Douglas A. Wiens

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Shear-wave splitting analysis of local events recorded on land and on the ocean floor in the Tonga arc and Lau backarc indicate a complex pattern of azimuthal anisotropy that cannot be explained by mantle flow coupled to the downgoing plate. These observations suggest that the direction of mantle flow rotates from convergence-parallel in the Fiji plateau to(More)
[1] Mantle dynamics can strongly affect melting processes beneath spreading centers and volcanic arcs. A 2-D numerical model of the Tonga subduction zone, with the slab viscously coupled to the mantle beneath the brittleductile transition but faulted above, shows that induced corner flow may cause asymmetric melting at the Lau backarc spreading center, 400(More)
Long-period seismic sources associated with glacier motion have been recently discovered, and an increase in ice flow over the past decade has been suggested on the basis of secular changes in such measurements. Their significance, however, remains uncertain, as a relationship to ice flow has not been confirmed by direct observation. Here we combine(More)
[1] The horizontal components of broadband seismographs are highly sensitive to tilt, suggesting that commonly deployed portable broadband seismic sensors may record important tilt information associated with volcanic eruptions. We report on a tilt episode that coincides with the first historical eruption of Anatahan volcano on May 10, 2003. The tilt was(More)
We have obtained constraints on the strength and orientation of anisotropy in the mantle beneath the Tonga, southern Kuril, Japan, and Izu-Bonin subduction zones using shear-wave splitting in S phases from local earthquakes and in teleseismic core phases such as SKS. The observed splitting in all four subduction zones is consistent with a model in which the(More)
The mantle wedge of a subduction zone is characterized by low seismic velocities and high attenuation, indicative of temperatures approaching the solidus and the possible presence of melt and volatiles. Tomographic images show a low velocity region above the slab extending from 150 km depth up to the volcanic front. The low velocities result at least(More)
[1] The anelastic structure of a subduction zone can place first-order constraints on variations in temperature and volatile content. We investigate seismic attenuation across the western Pacific Mariana subduction system using data from the 2003–2004 Mariana Subduction Factory Imaging Experiment. This 11-month experiment consisted of 20 broadband stations(More)
We have identified three groups of deep earthquakes showing nearly identical waveforms in the Tonga slab. Relocation with a cross-correlation method shows that each cluster is composed of 10 to 30 earthquakes along a plane 10 to 30 kilometers in length. Some of the earthquakes are colocated, demonstrating repeated rupture of the same fault, and one pair of(More)
s for the 13 Annual IRIS Workshop June 6-9, 2001 Jackson Lake Lodge, Moran, Wyoming LOCATIONS OF MID-OCEANIC EARTHQUAKES CONSTRAINED BY SEAFLOOR BATHYMETRY Jianfeng Pan, Michael Antolik, and Adam M. Dziewonski Department of Earth and Planetary Sciences Harvard University, Cambridge, MA 02138 (617) 496-8364 jpan@seismology.harvard.edu Earthquakes associated(More)