Analysis on Tilt and Settlement in Strong Motion Records

Abstract

Satoh (2020) pointed out that some velocity time histories by integrating acceleration records of vertical components have linear trends to the downward direction then become almost flat with values “Vnon” and interpreted that Vnon was caused by negative dilatancy. In this study from many strong motion records with large Vnon, we show that velocity time histories of the horizontal records have linear trends and estimate the tilt angles and directions of the ground using the linear trends. Several records with large Vnon have been pointed out the increase of excess pore water pressure. The tilt direction in the near-fault regions is almost radial and the tilt starts at S-wave potions. The estimated tilt angle is much larger than that by crustal deformation calculated from fault models. We interpret from these results and Satoh (2020) that the tilt motions are caused by nonlinear site responses including the increase and dissipation of excess pore water pressure or the negative dilatancy accompanied by the settlement of the ground.