Fig. 6

Slow earthquake activity in the Japan Trench before and after the 2011 Tohoku-Oki earthquake. a Epicenters of the slow earthquakes. b Spatiotemporal distribution of the slow earthquakes before the March 11, 2011, Tohoku-Oki earthquake. Potential ETSs before the Tohoku-Oki earthquake are numbered 1–6. c Spatiotemporal distribution of the slow earthquakes from January 2015 to December 2021. For an explanation of the symbols, refer to the legend in the figure. The epicenter of the Tohoku-Oki earthquake and its largest foreshock are from the JMA catalog. The coseismic slip (10 m or larger) and afterslip (April 23, 2011 to December 10, 2011) of the Tohoku-Oki earthquake are based on Iinuma et al. (2012) and Iinuma et al. (2016), respectively. The afterslip distribution is shown at 0.4 m intervals. The interplate locked region prior to the Tohoku-Oki earthquake is based on the slip deficit distribution estimated by Suwa et al. (2006) (larger than 6 cm/year, i.e., approximately 70% plate coupling). Tectonic tremors and VLFEs are from Nishikawa et al. (2019) and Baba et al. (2020), respectively. In the figure, we showed tectonic tremors with a duration of more than 80 s. Short-term SSEs are from Ito et al. (2013) and Nishimura (2021). The decade-long acceleration of aseismic slip prior to the Tohoku-Oki earthquake (10 cm or larger) is from Yokota and Koketsu (2015). The transient aseismic slip in early 2015 in the northern Japan Trench is based on Honsho et al. (2019)