2021 Volume 21 Issue 4 Pages 4_49-4_64
The strong ground motion of the 1923 Kanto earthquake was recorded at Hongo, Tokyo by a Ewing disk-recording strong-motion seismograph. The seismograph consists of SW-NE, SE-NW and U-D components, and the original seismogram was traced on a tracing paper by Nasu (1957). The traced seismogram shows four sets of the traces which are lines of discontinuity due to scale-out of the indicator of the seismograph. Considering the different arm length curvatures in traces of the three components, the three component traces are distinguished from four sets of the traces. Although the distinguished traces have blank parts due to the scale-out of the indicator from the disk, the peak amplitudes of the SW-NE and SE-NW components are estimated to be about 20 cm and 40 cm, respectively.
