DataSheet1_Active faults studies in Delhi and national capital region (NCR): Inferences from satellite data and field investigations.docx

In recent years, the National Capital Region (NCR) of Delhi has experienced several earthquakes ranging in magnitude from 1.0 to 6.7. According to the last 50 years of earthquake data, the majority of earthquakes in the NCR have occurred near the Mahendragarh Dehradun Fault (MDF) and the Sohna Fault (SF). The region is bounded by a number of subsurface Ridges, Faults, and Lineaments, which are also influenced by the active plate boundary of the Indian and Eurasian plates. Active fault mapping is critical for the precise identification and marking of active fault traces in the NCR area for a precise seismic hazard assessment. We used high resolution Cartosat-1 stereopair data obtained from NRSC, Hyderabad, and Anaglyph (A 3D representation of the surface) and DEM prepared with ENVI software to map the active faults. We identified 12 sites in the NCR region based on satellite data interpretation, primarily along the MDF and Sohna Fault and their extensions. The presence of tectono-geomorphic markers along the MDF and Sohna Fault, such as warped surfaces indicative of fault scarps, stream offsets, gully erosion, and sag ponds, suggests active tectonic movement along these faults, most likely in the recent geological past. We believe the MDF is a right-lateral strike-slip fault with a compressional component on the western side and an extensional component on the eastern side. It acts as a segment boundary between compressional and extensional boundaries. We also identified the right lateral Nuh-Jhirka fault (NJF), which can be the Sohna Fault’s southern extension from Nuh to Jhirka. The western limb of the Delhi Mega fold has also seen a few right-lateral strike-slip movements that have extended up to the eastern bank of the Yamuna River, where the river reflects the base-level change and tight meandering on its upward side and a straight pattern on its downward side. This fault is known as the Delhi Fault (DF). The findings are preliminary, and further research would be required to create a detailed active fault map of the Delhi-NCR region to conduct a precise Seismic Hazard Assessment (SHA) of the region.

近年来，印度首都地区（NCR）德里经历了多次地震，震级范围从1.0至6.7不等。根据过去50年的地震数据，NCR地区的大多数地震发生在马亨德拉加尔-德里安断裂带（MDF）和索纳断裂带（SF）附近。该区域被众多地下脊、断裂和线性构造所环绕，这些构造亦受到印度和欧亚板块活跃板块边界的共同影响。精确的活断层制图对于NCR区域内活断层线的准确识别和标记，以进行精确的地震灾害评估至关重要。我们利用从海得拉巴的NRSC获得的高分辨率Cartosat-1立体对数据以及使用ENVI软件制备的伪彩色（地表的三维表示）和数字高程模型（DEM）来绘制活断层。基于卫星数据解释，我们在NCR区域内确定了12个地点，主要沿MDF、Sohna断裂带及其延伸部分。MDF和Sohna断裂带沿线的构造-地貌标志，如扭曲的表面表明的断层崖、河流错位、沟壑侵蚀和凹地，暗示了这些断裂带沿线的活跃构造运动，最有可能发生在最近的地质时期。我们认为MDF是一条具有西部压缩成分和东部伸展成分的右旋走滑断层，它是压缩和伸展边界之间的分段边界。我们还确定了右旋的努-吉尔卡断层（NJF），这可能是索纳断裂带从努到吉尔卡向南的延伸。德里大褶皱的西部支也经历了若干次右旋走滑运动，这些运动一直延伸到恒河的东岸，在那里河流反映了基面变化和上游的紧密弯曲以及下游的直线模式。该断层被称为德里断层（DF）。这些发现是初步的，进一步的研究将需要创建德里-NCR区域的详细活断层图，以进行该区域的精确地震灾害评估（SHA）。