| 講演要旨(和文) | | 岩手県奥州市に位置する北上低地西縁断層帯南部の出店断層を研究対象として、堆積層及び基盤面の詳細構造,出店断層の形状と地震発生層下限までの深部延長,及び広域的な上部地殻構造の把握を目的とした深部地殻構造探査を実施した。併せて、地殻構造全体に関して自然地震観測を通じて制御震源データとの統合プロファイリングを試みた。また、三成分MEMS型加速度センサーを用いた長大展開による制御震源データ、並びに同センサーを用いた近地地震を中心とした連続自然地震データの取得を行い、制御震源から自然地震までの広帯域における信号抽出の可能性を検討した。 |
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| | 講演要旨(英文) | | The deep geometry of active faults and the mid-crustal detachment at the base of seismogenic layer is important for understanding active tectonic process and accessing the risk of destructive earthquakes. To investigate the deeper extension of active faults within the seismogenic layer, we conducted a seismic reflection profiling experiment across the western marginal faults of Kitakami lowland, northeast Japan. The combination of telemetry and independent recording system has provided the deployment of wide-angle survey line with dense seismic array. The simultaneous data acquisition of regional refraction, low-fold wide-angle reflection and dense reflection survey has been optimized by the integration of vibrator source focused on effective low-frequency bandwidth of sweep signal and the three-component digital accelerometers with broader frequency responses. The seismic reflection profile shows that the deeper extension of the western marginal faults of Kitakami lowland converges on the mid-crustal detachment. Along the reflection survey line, a dense seismic array with the combination of short-period seismometers and digital accelerometers was deployed for teleseismic and local-earthquake observation. We utilized multimode prestack migration for receiver function and interferometric seismic imaging for back scattered phases to investigate the lower crustal structure and Moho boundary. |
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