October 2001: Research Proposal summary, full text available as a PDF file:

US-JAPAN COLLABORATIVE RESEARCH: MULTI-SCALE SEISMIC IMAGING OF THE MARIANA SUBDUCTION FACTORY

Principal Investigators:
B. Taylor, G. Moore, A. Goodliffe, P. Fryer: SOEST U. Hawaii
D. Wiens, G. Smith: Washington U. St. Louis
S. Klemperer: Stanford U. J. Hildebrand: SIO UCSD
K. Suyehiro, S. Kodaira: JAMSTEC
H. Shiobara: ERI U. Tokyo
A. Taira: ORI U. Tokyo
N. Seama: Kobe U.

We propose to carry out marine multi-channel seismic reflection, controlled-source wide-angle reflection/refraction, and passive recording of local and teleseismic earthquakes to provide a comprehensive velocity, attenuation, structural and stratigraphic image of the Mariana island-arc system, from the subducting Pacific Plate to the backarc, at 15° to 18°N. This will be the first completely integrated seismic study of any active arc.

Principal objectives are to determine:

• the velocity and attenuation structure of the mantle as a proxy for temperature/ partial melting of the mantle wedge below the backarc spreading center and the active arc and for hydration and metamorphism below the forearc;
• the large-scale pattern of flow in the mantle wedge, as reflected by seismic anisotropy, which controls the mantle magma supply to the arc and back-arc;
• the precise location and velocity structure of subducting oceanic crust, which will place constraints on the depth of various devolatization/metamorphism reactions and the basalt-eclogite transformation;
• the velocity and density structure of the crust as a proxy for the composition of an intra-oceanic arc, with implications for models of continental growth and crustal recycling to the mantle;
• the seismic stratigraphy and structure of the forearc, arc and remnant arc which, calibrated by existing drill hole data, record a 50 m.y. history of intra-oceanic sedimentation, magmatism and deformation involving subduction initiation, episodic arc volcanism - rifting - back-arc spreading, and serpentinite diapirism. othe possible identification of magma chambers below active volcanoes and of the conduits beneath forearc serpentinite seamounts;
• the possible existence of an intermediate depth double seismic zone and the relationship between slab seismicity and island arc volcanism; othe updip and downdip limits of the seismogenic zone and implications for the largely aseismic subduction in the Mariana convergent margin.

Full proposal text, with figures, as a PDF file (3.6 MB)