Field Detection of Microcracks to Define the Nucleation Stage of Earthquake Occurrence

Figure 10

Coseismic electric field variation for the Tohoku earthquake (3.11) at Hasaki (lower sheet) and the strong motion seismograph (UD component) at nearest K-net observation site CHB005 (upper sheet, (1): EW, (2): NS, (3): UD). The vertical line “org”, “P”, and “S” are origin time of 3.11, P wave arrival time, and S wave arrival time at CHB, respectively. There is very faint electric phase corresponding P arrival time and none phase corresponding to S arrival. The first large negative peak coincides with the peak acceleration and the second prominent peak did not correspond to any phase.