Finite-frequency wave propagation through outer rise fault zones and seismic measurements of upper mantle hydration
Effects of serpentine-filled fault zones on seismic wave propagation in the upper mantle at the outer rise of subduction zones are evaluated using acoustic wave propagation models. Modeled wave speeds depend on azimuth, with slowest speeds in the fault-normal direction. Propagation is fastest along faults, but, for fault widths on the order of the seismic wavelength, apparent wave speeds in this direction depend on frequency. For the 5–12 Hz Pn arrivals used in tomographic studies, joint-parallel wavefronts are slowed by joints. This delay can account for the slowing seen in tomographic images of the outer rise upper mantle. At the Middle America Trench, confining serpentine to fault zones, as opposed to a uniform distribution, reduces estimates of bulk upper mantle hydration from ~3.5 wt % to as low as 0.33 wt % H2O.
Citation Information
Publication Year | 2016 |
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Title | Finite-frequency wave propagation through outer rise fault zones and seismic measurements of upper mantle hydration |
DOI | 10.1002/2016GL070083 |
Authors | Nathaniel C. Miller, Daniel Lizarralde |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Geophysical Research Letters |
Index ID | 70176415 |
Record Source | USGS Publications Warehouse |
USGS Organization | Woods Hole Coastal and Marine Science Center |