Deep crustal seismic reflection profiling is carried out for first time across various tectonic domains of seismically active Mesozoic Kachchh rift basin, formed during the breakup of Gondwanaland. The seismic data, processed using the common reflection surface stack approach, provided maiden images of the shallow and deep sub-surface structures in the region. These images reveal a 15 km thick subhorizontal lower crustal reflection fabric and crustal-scale domal-type structure extending from the surface to the Moho. We interpret the earlier structure represent magmatic underplating and the latter as the Kachchh Mainland uplift. We find large variations in the thickness of sediments from 150 m to 6.5 km and crustal thickness from 45 to 35 km from north to south, with a Moho up warp of 4 km beneath the Kachchh Mainland fault. The Kachchh rift basin exhibits an unusually thick crust of 45 km, contrary to many rift basins. We interpret the syn-rifting and the Reunion mantle plume activity, manifested as Deccan volcanics, are responsible for magmatic underplating and crustal thickening. Uplift in the region is multi-genetic in origin. Present study illuminated new faults and nature of various other faults. Moderate to large earthquakes in the region are attributed to the regional and local stresses resulting from the plate boundary and heterogeneous crustal structure. Based on the mafic lower crust and distribution of aftershocks through the entire crust, we interpret the lower crust is brittle, contrary to most models of continental rheology.

中文翻译：

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印度西北部中生代卡奇裂谷的深地震反射成像：对进化的影响

首次对冈瓦纳大陆分裂期间形成的中生代卡奇裂谷盆地的地震活动活跃的各个构造域进行了深地壳地震反射剖面分析。使用常见的反射表面叠加方法处理的地震数据提供了该地区浅层和深层地下结构的首次图像。这些图像揭示了 15 公里厚的近水平下地壳反射结构和从地表延伸至莫霍面的地壳尺度圆顶型结构。我们将早期结构解释为岩浆底侵，将后者解释为卡奇大陆隆起。我们发现从北到南沉积物厚度从 150 m 到 6.5 km 不等，地壳厚度从 45 到 35 km 不等，卡奇大陆断层下方莫霍面向上扭曲 4 km。卡奇裂谷盆地的地壳厚达 45 公里，与许多裂谷盆地不同。我们解释了同裂谷和留尼旺地幔柱活动（表现为德干火山岩）是导致岩浆底侵和地壳增厚的原因。该地区的隆起具有多种成因。目前的研究阐明了新的断层和各种其他断层的性质。该地区的中到大地震是由板块边界和不均匀地壳结构产生的区域和局部应力造成的。根据镁铁质下地壳和余震在整个地壳中的分布，我们解释下地壳是脆性的，这与大多数大陆流变学模型相反。