Abstract

Integrated geophysical surveys, comprising marine magnetic, high resolution shallow seismic and single-beam bathymetry were conducted to assess subsurface tectonics of the Mid-Thane Creek (MTC) of Mumbai. The bathymetry in the intertidal zone of MTC varies drastically due to periodic dredging, with maximum depth up to 6.4 m and a minimum of ~−1.6 m. High resolution shallow seismic sections up to the depth of ~35 m from the sea-floor are generated to analyze the neotectonic activity of the creek. Imprints of deep-seated lineaments are recognized from magnetic anomaly map of the MTC. To delimit lateral extent of the lineaments/faults, results of several derivative methods including tilt derivative and standard Euler deconvolution are merged with the selected crest value of the horizontal derivative. To estimate depth to the source, Euler deconvolution, tilt derivative, analytic signal, and source parameter imaging method have been used. However, the depth estimation for the lineaments/faults is highly discrepant for this region, because of the complex tectonics associated with the periodic emplacements of Deccan flood basalt. To confine the top and bottom boundary of this highly magnetized basaltic layer, we have carried out spectral analysis considering 18 windows of 2000 × 2000 m with an overlap of 500 m. The average depth to the top and bottom of the source body estimated using spectral analysis is consistent with the depth estimated from the derivative filters. This confirms that the lineaments identified by the derivative filters may embed in the basaltic layer of MTC. The most prominent lineament interpreted from the seismic and magnetic data, in the central region of MTC is inferred as the marine analogue of Alibagh–Uran Fault passing through the mainland of Alibagh and Uran close to Mumbai city.

Highlights

• Acquired, processed and interpreted high resolution shallow seismic, marine magnetic, single beam bathymetry data in the Mid-Thane creek of Mumbai, India.

• Neo-tectonic and deep-seated tectonic elements are identified using the seismic and magnetic data.

• Identification of the faults/lineaments and source depth estimation are performed using total horizontal, analytic signal, tilt derivative, Euler deconvolution and source parameter imaging derivative methods.

• Thickness of the flood basalt where the faults/lineaments are embedded is estimated using spectral analysis.

• Interpreting the marine extension of Alibagh–Uran fault zone in the Mid-Thane creek of Mumbai, India.

中文翻译：

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印度孟买中塔那河的构造评价：一种综合的地球物理方法

摘要

进行了包括海洋磁，高分辨率浅地震和单波束测深仪在内的综合地球物理勘测，以评估孟买中塔那河（MTC）的地下构造。由于定期挖泥，MTC潮间带的测深法发生了巨大变化，最大深度达6.4 m，最小约〜1.6 m。生成了距海底约35 m深度的高分辨率浅层地震剖面，以分析小河的新构造活动。从MTC的磁异常图可以识别出深层的纹痕。为了确定线条/断层的横向范围，将包括倾斜导数和标准欧拉反卷积在内的几种导数方法的结果与所选的水平导数波峰值合并。要估算到源的深度，已经使用了欧拉反卷积，倾斜导数，分析信号和源参数成像方法。但是，由于与Deccan洪水玄武岩的周期性位移有关的复杂构造，该地区的构造/断层深度估计存在很大差异。为了限制此高度磁化的玄武岩层的顶部和底部边界，我们考虑了18个2000×2000 m重叠500 m的窗口进行了光谱分析。使用频谱分析估计的源体顶部和底部的平均深度与从导数滤波器估计的深度一致。这证实了由导数过滤器识别的线条可能会嵌入MTC的玄武层中。从地震和磁学数据得出的最突出的特征，

强调

• 在印度孟买中塔那河中获取，处理和解释的高分辨率浅层地震，海洋磁，单波束测深数据。

• 利用地震和磁性数据识别新构造和深层构造要素。

• 使用总水平，分析信号，倾斜导数，Euler反卷积和源参数成像导数方法进行断层/沿线的识别和源深度估计。

• 嵌入断层/构造的玄武岩的厚度可以通过频谱分析来估算。

• 解释印度孟买中塔那河中阿里巴格-乌兰断层带的海洋延伸。