HR: 0800h
AN: V51B-0539    [Abstracts]
TI: Improved Absolute Plate Motion Modeling in the Pacific
AU: * Wessel, P
EM: pwessel@hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1680 East-West Rd, Honolulu, HI 96822 United States
AU: Harada, Y
EM: harada@scc.u-tokai.ac.jp
AF: School of Marine Science and Technology, Tokai University, 3-20-1 Orido Shimizu, Shizuoka, 424-8610 Japan
AU: Kroenke, L W
EM: kroenke@soest.hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1680 East-West Rd, Honolulu, HI 96822 United States
AB: In studies of Relative Plate Motion (RPM), the model constraints are conjugate magnetic isochrons identified in marine magnetic anomalies. The model is a finite rotation that rotates an isochron on plate A such that the rotated segment matches the conjugate isochron on plate B. Chang (1987; 1988) solved for such rotations using nonlinear spherical regression and developed statistical confidence regions for the resulting rotations. Because conjugate data can be optimally superimposed using a single, finite rotation it was natural to define the model in terms of total reconstruction rotations. In studies of Absolute Plate Motion (APM), the constraints are the surface expressions of hotspot seamount chains and their measured ages. The traditional approach is to model coeval segments of seamount chains as small circles about stage poles of rotation found by minimizing the distances from each seamount to its locally best-fitting, small circle about a candidate pole. The opening angles are typically found by trial and error. Given the age range of a particular set of copolar segments, opening rates can be determined. Because the data portray small circles, it was natural to define the model in terms of stage rotations. The traditional APM modelling approach has many limitations, including (1) shorter segments, possibly reflecting APM changes, are difficult to identify and correlate across several chains; (2) short small-circle segments become indistinguishable from great circles and hence reliable poles cannot be determined; (3) without easily identifiable kinks between chain segments, ages are needed to make the correlation and these are often lacking; and (4) unlike RPM modelling, no rigorous approach for estimating APM uncertainties exists. However, Wessel and Kroenke (1997) developed a method to derive optimal hotspot locations from seamount data if the APM is known, whereas Harada and Hamano (2000) introduced a technique to determine total reconstruction rotations if hotspot locations are known. We improve the modelling of APM by combining these two complimentary methods into a self-consistent hybrid technique. The hybrid technique allows us to determine (1) the best location for hotspots, (2) a high-resolution APM model, and (3) covariance matrices for each rotation. We present the first self-consistent Pacific APM with confidence regions for each rotation pole and reconstructed points. The new model is contrasted with traditional models, and the implications of the model for drift within the Pacific hotspot group and the origin of the Hawaii-Emperor bend is addressed.
DE: 8194 Instruments and techniques
DE: 8155 Plate motions--general
DE: 8157 Plate motions--past (3040)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting