In March 1996 an intense swarm of volcano-tectonic earthquakes (-3000 felt by local residents, A/max5.1, cumulative moment of 2.7 x 10 •8 N m) beneath Akutan Island in the Aleutian volcanic arc, Alaska, produced extensive ground cracks but no eruption of Akutan volcano. Synthetic aperture radar interferograms that span the time of the swarm reveal complex island-wide deformation: the western pa...

The strong association of iodine with organic material and the presence of the cosmogenic radioisotope I make the iodine isotopic system useful in tracing and dating studies of organic materials and their derivatives. We present here results from two new applications of this system, investigations of gas hydrates from the Peru Margin (ODP 201, Site 1230) and of fluids collected from the fore ar...

[1] Peridotitic xenoliths in basaltic andesites from Batan island in the Luzon arc contain silica-rich (broadly dacitic) hydrous melt inclusions that were likely trapped when these rocks were within the upper mantle wedge underlying the arc. These melt inclusions have been previously interpreted to be slab-derived melts. We tested this hypothesis by analyzing the oxygen isotope compositions of ...

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 lower transition zone (520–660 km) an...