Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data
Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data
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DOI：
10.1002/2016gc006700
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发表时间：
2017-03
期刊：
影响因子：
3.7
通讯作者：
Bedanta K. Goswami;K. Weitemeyer;S. Bünz;T. Minshull;G. Westbrook;S. Ker;M. Sinha
中科院分区：
文献类型：
--
作者：
Bedanta K. Goswami;K. Weitemeyer;S. Bünz;T. Minshull;G. Westbrook;S. Ker;M. Sinha
韦斯特内萨海岭标志着斯瓦尔巴群岛西部边缘已知的海底天然气水合物省的北部边界。洋脊东段的几个海底凹痕是活跃甲烷排放的场所。直到最近，地震反射数据还是对山脊下方进行成像的主要工具。 2011 年至 2013 年间，在山脊东南部采集了重合控制源电磁波 (CSEM)、高分辨率二维 (2-D) 气枪、扫描频率 SYSIF 和三维 (3-D) p 缆地震反射数据。CSEM 和地震数据包含横跨和沿山脊的剖面，穿过多个活动和非活动麻点。对 CSEM 和地震反射数据获得的电阻率模型的联合解释提供了有关麻点下方流体成分的新信息。麻点下方的山脊侧面和烟囱之间的天然气水合物稳定区（GHSZ）的横向阻力和地震反射特性存在相当大的变化。侧面的分层地震反射器与大约 300 Ωm2 的横向电阻相关，而烟囱内的地震反射器则表现出振幅消隐和混沌模式。烟囱内 GHSZ 的横向电阻在 400 至 1200 Ωm2 之间变化。从 3D p 电缆数据获得的方差属性还突出显示了断层和烟囱，这与电阻率异常相符。根据联合数据解释，山脊处可能存在广泛的天然气水合物，断层和烟囱内含有水合物和游离气体。然而，在活跃的烟囱处，气体的影响可能主导电阻异常。
The Vestnesa Ridge marks the northern boundary of a known submarine gas hydrate province in the west Svalbard margin. Several seafloor pockmarks at the eastern segment of the ridge are sites of active methane venting. Until recently, seismic reflection data were the main tool for imaging beneath the ridge. Coincident controlled source electromagnetic (CSEM), high‐resolution two‐dimensional (2‐D) airgun, sweep frequency SYSIF, and three‐dimensional (3‐D) p‐cable seismic reflection data were acquired at the south‐eastern part of the ridge between 2011 and 2013. The CSEM and seismic data contain profiles across and along the ridge, passing several active and inactive pockmarks. Joint interpretation of resistivity models obtained from CSEM and seismic reflection data provides new information regarding the fluid composition beneath the pockmarks. There is considerable variation in transverse resistance and seismic reflection characteristics of the gas hydrate stability zone (GHSZ) between the ridge flanks and chimneys beneath pockmarks. Layered seismic reflectors on the flanks are associated with around 300 Ωm2 transverse resistance, whereas the seismic reflectors within the chimneys exhibit amplitude blanking and chaotic patterns. The transverse resistance of the GHSZ within the chimneys vary between 400 and 1200 Ωm2. Variance attributes obtained from the 3‐D p‐cable data also highlight faults and chimneys, which coincide with the resistivity anomalies. Based on the joint data interpretation, widespread gas hydrate presence is likely at the ridge, with both hydrates and free gas contained within the faults and chimneys. However, at the active chimneys the effect of gas likely dominates the resistive anomalies.