本文選題：東沙群島西南海區(qū) + 海底地震儀(OBS)　； 參考：《熱帶海洋學(xué)報》2017年05期

【摘要】：為深入理解南海北部多道地震測線D80顯示的深反射信息,沿此測線布置OBS(15臺)地震測線(OBS2015-1),測線長300km,方向NNW—SSE,從水深800m陸坡延伸至3760m深海平原。文章利用Obstool軟件進行預(yù)處理(位置校正和時間校正等)、震相識別,利用FAST tomography軟件進行速度層析成像。速度結(jié)果表明,新生代沉積層速度1.6~3.5km·s-1,厚度約2km;中生界速度3.5~5.5km·s-1,平均厚度約3km。在洋陸過渡帶處,沉積基底受新生代巖漿活動影響,有較大起伏。在上陸坡處,上地殼存在向上凸起約5km的高速異常,在多道地震剖面中表現(xiàn)為雜亂反射的背斜構(gòu)造,上覆晚新生代地層也同步形變,推測可能是新生代晚期巖漿侵入造成。地殼厚度由陸坡的23~20km減薄至洋盆的8km。地殼下部存在7.0~7.6km·s-1的高速層,高速層由陸坡的5km左右逐漸遞減至海盆的2km左右,因上陸坡和洋陸過渡帶晚新生代巖漿活動活躍,作者認(rèn)為地殼下部高速層是由海底擴張停止后巖漿侵入形成。
[Abstract]:In order to deeply understand the deep reflection information shown by D80 seismic survey line D80 in the northern part of the South China Sea, OBS (15 stations) seismic line (OBS2015-1) is arranged along this line, which is 300km long and NNW-SSE-oriented, extending from 800 m deep slope to 3760 m deep sea plain. In this paper, we use Obstool software to pre-process (position correction and time correction, etc.), identify seismic phase, and use fast tomography software to perform velocity tomography. The velocity results show that the velocity of Cenozoic sedimentary layer 1.6~3.5km s-1 is about 2 km thick, and the Mesozoic velocity of 3.5~5.5km s-1 is about 3 km. In the transitional zone of oceanic land, the sedimentary basement is influenced by Cenozoic magmatic activity and has great fluctuation. At the upper slope, the upper crust has a high speed anomaly of about 5km uplift, which appears in multiple seismic profiles as a chaotic reflection anticline structure, and the late Cenozoic strata are also synchronized deformed, which may be caused by the late Cenozoic magmatic intrusion. The thickness of the crust is reduced from 23~20km in the continental slope to 8 km in the ocean basin. There is a high speed layer of 7.0~7.6km s-1 in the lower crust, and the high speed layer gradually decreases from the 5km of the continental slope to the 2km of the oceanic basin, because of the late Cenozoic magmatic activity in the upper continental slope and the transitional zone of the oceanic continent. The authors believe that the lower crust is formed by magmatic intrusion after the undersea expansion stops.
【作者單位】： 中國科學(xué)院邊緣海與大洋地質(zhì)重點實驗室(南海海洋研究所);中國科學(xué)院大學(xué);廣州海洋地質(zhì)調(diào)查局;
【基金】：國家自然科學(xué)基金項目(91328205,41376062) 海洋地質(zhì)保障工程項目(GZH20110205)~~
【分類號】：P736.1
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本文編號：2085306