福島県いわき市沖の下部更新統磐城海底地すべり堆積体（Iwaki SLS）に認められるポップアップ構造の形態的・堆積学的な特徴と形成過程

抄録

The internal and external morphometric characteristics were described and formation process was discussed for the Iwaki submarine landslide（Iwaki SLS）, which was discovered at the sub-bottom of the continental shelf off Iwaki City, Fukushima Prefecture, Japan, by three-dimensional（3D）seismic interpretation.

In this study area, the Lower Pleistocene was subdivided into nine layers based on the observation of seismic facies and seismic stratigraphic characteristics. Layers 1b to 4 were involved in the Iwaki submarine landslide, and twenty pop-up blocks and nine pop-up walls were formed in association with a group of conjugated reverse faults. The pop-up blocks, which were displaced upward with less deformation and remained almost as internal sedimentary structures, are interpreted to collapse at their fringe and eroded at the crest concurrently with pop-up displacement, supplying debris around the blocks.

The pop-up walls are arranged in nine lines warped arcuately in the downstream direction. All arrays of pop-up walls terminate at the northeast end against a linear side escarpment, and are in direct contact with un-moved sediments of the same horizon in the northeast area. The side escarpment at the southwest side is interpreted as strike-slip echelon faults.

The pop-up sequence was not revealed by the available dataset; however, circumstantial evidence suggests that sliding and pop-up movement in the Iwaki SLS occurred within a relatively short period of time.