Large body of water found in Earth's mantle

A seismologist at Washington University in St. Louis has made the first 3-D model of seismic wave damping diminishing deep in the Earth's mantle and has revealed the existence of an underground water reservoir at least the volume of the Arctic Ocean. It is the first evidence for water existing in the Earth's deep mantle. Michael E. Wysession, Ph.D., Washington University professor of earth and planetary sciences in Arts & Sciences, working with former graduate student Jesse Lawrence (now at the University of California, San Diego), analyzed 80,000 shear waves from more than 600,000 seismograms and found a large area in Earth's lower mantle beneath eastern Asia where water is damping out, or attenuating, seismic waves from earthquakes. The traditional method seismologists use to image the Earth below us is to measure the speed of seismic waves. This will provide a sort of CAT scan of the Earth's core and mantle. Using wave speeds alone is a problem, however, because they cannot distinguish between temperature and composition variations. The research is described in a forthcoming monograph, Earth's Deep Water Cycle, which is in press to be published by the American Geophysical Union.
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