Date: 2024-06-26
In some subduction zones, intermediate-depth earthquakes (~70–300 km depth) occur along two separate planes, known as double seismic zones. The subduction system in eastern Taiwan has a similar feature with shallower double seismic zone. Mechanisms forming such intriguing seismicity, however, remain inconclusive. The research, led by Dr. Wen-Pin Hsieh, Research Fellow at the Institute of Earth Sciences, Academia Sinica, has precisely measured the thermal conductivity of antigorite, an important serpentine mineral in subducting slabs, at high pressure-temperature conditions along slab subduction. The study demonstrated that antigorite has a strong thermal conductivity anisotropy. Combined with numerical modeling on slab’s thermal evolution, the team further showed that such strong thermal conductivity anisotropy combined with shear-induced crystal-preferred-orientation creates a thermal blanket effect that suppresses heat flow, significantly affecting slab’s thermal evolution and promoting dehydration embrittlement. Meanwhile, such effect also facilitates thermal runaway, a positive feedback accumulating heat, to trigger intermediate-depth earthquakes. These exciting findings highlight the important role that hydrous minerals play on the thermal state of a slab and the fundamental mechanisms triggering deep earthquakes. This research has been published on June 18, 2024 in Nature Communications. The first author of this research, Yu-Hsiang Chien, is a PhD candidate of TIGP-ESS at Academia Sinica, and coauthors include Yi-Chi Tsao of IES, and Dr. Enrico Marzotto of GeoForschungsZentrum (GFZ), Germany.
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