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Fig. 3. | Earth, Planets and Space

Fig. 3.

From: A normal-faulting seismic sequence triggered by the 2011 off the Pacific coast of Tohoku Earthquake: Wholesale stress regime changes in the upper plate

Fig. 3.

(a) Focal mechanisms of six earthquakes with magnitude greater than 1.5 that occurred before and after the 2011 Tohoku Earthquake. The origin time, magnitude and depth of each event are denoted above and below each beach ball. The distribution of polarities of P -waves is shown as circles (up) and crosses (down). Stations are plotted in lower hemisphere of focal sphere using the equal-area projection. These six events occurred at depths of 16.3 to 17.2 km, which are deeper than aligned hypocenters shown in Fig. 2(b). Gray circles are epicenters of relocated earthquakes in the present study. (b) Examples of 2–20 Hz filtered waveforms around the P-waves for two events, of which focal mechanisms are reverse (red waveforms) and normal faulting (blue waveforms). Each waveform is normalized by the maximum amplitude and aligned at the onset time of the P-wave.

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