[SEM20-P03] Sensitivity of local electromagnetic response functions from Sq field to the electrical conductivity in the upper mantle
Here theoretical responses were evaluated at the depth of seafloor in order to apply the results on the electromagnetic field observed there. We first examine the sensitivity of the response functions for 1-d radially symmetric conductivity structure modified according to Olsen (1998). The responses for the Sq's principal modes are calculated using a method based on Banks (1969). In addition to showing the responses have sensitivity to 1-d structure, apparent resistivity calculated from Ex/By and Ey/Bx due to the principal modes are compared with those calculated assuming source field with spherical harmonic mode of n=1 and m=0 to discuss the influence of source field that has spatial structure. Then, we evaluate the influence of 3-d conductivity structure on the responses using forward modeling code by Uyeshima and Schultz (2000). Influence of land-sea conductivity contrast on the responses are shown. Also, sensitivity of the responses to a rectangular heterogeneous body (in a spherical coordinate) in the upper mantle is discussed by evaluating the responses by changing the size, depth, and conductivity of the heterogeneous body.
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