Plate boundaries may experience higher temperatures and pressures than we thought

Source: Geochemistry, Geophysics, Geosystems

Temperature and shear stress are two influential variables that affect faulting and seismicity. Sub-Zones, where the tectonic plates meet. Because earthquakes occur at plate boundaries tens of kilometers below the Earth's surface, the effects of temperature and stress magnitude are poorly understood and hotly debated.

England and others. Examine these variables along the plate boundary in the north Honshu, Japan's largest island and the devastating 2011 Tohoku earthquake—the most powerful earthquake ever recorded in Japan. The authors used a dense set of collected heat flux measurements 100 meter deep bore wells As a proxy for measurements on an inaccessible plate interface.

Their mathematical analysis found the temperature at a depth of 60 kilometers at the plate boundary to be about 660 degrees Celsius. shear stress 100 is approx megapascals. Both figures, especially the temperature estimates, have a degree of uncertainty due to the difficulty in determining the contribution of radiogenic heating. But both are significantly higher than past estimates, which were typically less than about 400 degrees Celsius and a few tens of megapascals, respectively. However, the results are consistent with a heat flux analysis Kermadec Sub-ZoneThis is the only place where shear stress has been estimated using a comparable density of surface measurements where the uncertainty of radiation influence is significantly lower.

The results improve understanding of the conditions surrounding earthquakes along the northern Honshu plate boundary. Additionally, they explain the temperature and pressure found in rocks Chanbakawa Belt In southwestern Japan, a 90-million-year-old plate interface was discovered. As the authors note, the agreement of the results with conditions at the present-day interface supports the contention that the Sanbhagawa-like memorial plate boundaries record the physical and chemical conditions for earthquake formation in contemporary subduction zones. (Geochemistry, Geophysics, Geosystems, https://doi.org/10.1029/2023GC0112852024)

—Aaron Siddar, science writer

Quote: Siddar, A. (2024), plate boundaries may experience higher temperatures and pressures than we thought, EOS, 105, https://doi.org/10.1029/2024EO240077. Published on 21 February 2024.

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