Tidal sensitivity of shallow tectonic tremors in northeastern Japan

Shallow tectonic tremors along the northeastern Japan subduction zone show regional differences in their spatiotemporal evolution, raising the question of whether their response to tidal stressing also varies along strike. We analyze the tremor catalogue obtained by Sagae et al. (JGR, 2025, e2025JB031348)  for the period from August 2016 to August 2024. Based on their spatial distribution, tremor activity can be divided into three major regions: the southern end of the Kuril Trench (40.8–42°N; northern region), the northern Japan Trench (38.8–40.5°N; central region), and the southern Japan Trench (35–36.8°N; southern region). Here, we investigate the tidal sensitivity of tectonic tremors in these three regions. Our statistical analysis shows that tidal sensitivity is highest in the northern area, where tremors are clustered and occur in recurrent along-strike propagating bursts. Cluster-scale analyses in this northern region indicate that tidal sensitivity increases during the later stages of tremor clusters, consistent with the characteristics reported for deep tectonic tremors. Tidal sensitivity is intermediate in the southern area, where tremors appear more scattered. In the central region, where tremor activity has declined gradually since 2011 Mw 9.0 Tohoku-Oki earthquake, tidal sensitivity is lowest. In this region however, tremors and fast earthquakes occur in close spatial proximity. There, we further examine the relationship between tremor activity, fast earthquakes and tidal stress to explore potential interactions between slow and fast earthquakes.