10:00 AM - 10:15 AM
[SEM33-05] 3D Electrical Resistivity Imaging beneath Kyushu by Geomagnetic Transfer Functions and Network-MT Response Functions
A shallow depth resolution of the lithospheric-scale resistivity model, however, was too low to examine small-scale resistivity structures of the crust because of the period range between 480 and 40,960 s of the Network-MT data. Thus we have started to perform 3-D inversion analyses by using a data set of geomagnetic transfer functions whose period range is from 20 to 960 s to obtain a resistivity structure model, in which we can examine smaller-scale structures. The geomagnetic transfer functions were determined at 167 sites in the Kyushu district. Original raw data sets for the geomagnetic transfer functions were measured at the entire Kyushu island and several islands off the western coast of Kyushu from 1980,s to 1990,s [e.g., Handa et al., 1992; Shimoizumi et al., 1997; Munekane et al., 1997]. In this presentation, we will show a new electrical resistivity model, which is obtained through a two-stage inversion process as follows. We determine a resistivity structure mainly at a shallow depth by applying 3-D inversion analyses for the geomagnetic transfer functions of 20-960 s first and then determine a lithospheric-scale resistivity structure by applying 3-D inversion analyses for the Network-MT response functions of 480-40,960 s, which is based on values of the previous resistivity model determined by using the geomagnetic transfer functions. In the two-stage inversion process, we use two types of DASOCC inversion code [Siripunvaraporn et al., 2004; Uyeshima et al., 2008; Siripunvaraporn and Egbert, 2009].