炭山における小アレー地震観測

Abstract

Ground vibrational characteristics were studied with a small seismic arrayinstalled on sedimentary rocks of Tanba zone at Sumiyama, Kyoto. Spatialcorrelations were examined with coherency of the array data from local earthquakes, explosions and microtremors. Coherency appears to take a schematic form with twocutoff frequencies, fc and fs(fc<fs), as follows; (1) high flat level (coh2=1) in thelower frequency range below f, (2) rapid decrease with increasing frequency fromfc to fs and (3) low level with large fluctuation (coh2=0.5 - 0.8) in the higherfrequency range over fs fc and fs were estimated around 1 and 3 Hz, respectively, for the coherences between two sites separated by about 1 km. The characteristicsof coherency were discussed with interference of phases and wave scattering byheterogeneities of geographical and geological structures.