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Progress in Earth and Planetary Science
Fig. 1 | Progress in Earth and Planetary Science

Fig. 1

From: Fault geometry of M6-class normal-faulting earthquakes in the outer trench slope of Japan Trench from ocean bottom seismograph observations

Fig. 1

Map of the survey area in the trench and outer trench slope of the central Japan Trench. a GCMT solutions (Dziewonski et al. 1981; Ekström et al. 2012) for Mw \(\ge\) 5.0 earthquakes from March 11, 2011, to December 2021. Only GCMT solutions located on the seaward side of the trench axis are plotted. The yellow shaded region is the coseismic slip area of the 2011 Tohoku-oki earthquake with 5-, 20-, and 50-m contours (Iinuma et al. 2012). The thick black dashed line indicates the Japan and Kuril trench axes. Thin dashed lines are the magnetic anomaly lineations (Nakanishi 2011). The dashed green line indicates the 3-month outer-trench aftershock area of the 1933 Showa-Sanriku earthquake (Uchida et al. 2016). b Close-up view of the survey area. OBS locations are indicated with black and white squares and inverted triangles for different observation periods. Focal mechanisms of three M6-class earthquakes in 2017 taken from the GCMT catalog (Dziewonski et al. 1981; Ekström et al. 2012) are indicated. White contours indicate 20-m and 50-m contours of the coseismic slip distribution of the 2011 Tohoku-oki earthquake (Iinuma et al. 2012)

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