The subduction zone off the east coast of the archipelago racks up more intermediate-depth and deep earthquakes than any other subduction zone, where one plate of Earths lithosphere dives under another, on the planet. Analyzing data from several seismic surveys with both ocean bottom seismometers and island-based seismic stations, they were surprised to find a zone of intense earthquake activity in the downgoing slab, which they call a seismic belt.
It looks like the seismic belt is produced by the sudden flushing of water when the slab warms up enough that the hydrated minerals can decompose and give off their water, said Doug Wiens, the Robert S. Brookings Distinguished Professor of earth and planetary sciences in Arts & Sciences at Washington University. Where the double seismic zone started to break down in Tonga, however, we saw this really active area of earthquakes that we named the seismic belt, Wiens said. The faster the slab was moving, the deeper the earthquakes, and the slower the slab, the shallower the earthquakes. https://www.sciencedaily.com/releases/2017/01/170111151428.htm
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February 2017
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