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| | Abstract | | In Ikata, Ehime Prefecture in the west part of Shikoku Island, a seismic recording system in a deep borehole was deployed in December of 2012. Seismographs were installed at 2000m, 500m, 160m and 5m depth respectively, and have been recording ever since. We have estimated attenuation parameters in the deep borehole by using Q value inversion of data recorded during the Iyo-nada earthquake which occurred on March 14, 2014. The aim of this study is to further improve the fit of the transfer function result found previously [1], and examines ways to select the optimal solution from a large number of trials. As a result, we found that finely subdividing the attenuation structure depths close to the surface, (i.e. less than 300m) enabled a better transfer function fitting. Also, we tried to select an optimal solution from a large amount of inversions that is consistent with the transfer function data set corresponding to each trial. |
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