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| | Abstract | | Three-dimensional denisty and magnetic structures around the focal area of the 2008 Iwate-Miyagi Nairiku Earthquake was estimated using gravimetric and magnetic tomography. Analysis was done by the two steps as follows, 1. gravimetric inversion, 2. magnetic inversion introduced density constraint based on the Poisson relation. This analysis reveals that, 1. Ridge-like high denisty anomaly A extends in the north-south direction, which deepend as a col near the mainshock epicenter, 2.High magnetic anmalies are located at the north area around Mt. Yakeishi-dake and the south area,around Mt.Kurikoma, B, and low magnetic anomaly C extendes toward the west sorrounded by the high magnetic anomalies. Aftershock row extends across the high density anomaly A through the col. They ditribute closely in the low magnetic anomaly C but become sparse in the south high magnetic anomaly B. In contrast to such aftersock distribution, the epicenter distribution preceeding the 2008 earthquake ditributes in conformity to the density structure. In this study, I presented such relations between the crustal heterogeneity revealed from the tomography and the epicenter distribution. |
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