The characteristics of BSRs and their derived heat flow on the profile 973 in the northeastern South China Sea
The characteristics of BSRs and their derived heat flow on the profile 973 in the northeastern South China Sea
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DOI：
10.1002/cjg2.1151
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发表时间：
2007-09
期刊：
影响因子：
--
通讯作者：
Song Hai-bin;Wu Shiguo;Jiang Wei-wei
中科院分区：
文献类型：
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作者：
Song Hai-bin;Wu Shiguo;Jiang Wei-wei
利用973工程对南海东北部新近获得的一条地震线进行处理，研究了衡春脊天然气水合物模拟底反射体的特征和分布。对不同类型地震剖面的分析表明，单通道地震剖面可以在一定程度上揭示该区bsr的分布，但要解决该区bsr的全面分布问题，地震资料处理起着重要作用。南海东北部的BSR具有世界大陆边缘BSR的典型特征：交叉沉积层反射，一般平行于海底，伴生反射具有强振幅和负极性。该区域bsr特征明显，表明南海东北部存在含天然气水合物的沉积。利用含混合气组成的甲烷水合物和天然气水合物相稳定边界曲线计算水合物稳定带底部深度，并与实测BSR深度进行对比。如果使用单一梯度地热曲线进行计算，则甲烷水合物或含有混合气体成分的天然气水合物稳定带的基底与沿整个地震剖面观测到的bsr深度不对应。因此，地温梯度沿剖面发生显著变化。利用BSR资料估算地温梯度和热流，计算结果表明，地温梯度和热流随离海沟距离的增加和离岛弧距离的减小而自西向东减小。计算得到的热流在28 ~ 64 mW/m(2)之间变化，与台湾西南近海实测热流基本一致。
Processing of a recently acquired seismic line in the northeastern South China Sea by Project 973 has been conducted to study the character and the distribution of gas hydrate Bottom-Simulating Reflectors (BSRs) in the Hengchun ridge. Analysis of different-type seismic profiles shows that the distribution of BSRs can be revealed to some extents by single-channel profile in this area, but seismic data processing plays an important role to resolve the full distribution of BSRs in this area. BSR' s in the northeastern South China Sea have the typical characteristics of BSRs on worldwide continental margins: they cross sediment bed reflections, they are generally parallel to the seafloor and the associated reflections have strong amplitude and a negative polarity. The characteristics of BSRs in this area are obvious and the BSRs indicate the occurrence of gas hydrate-bearing sediments in the northeastern South China Sea. The depth of the base of the gas-hydrate stability zone was calculated using the phase stability boundary curve of methane hydrate and gas hydrate with mixture gas composition and compared with the observed BSR depth. If a single gradient geothermal curve is used for the calculation, the base of the stability zone for methane hydrate or gas hydrate with a gas mixture composition does not correspond to the depth of the BSRs observed along the whole seismic profile. The geothermal gradient therefore changes significantly along the profile. The geothermal gradient and heat flow were estimated from the BSR data and the calculations show that the geothermal gradient and heat flow decrease from west to east, with the increase of the distance from the trench and the decrease of the distance to the island arc. The calculated 2 heat flow changes from 28 to 64 mW/m(2), which is basically consistent with the measured heat flow in southwestern offshore Taiwan.