A modified measurement method has been used to continuously observe earth potential difference (EPD) signals induced by seismic waves. This method reduces the level of extraneous signals induced by artificial and natural earth current sources. The observed signals were compared with the corresponding seismic waveforms from the Earthquake Observatory of Tohoku University, which is located 700 m from us. Comparison with each waveform component (acceleration, velocity, and displacement) showed that the proposed streaming potential model reflecting the earth acceleration adequately explains the EPD signal. The estimated ratio between the earth electrical field (potential difference) and the pressure difference in the ground, i.e., the coupling coefficient, was found to be reasonable based on the streaming potential model. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 52–59, 1998

A modified measurement method has been used to continuously observe earth potential difference (EPD) signals induced by seismic waves. This method reduces the level of extraneous signals induced by artificial and natural earth current sources. The observed signals were compared with the corresponding seismic waveforms from the Earthquake Observatory of Tohoku University, which is located 700 m from us. Comparison with each waveform component (acceleration, velocity, and displacement) showed that the proposed streaming potential model reflecting the earth acceleration adequately explains the EPD signal. The estimated ratio between the earth electrical field (potential difference) and the pressure difference in the ground, i.e., the coupling coefficient, was found to be reasonable based on the streaming potential model. © 1998 Scripta Technica, Electr Eng Jpn, 125(4): 5259, 1998

The composition areas of the A2/L21 two-phase field in the Fe-Al-Ti-Cr quaternary system at 800 ºC and 700 ºC were investigated using a diffusion-multiple (DM) technique for which Fe-30Al-7Ti, Fe-30Cr-7Ti and Fe-7Ti alloys were diffusion-coupled and heat-treated. The A2/L21 two-phase field was found to expand slightly toward lower Al content when the Cr content is increased. The field is slightly shifted toward lower Al content when the temperature is decreased.