Chapters authored
Tectonic Basin Formation in and Around Lake Biwa, Central Japan
Part of the book: Mechanism of Sedimentary Basin Formation
Post-Opening Deformation History of the Japan Sea Back-Arc Basin: Tectonic Processes on an Active Margin Governed by the Mode of Plate Convergence
Three-dimensional structure of the Japan Sea back-arc basin is investigated based on an extensive reflection seismic survey. The process of the Oligocene to early Miocene rifting is described in reference to a geologic database, and the most likely paleoreconstruction of rifted continental fragments is presented. The back-arc region has been subjected to intermittent post-opening deformation events, which the author regards as side effects of temporal shifts in the convergence mode of the Philippine Sea Plate (PSP). The southern shelf of the Japan Sea appears to have suffered North-South strong contraction for a short period of time during the latest Miocene. Resumed convergence of the PSP was responsible for the regional tectonic event because frequent igneous intrusions within the upper Miocene series upon the back-arc shelf, which was confirmed by a borehole stratigraphic study, are suggestive of revitalized arc volcanism linked to dehydration of the subducted slab. During the Quaternary period, confined structure in varied forms developed on the shelf, which is related to the dextral wrench deformation of southwest Japan and the eventual arc-parallel crustal breakup along the back-arc region. Simultaneous highly oblique subduction of the PSP provoked the prevailing shear stress and conspicuous neotectonic deformation.
Part of the book: Tectonics
Time-Series Analysis of Crustal Deformation on Longstanding Transcurrent Fault: Structural Diversity along Median Tectonic Line, Southwest Japan, and Tectonic Implications
The Median Tectonic Line (MTL) along the longstanding convergent margin of eastern Eurasia has been activated intermittently since ca. 100 Ma. In its incipient phase, propagating strike slips on the MTL generated an elongate pull-apart depression buried by voluminous clastics of the Late Cretaceous Izumi Group. In this study, the complicated deformation processes around this regional arc-bisecting fault are unraveled through a series of quantitative analyses. Our geological survey of the Izumi Group was exclusively conducted in an area of diverse fault morphology, such as jogs and steps. The phase stripping method was introduced to elucidate the time sequence of cumulative tectonic events. After stripping away the initial structure related to basin formation, neotectonic signatures were successfully categorized into discrete clusters originating from progressive wrenching near the active MTL fault system, which has been reactivated by the Quaternary oblique subduction of the Philippine Sea Plate. The method presented here is simple and effective for the detection and evaluation of active crustal failures in mobile belts where records of multiphase architectural buildup coexist.
Part of the book: Earth’s Crust and Its Evolution