[SSS10-P14] Seismic Moments of Inland Small Earthquakes in Japan: Spectral Analyses Using the Hi-net
Keywords:seismic moment, Hi-net, small earthquakes
We calculated seismic moment for inland earthquakes shallower than 20 km deep with magnitudes from 3 to 4 occurred in 2013 to 2017. Firstly, we calculated a source spectrum from waveform data during 1s before to 9s after the S-wave arrival time. Then, correcting path, site, and the instrumental response, we estimated source spectra. Comparing the observed source spectra with a theoretical one supposing the ω2 model, we obtained the seismic moment.
The Hi-net detected 455 inland earthquakes with the magnitude from 3 to 4 in 2017. We successfully estimated the seismic moments more than 90 % of those earthquakes. We could estimate the moment magnitudes more than 90 % except 2016. Because the aftershocks of the Kumamoto earthquakes contaminated Hi-net records, we calculated the seismic moments only for 70 % of the 1730 earthquakes in 2016. We compared the moment magnitudes determined by the Hi-net with those by a moment tensor inversion of the F-net. The moment magnitude of Hi-net was smaller than those of the F-net by 0.13±0.11. On the other hand, the magnitude using the maximum amplitude of the Hi-net was larger than the F-net by 0.06±0.21.