| 講演要旨(和文) | | 警固断層系のほぼ中央部で,地表兆候が認められていない那珂川低地の地下構造を調べるために,福岡市の那珂川沿いの道路で2005年に実施した反射法地震探査調査データの再処理を行った.以下の2点の処理の変化により,波形のまとまりがよくなり,加野ほか(2006)と比べ連続性のよい反射面を得ることができた.第1に周波数帯域をS波では5-60Hz,P波では40-600Hzと広げたこと,第2に発震点ギャザ・受振点ギャザにF-Xデコンを適用し,交通ノイズや風のノイズなど震源に起因しないようなノイズを抑制し,これにより初動部分のS/Nを向上させてから走時を読み取り,静補正の精度を向上させたことである.P波の深度断面図とS波の深度断面図の対応はかなりよいものとなった.これまで警固断層が想定されていた地表位置の周辺の地下に反射面の約15mの深度変化が認められた.またいくつかの断層と思われる変形が認められた. |
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| | 講演要旨(英文) | | I reprocessed the Nakagawa line data, the very shallow seismic reflection surveys conducted in November 2005. The surveys were conducted across the southeastern part of the Kego fault along the Nakagawa river using both P-wave, a drop-hitter, and S-wave, plank striking by a wooden sledgehammer. In both surveys we used a 48-channel landstreamer system. The source and receiver spacing is 1m, except for the some part of P-wave survey, where the source spacing is 2m. Frequency ranges of the lower limit for reprocessing are lowered compared with the previous processing and the ranges are 5-60Hz for S-wave and 40-600Hz for P-wave. By aplying F-X deconvolution, the first break of P-wawe became easy to pick. This resulted in better statics. Mainly by these things, the reflection events continuity was inproved. In the northern part of the survey line the strong event exists at about 20-30m in depth. It decreases the depth in the middle of the line from CMP no. 1100 through 1200 to near the surface with about 15m difference. This suggests that Kego fault may crosscut this part of the survey line. Other faults are interpreted checking the both P and S-wave depth sections. |
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