Abstract:
Tomographic images of the subducting Pacific plate beneath the Izu-Bonin-Mariana arc illustrate a progression of geometries from shallow dipping to vertical from north to south along the arc. Recent advances in technology and inversion techniques have improved resolution of slab structure beneath the western Pacific island arcs, but reasons for the variation in geometry and morphology are still poorly understood. By comparing high-resolution tomographic images of the western Pacific and updated paleogeographic reconstructions, we are able to link the spatiotemporal evolution of the subducting Pacific plate back to the mid-Miocene. We have reconstructed tectonic motions along the Kurile-Japan-Izu-Bonin-Mariana arc system and the Ryukyu arc to provide an independent, additional interpretation of the subducting Pacific plate using the most current plate motion data. We then investigate the plausibility of our model and three other proposed models based on the interpreted slab structure from tomographic images. The new reconstruction agrees with the basic characteristics of former trench retreat models but illustrates the importance of the collision of the Ogasawara Plateau with the trench in the mid-Miocene and its subsequent effect on the slab structure at depth and the impact of other aseismic ridge collisions along the plate boundary. The combination of evidence in changed physical properties imaged with tomography and the current interpreted slab morphology can be analyzed with the past plate motions to understand subduction zone processes. Copyright 2006 by the American Geophysical Union.
