Scientists capture slow-motion earthquake in action

Summary

Tectonic setting around Japan. Centroid Moment Tensor solution shows the mechanism of the 2024 Hyuga-nada earthquake (b) Pre-seismic SSE (contour interval: 5 cm) 10 July, 2023–6 August, 2024. Pre-slip with Mw6.0 was detected in the down dip extension of the 2024 Hyuga-nada earthquake, Japan, from late 2023. (c) Cumulative moment of the rectangular area in (B). The recurrence interval of SSE was shortened to one year from an average of two years right before the earthquake, consistent with simulations where the weakening of the megathrust was attributed to the cause. Credit: Shinzaburo Ozawa Epicenter data from the Japan Meteorological Agency Scientists for the first time have detected a slow slip earthquake in motion during the act of releasing tectonic pressure on a major fault zone at the bottom of the ocean. The slow earthquake was recorded spreading along the tsunami-generating portion of the fault off the coast of Japan, behaving like a tectonic shock absorber. Researchers from The University of Texas at Austin described the event as the slow unzipping of the fault line between two of the Earth's tectonic plates. Their results were published in Science. "It's like a ripple moving across the plate interface," said Josh Edgington, who conducted the work as a doctoral student at the University of Texas Institute for Geophysics (UTIG) at UT Austin's Jackson School of Geosciences. Slow slip earthquakes are a type of slow-motion seismic event that takes days or weeks to unfold. They are relatively new to science and are thought to be an important process for accumulating and releasing stress as part of the earthquake cycle. The new measurements, made along Japan's Nankai Fault, appear to confirm that. This breakthrough research was made possible by borehole sensors that were placed in the critical region far offshore, where the fault lies closest to the seafloor at the ocean trench. Sensors installed in boreholes can detect even the slightest motions—as small as a fe...