Bull. Fac. Agr., Saga Univ. Geo-electromagnetic surveys on three active faults (Minoh, Nishiyama and Sae Faults) in the Northern Kyushu Shun HANDA (Laboratory of Environmental Subsurface Science) Accepted August 31, 2011 Summary The geo-electromagnetic surveys are conducted on three active faults and fault system in the Northern Kyushu, Japan. In Minoh Fault system which seven faults consist of, the VLF-MT surveys along the lines across the fault indicate the low resistivity belts along five faults of the system. In Nishiyama Fault, the narrow low-resistivity belt with a wide of 2 m is found by the HFCSMT surveys at the densely distributed survey points, which receive the controlled radio sources in the frequency range of 1.2 khz to 150 khz. The DC, geomagnetic and VLF-MT surveys are applied in Sae Fault. The clear geomagnetic anomalies are found on the low-resistivity belt that is revealed by the DC and VLF-MT survey. The result of these surveys shows that the low-resistivity belts are found in almost all the active faults and the width of these belts is possibly a good indicator of the fault-activity. Key words: active fault, electromagnetic survey, low resistivity belt Handa and Sumitomo ELF-MT
VLFMT AG A BCDEF GAGAG VLF-MT Al fgrtspsc MT MT MT VLF-MT VLF-MT VLF-MT VLF-MT HFCSMT VLF-MT ABCDEF
Latitude Longitude G C C VLF-MT VL-kHz H-polarization S/N AG CC A
a b c d VLF-MT A a Ωm A
e f a-g g A VLF-MT B WNW B
B VLF-MT B b B b B B B B C ENE CCCCC VLF-MT ELF-MT CB c C B C A C D DD D D D DD D DD
E E E E VLF-MT e F F f F G G Ωm D A
HFCSMT VLF-MT L M F F HFCSMT ABCD B VLF-MT HFCSMT VLF-MT B HFCSMT F F HM L
khz HFCSMT B AC D A aa ABC CD A D S/N khz F F F B D ABCD F kkhz
khz HFCSMT F khz Ωm F A F F B CD AB D CD C B VLF-MT HFCSMT VLF-MT khz khz VLF -MT S.D. VLF-MT HFCSMT
B HFCSMTkHz) VLF-MTkHz) SD. FSF HFCSMT VLF HFCSMT FS HFCSMT VLF -MT HFCSMT B F HFCSMT VLF-MT VLF-MT
VLF-MT ABC A C A AA VLF- MT an na VLF-MT
VLF-MT Ωm. Layer sno. DCV DCV Resistivity Thickness Resistivity Thickness ABC ABC VLF-MT A Ωm A DCV a Ωm DCVΩm DCVΩm DCV Ωm DCVΩm
ABC ABC nt S.D. B C B A nt AB C AC C λ
AC hdl κ AC hd LC A h κt κ T nt κ AC d VLF-MT FF BB VLF-MT FF VLF-MT
FF VLF-MT FF VLF-MT HFCSMT VLF-MTHFCSMT
VLF-MT HFCSMT HFCSMT VLF -MT VLF-MT HFCSMT VLFMT HFCSMT Electromagnetic Research Group for the Active Fault (1982). Low electrical resistivity along an active fault, the Yamasaki fault. J. Geomag. Geoelectr.:34, 103-127. Handa S. and N. Sumitomo (1985). The geoelectric structure of the Yamasaki and Hanaori faults, Southwest Japan. J. Geomag. Geoelectr.:37, 93-106. No VLF-MT
No http://www.jishin.go.jp/main/chousa/04 dec _nishiyama/index.htm. CSMT CSMT No Grant F. S. and G. F. West (1965). Interpretation theory in applied geophysics. McGraw-Hill Book Co., p.319-324.