|
| | Abstract | | We newly developed a CSMT equipment to explore a concealed fault under a big city with a high amount of electromagnetic noise. The instrument realized high signal detection capability by synchronizing data sampling between the transmitter and receiver by using GPS. This equipment was applied to investigate the Uemachi fault, a concealed fault under Osaka city. The signal source was installed at Yamato-gawa. Receiving points were set up near Yodogawa Nagara-Bashi, which is about 15 km away from the signal source and to its north. The transmitted signal reached the receiving points was checked by conducting the frequency analysis of the received waveforms. The resistivity section across the Uemachi fault was obtained up to a depth of about 800m. The resistivity section is well correlated with the seismic reflection profile obtained in a previous study. It shows a high-resistivity zone inclining northeast in the region where the fault is presumed to be located. There is a high-resistivity region to the northeast of the fault. The former high-resistivity zone coincides with the flexure zone of the Uemachi fault. The latter zone coincides with the granitic rocks as the basement rock to the Osaka Group, indicating that the basement rocks in the northeast site of the fault are shallower than the southwest side. |
|
|
|
| |
|