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地壳尺度多次覆盖的近垂直深地震反射剖面产生大量的单边炮集,因浅层折射波的交互覆盖而产生众多的数据集。我们介绍一种推导浅层速度结构的方法,该方法是通过模拟和反演单边地震折射初至走时数据来实现的。我们将该方法应用于在印度地盾西北新元古代马尔瓦尔盆地进行的炮检距为100m、长12km的剖面上获得的数据集。该方法表明,在描述浅层折射层深度、陡的倾角和速度方面是成功的,即使缺少常规的相遇折射剖面也如此。研究揭示出马尔瓦尔盆地的2层沉积建造、默拉尼火山岩和复杂基底地形,并测量出了所估算模型参数的分辨率和不确定性。发现近道选排的地震截面图在性质上与导出的盆地结构特征相一致。在布格重力剖面上观测到的相对高和低的异常进一步证实了导出的这一速度模型。本文提出的方法对那些只能获得单边、多次覆盖的地震剖面数据集的近海等地区是非常有用的。
The near-vertical deep seismic reflection profiles with multiple crustal scales cover a large number of unilateral shotgun sets, resulting in numerous data sets due to the overlapping interaction of shallowly-refracted waves. We present a method for deriving shallow velocity structures by simulating and retrieving first-strike traveltime data from unilateral seismic refraction. We apply this method to a dataset obtained on a section 12 km long and offset at 100 m offset from the Neoproterozoic Marwar basin in the northwestern Indian Shield. The method shows that it is successful in describing the depth of shallow refraction layers, the steep dip angle and the velocity, even in the absence of a conventional encounter refractive profile. The study revealed two layers of sedimentary construction in the Marwar Basin, the Melaini volcanic rocks and complex basement topography, and the resolution and uncertainty of the estimated model parameters were measured. The seismic cross section of the near row selection was found to be qualitatively consistent with the derived basin structure. The relatively high and low anomalies observed on the Bouguer gravity profile further confirm this derived velocity model. The method proposed in this paper is very useful for offshore areas such as those that can only obtain unilateral and multiple seismic data sets.