| 講演要旨(和文) | | 海陸測線の場合,海上エアガン発震・陸上ダイナマイトおよびバイブレータ発震という震源タイプの違い,ならびに海上ハイドロフォン受振・陸上ジオフォン受振という受振器タイプの違いがある.本研究の目的は,海陸測線における相反定理を次に示すような3つのケースで理論的に実証することである.Case1:海エアガン→陸ジオフォンと陸バイブレータ→海ハイドロフォン.Case2:海エアガン→陸埋設ジオフォンアレイと陸ダイナマイト→海ハイドロフォン.Case3:Case2に対し陸ではリバースタイムリデイタミングを利用する.以上3ケースにおいて,それぞれ海上発震と陸上発震の記録を比較した.シミュレーション結果により三つの場合の全てにおいて到達時間と位相が一致することがわかった.またCase2, 3については振幅も一致する. |
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| | 講演要旨(英文) | | We used the finite-difference method to compute full wavefields to investigate combinations of source and receiver types and thus determine which combination is best for acquisition of transition-zone seismic data. First, we compared the synthetic time series recorded by an onshore geophone from an offshore airgun source with that recorded by an offshore hydrophone from an onshore vibrator source. Then, we compared the synthetic time series recorded by an onshore geophone from an offshore airgun source with that recorded by an offshore hydrophone from an onshore dynamite source. For both cases we found perfect agreement of the waveforms. For the onshore dynamite source, multicomponent geophones distributed in a wide array are needed to derive dilatancy. When onshore geophones are used at the surface, geometric symmetry is not obtained because the offshore streamer is towed a little below sea level and the dynamite source is fired a little below surface level. Accurate subsurface waveforms can be reconstructed from surface records by applying the reverse-time FD method. |
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