Fig. 1
From: Crustal structure beneath earthquake swarm in the Noto peninsula, Japan
a Map showing the study area. While stars denote the epicenters of the 1993 Noto-Hanto-oki and 2007 Noto-Hanto earthquakes. The F-net focal mechanism solution is shown for the 2007 event. Orange circles represent locations of two sites with 3He/4He ratios of > 2.0Ra (Umeda et al., 2009), and red triangles denote active volcanoes. The location of the area is shown in the inset map by a rectangle. b Magnitude–time plots (black) and cumulative number (red) of the Noto earthquake swarm (M ≥ 1) shown in c. c An enlarged map of the Noto earthquake swarm. Colored dots denote earthquakes (M ≥ 1) that occurred from January 2003 to March 2022. Epicenters of three M ≥ 5 earthquakes (M5.1 on September 16, 2021, M5.4 on June 19, 2022, and M5.2 on June 20, 2022) are shown by white stars with the F-net focal mechanism solutions. d A frequency–magnitude distribution for earthquakes shown in c