| 講演要旨(和文) | | 重磁力トモグラフィの手法を用いて,2008年岩手・宮城内陸地震震源域の三次元密度・磁気構造を推定した.解析は,1)重力異常の逆解析,2)密度構造をPoisson relationを介して拘束条件と与えた磁気異常の逆解析,の2段階で行った.これより,1)尾根状の高密度域Aがほぼ南北に延びるが,本震震源付近で鞍部状に深くなっている,2)北の焼石岳付近,南の栗駒山以南に高磁化強度域Bがあり,1)の鞍部に相当する位置で低磁化強度域Cが西方に入り込んでいる(取り残されている),といった特徴が認められた.余震分布は,高密度域の鞍部を通り高密度域Aを切って分布している.また,低磁化強度域C内にでは密集しているが,南東の高磁化強度域B内ではばらけている.なお,今回の地震までの震源分布は,密度構造に調和的に分布している.ここでは,このような物性不均質性と震源分布との関係について報告した. |
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| | 講演要旨(英文) | | 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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