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| | Abstract | | We conducted a comparative field experiment in Jyoso City, Ibaraki Pref., Japan that is aimed to check the validity of CCA in comparison with SPAC and also to verify the possibility of applying CCA using simple moving coil seismometers. The results showed that in a limited frequency range CCA could provide a similar dispersion curve as that given by the SPAC method and also that using L22D seismometers, Sercel Inc. CCA could provide a similar result. The available frequency range, however, is limited higher than about 2.3 Hz not only in the cases using L22D of which the natural frequency is 2.0 Hz and the digital recorder GEODE, Geometrics Corp. that covers from 1.75Hz to 20 KHz, but also in the cases using VSE12-CC, Tokyo Sokushin Ltd. the feedback type seismometer that covers down to 0.05Hz and McSeis-MT, OYO Corp. the recorder that covers down to DC. This seems due to the resolution of A/D converters that are 24 bits but not enough to record the signals enough correctly to detect small phase difference of microtremor within the used small array in smaller frequency range. Besides, the recognition on the importance of the system characteristics correction is refreshed. |
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