followed the 2011 Tohoku-Oki earthquake and represents a new type of seismic hazard The post Seismic waves reflected from Earth’s core moved parts of Japan 5 mm east appeared first on Physics World .
Parts of Japan unexpectedly shifted eastward by up to 5 millimeters in the minutes following the 2011 Tohoku-Oki earthquake, as revealed by a new study. This seismic shift, previously unrecognized, was caused by seismic waves traveling from Earth's core back to the surface, a phenomenon previously linked to imaging techniques deep within the planet.
The 9.0 magnitude earthquake struck the boundary between the Pacific and North American tectonic plates off the coast of Japan, causing widespread damage and triggering a devastating tsunami. Researchers from the University of Chicago studied shear waves recorded by Japan's dense network of Global Navigation Satellite System instruments, discovering ScS waves that travelled through the Earth, bounced off the core-mantle boundary, and returned almost simultaneously 13 minutes after the main shock.
While ScS waves have been studied for imaging the deep Earth, this study represents the first evidence of their capability to trigger significant displacement caused by slip after an earthquake, suggesting the need for researchers to account for these waves to fully understand the consequences of seismic ruptures on both the surface and deep within tectonic plates.
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