Oceanic crust and Moho of the Pacific Plate in the eastern Ogasawara Plateau region
Oceanic crust and Moho of the Pacific Plate in the eastern Ogasawara Plateau region
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DOI：
10.1111/j.1440-1738.2007.00589.x
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发表时间：
2007-09
期刊：
影响因子：
1.5
通讯作者：
T. Tsuji;Y. Nakamura;H. Tokuyama;M. Coffin;K. Koda
中科院分区：
文献类型：
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作者：
T. Tsuji;Y. Nakamura;H. Tokuyama;M. Coffin;K. Koda
摘要为了显示小笠原高原东部海洋地壳和莫霍面的结构，我们分析了工业标准的二维多道地震反射数据。为了获得改进的速度模型，利用地震信号的相位信息进行速度分析，确定了莫霍面以上洋壳的速度模型。我们将这种速度分析技术应用于小笠原高原东部周围的地震反射数据，得到了清晰的洋壳和莫霍面内部结构图像。在小笠原高原以南，莫霍面在高原附近加深。远离高原的莫霍面在海底以下约7 km，而靠近高原的莫霍面在海底以下约10 km。高原南北洋壳和莫霍面特征差异明显。在北部，洋壳结构不明确，海底较浅，不太光滑，莫霍面不连续。在南部，洋壳和莫霍面内的结构成像清晰，海底较深。高原南部强烈的莫霍面反射可能代表层状辉长岩和橄榄岩之间的尖锐边界。然而，不连续的莫霍面反射高原北部可能代表粗糙的地形，因为强烈的岩浆活动或在一个厚的莫霍面过渡带内的速度逐渐向下增加。高原北部的断裂带也将不同性质的洋壳和莫霍面分隔开来，表明高原与断裂带之间岩浆活动强烈，小笠原高原和断裂带影响了洋壳和上地幔的成因。在地震属性显示的剖面图中，高原北部和南部的声学特征明显不同。
Abstract To show the structure of oceanic crust and Moho around the eastern Ogasawara Plateau, we have analyzed industry‐standard two‐dimensional multichannel seismic reflection data. To obtain improved velocity models, phase information of seismic signals was used for velocity analysis and velocity models for oceanic crust above Moho were determined. We apply this velocity analysis technique to seismic reflection data around the eastern Ogasawara Plateau, with the result of clear images of structures within oceanic crust and Moho. South of the Ogasawara Plateau, Moho deepens proximal to the Plateau. Moho distal to the Plateau is ca 7 km below sea floor (bsf), whereas it is ca 10 km bsf near the Plateau. The characters of oceanic crust and Moho differ significantly north and south of the Plateau. To the north, the structure of oceanic crust is ambiguous, the sea floor is shallower and less smooth, and Moho is discontinuous. To the south, structures within oceanic crust and Moho are imaged clearly, and the sea floor is deeper. A strong Moho reflection south of the Plateau might represent a sharp boundary between layered gabbro and peridotite. However, discontinuous Moho reflections north of the Plateau might represent rough topography because of intensive magmatism or a gradual downward increase in velocity within a thick Moho transition zone. A fracture zone north of the Plateau also appears to separate oceanic crust and Moho of different characters, suggesting vigorous magmatism between the Plateau and the fracture zone, and that the Ogasawara Plateau and the fracture zone influenced the genesis of oceanic crust and upper mantle. Differences in acoustic characteristics to the north and south of the Plateau are apparent in profiles illuminated by seismic attributes.