Figure 1
From: Nucleation process of the 2011 northern Nagano earthquake from nearby seismic observations
Seismicity distribution in the study region. (a) Map view showing the MFT-detected earthquakes. Colored circles and diamonds denote MFT-detections. Size of circles scale with the corresponding events’ magnitude. Diamonds indicate small events for which was not possible to determine reliably magnitudes. Colors indicate lapse time from the Tohoku-oki megathrust event. The one-month relocated Hi-net aftershocks (M ≥ 1.0) are shown in gray. Pink star shows the March 12, 2011 Northern Nagano earthquake. The Moment Tensor focal mechanism of the M6.2 Nagano mainshock, determined by NIED, F-net broadband network is also shown. “West” and “East” indicate the two regions referred in the text. Black thick dashed line shows the profile AA’ in Fig. 2a. The black square and inverted green triangles represent the NZWH Hi-net borehole station and temporary surface stations, respectively. Rectangle with black thick solid line indicates the fault plane7 of M6.2 mainshock. The light dashed line shows prefecture border. (b,c) Time history of seismicity for the “West” and “East” clusters, respectively. Solid gray lines show the cumulative number of events for detections, respectively.
