[S-SS10] Statistical seismology and underlying physical processes

[SSS10-03] Estimation of the epicenter of the 1894 Tokyo Earthquake using data of K-NET

*Tetsuo Hashimoto¹ (1.National Research Institute for Earth Science and Disaster Resilience)

Keywords:Tokyo Earthquake, K-NET, hypocenter

An earthquake occurred on June 20, 1894, which gave severe damages of many brick chimneys of houses and factories in Tokyo and 26 fatalities (Omori, 1899). Relatively recently Katsumata et al. (1999) and Furumura & Takeuchi (2007) researched estimating the hypocenter from seismic waveforms and strong ground motions. Here, we compared the strong-motion waveform record of the earthquake that occurred in the northern part of Tokyo Bay observed by K-NET and the record of the Tokyo Earthquake observed in Hongo (Katsumata et al., 1999). Fig. 1 (upper) shows candidates of the Tokyo Earthquakes that occurred in the northern part of Tokyo Bay such as earthquakes near the ground surface, earthquakes associated with the subduction of the Philippine Sea plate, earthquakes near the bottom of the Philippine Sea plate, and earthquakes associated with the subduction of the Pacific plate. Also Fig.1 is shown an epicenter of the Tokyo Earthquake from Utsu (1999). Since seismic records in Hongo are recorded in SE-NW and NE-SW components, the current seismometer records are converted into those components for comparison. In Fig.1 (lower), we show displacement waveforms of acceleration converted to displacement and their low-pass filtered waveforms at Sarue seismic station or Higashi-shirahige seismic station of K-NET. Amplitude of the low-pass filtered waveforms are displayed to be amplified for the original waveforms. The record in Hongo shows that the pulse waves with similar level are displayed in the SE and NE directions in the S wave and the initial motion is down (Katsumata et al., 1999). It is shown the similar waveforms of the M5.2 earthquake on September 12, 2015. The Tokyo Earthquake has been known low aftershock activity (Omori,1899). The aftershock activity of the 2015 earthquake is low. Also, the source depth is 56km consistent with the estimation of Takeuchi and Furumura (2007). The Tokyo Earthquake may be a similar hypocenter of the 2015 earthquake.