AN: T72A-1229
TI: Multi-Channel Seismic Images of the Mariana Forearc: EW0202 Initial Results
AU: * Oakley, A J
EM: aoakley@hawaii.edu
AF: SOEST, University of Hawaii at Manoa, 1680 East West Rd., Honolulu, HI 96822
AU: Goodliffe, A M
AF: SOEST, University of Hawaii at Manoa, 1680 East West Rd., Honolulu, HI 96822
AU: Taylor, B
AF: SOEST, University of Hawaii at Manoa, 1680 East West Rd., Honolulu, HI 96822
AU: Moore, G F
AF: SOEST, University of Hawaii at Manoa, 1680 East West Rd., Honolulu, HI 96822
AU: Fryer, P
AF: SOEST, University of Hawaii at Manoa, 1680 East West Rd., Honolulu, HI 96822
AB: During the Spring of 2002, the Mariana Subduction Factory was surveyed using multi-channel seismics (MCS) as the first major phase of a US-Japanese collaborative NSF-MARGINS funded project. The resulting geophysical transects extend from the Pacific Plate to the West Mariana remnant arc. For details of this survey, including the results from the back-arc, refer to Taylor et al. (this session). The incoming Pacific Plate and its accompanying seamounts are deformed by plate flexure, resulting in extension of the upper crust as it enters the subduction zone. The resultant trench parallel faults dominate the bathymetry and MCS data. Beneath the forearc, in the southern transects near Saipan, the subducting slab is imaged to a distance of 50-60 km arcward. In addition to ubiquitous trench parallel normal faulting, a N-S transect of the forearc clearly shows normal faults perpendicular to the trench resulting from N-S extension. On the east side of the Mariana Ridge, thick sediment packages extend into the forearc. Directly east of Saipan and Tinian, a large, deeply scouring slide mass is imaged. Several serpentine mud volcanoes (Big Blue, Turquoise and Celestial) were imaged on the Mariana Forearc. Deep horizontal reflectors (likely original forearc crust) are imaged under the flanks of some of these seamounts. A possible "throat" reflector is resolved on multiple profiles at the summit of Big Blue, the northern-most seamount in the study area. The flanks of Turquoise seamount terminate in toe thrusts that represent uplift and rotation of surrounding sediments as the volcano grows outward. These thrusts form a basal ridge around the seamount similar to that previously noted encircling Conical Seamount. Furthermore, MCS data has revealed that some forearc highs previously thought to be fault blocks are in actuality mud volcanoes.
UR: http://www.soest.hawaii.edu/mariana