CHARACTERISTIC OF THE INTRA-SLAB EARTHQUAKE AND SLOPE FAILURES RELATED TO THE 2021 FUKUSHIMA OFFSHORE EARTHQUAKE

Abstract

 An intra-slab earthquake with a magnitude of 7.3 that struck in off the coast of Fukushima on February 13, 2021 caused damage to slopes and houses. This article investigates the generation mechanism of this earthquake and the damage to the slopes based on the strong motion data recorded by the National Research Institute for Earth Science and Disaster Resilience (NIED) and the dataset from previous studies. Analyses of the data indicated that the peak ground acceleration of the earthquake showed larger value than the interplate earthquakes. In addition, microscopic observation and energy dispersive X-ray analysis of samples from the collapsed road slope near Matsukawaura bridge revealed that microorganism such as diatoms and green algae might induce the rock collapse.