Ikuei Muramatu

Seismic moment of the 1891 Nobi, Japan, earthquake estimated from historical seismograms

The seismic moment of the 1891 Nobi, Japan, earthquake has been evaluated from the historical seismogram recorded at the Central Meteorological Observatory in Tokyo. For this purpose, synthetic seismograms from point and finite source models with various fault parameters have been calculated by a discrete wave-number method, incorporating the instrumental response of the Gray-Milne-Ewing seismograph, and then compared with the original records. Our estimate of the seismic moment (Mo) is 1.8×1020 N m corresponding to a moment magnitude (Mw) 7.5. This is significantly smaller than the previous estimates from the distribution of damage, but is consistent with that inferred from geological field survey (Matsuda, 1974) of the surface faults.