The specific fracture energy associated with large earthquakes was estimated to be much larger, by 5-6 of the order of magnitude, than that of the ordinary solid material in laboratory.
Waveform inversion technique was developed in an attempt to extract the information of detailed source rupture processes.
The numerical method to estimate the impulse response was developed and applied to laboratory data.
He invented the method for slip distribution on the fault plane by teleseismic waveform with Hiroo Kanamori.
In addition, he analysed significant earthquakes just after occurrence and distributed the results of analysis on the internet.