Seismic Interpretation of Sill- 1 Complexes in Sedimentary Basins: The 2 ‘Sub-Sill Imaging Problem’
Seismic Interpretation of Sill- 1 Complexes in Sedimentary Basins: The 2 ‘Sub-Sill Imaging Problem’
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沉积盆地中 Sill- 1 杂岩体的地震解释：第二个“地下成像问题”
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
J. Howell
中科院分区：
文献类型：
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作者：
C. Eide;N. Schofield;I. Lecomte;S. Buckley;J. Howell
三维地震反射资料在沉积盆地火成岩系统中的应用，使人们对镁铁质地台杂岩的认识发生了一场革命。然而，地下22内的基床复合体的几何和结构如何与地震反射数据中成像的几何和结构相关联存在相当大的不确定性。为了提供如何解释地震数据中的地台复合体23的约束，我们给出了由东格陵兰24个地震尺度(22x0.25公里)露头生成的合成地震图，受丰富的野外数据约束。25这项研究强调了覆盖在火成岩上的火成岩如何降低地震幅度和频率，使27个陡峭的地貌几乎无法成像，从而对26个下伏侵入体和岩石的成像产生不利影响。此外，地震模拟表明，由于碎屑硅质岩和碎屑岩之间的高阻抗对比，原则上应该以相对较高的幅度成像29个薄(<；5m)侵入体。这与许多已发表的关于地震可检测性的“经验法则”背道而驰。31然而，实际地震数据结合测井数据显示有大量未成像的岩床侵入，这可能是由于分辨率有限、覆盖层复杂、33个速度模型差以及密集分布的岩床之间的干扰所致。通过更好地预测基床侵入的发生和几何形状，并将其包括在速度模型中，可以进行显著的改进34。
Application of 3D-seismic reflection-data to igneous systems in sedimentary basins has led to 20 a revolution in the understanding of mafic sill-complexes. However, there is considerable 21 uncertainty on how geometries and architecture of sill complexes within the subsurface 22 relates those imaged in seismic reflection-data. To provide constraints on how sill complexes 23 in seismic data should be interpreted, we present synthetic seismograms generated from a 24 seismic-scale (22x0.25 km) outcrop in East Greenland constrained by abundant field-data. 25 This study highlights how overlying igneous rocks adversely affect imaging of 26 underlying intrusions and rocks by decreasing seismic amplitude, frequency and making 27 steeply dipping features near-impossible to image. Furthermore, seismic modelling shows 28 that because of the high impedance contrast between siliciclastic host rock and dolerites, 29 thin (< 5m) intrusions should in principle be imaged at relatively high amplitudes. This is 30 contrary to many published ‘rules of thumb’ for seismic detectability of sill intrusions. 31 However, actual seismic data combined with well-data shows significant amounts of un- 32 imaged sill intrusions, and this is likely due to limited resolution, overburden complexity, 33 poor velocity-models, and interference between closely spaced sill-splays. Significant 34 improvements could be made by better predicting occurrence and geometry of sill intrusions 35 and including these in velocity models.