Kebede Bisrat, Mammo Tilahun
School of Earth Science, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.
Ministry of Mines and Petroleum, P.O. Box 486, Addis Ababa, Ethiopia.
Heliyon. 2021 Apr 24;7(4):e06872. doi: 10.1016/j.heliyon.2021.e06872. eCollection 2021 Apr.
The study area is situated in the Southern Main Ethiopian Rift being bounded within the limit of 3700″0'-3850'00″E and 550'00″-700'00″N. It is well known that the complex geological structure of the Main Ethiopian Rift has attracted intense attention so far and numerous geophysical investigations have been performed using potential field data-sets in Central and Northern Main Ethiopian Rift with the exception of the Southern Main Ethiopian Rift which is poorly constrained. Analysis of Full Tensor Gravity anomalies helps in understanding of the nature of shallow subsurface structural features and has a paramount importance in building general understanding of subtle details about subsurface geology of the area. Separation of regional and residual gravity field is performed using upward continuation filtering technique. The residual gravity anomaly caused by local structures and anomalous body delineated four sub-basins with low amplitude response which is in agreement with the vertical gravity gradient anomaly (G) and tilt derivative horizontal (TDX) that clearly outlined and characterize edges of the sub-basins. The sub-basins delineated are the northern and southern Abaya, Chamo and Gelana basins. The tilt angle method which is used to delineate major subsurface structures and determine the source depth results showed that the area was affected by different lineament trending NE-SW, N-S, NNE-SSW, NW-SE and E-W, directional analysis performed indicates that the dominant trend is in agreement with the regional fault orientations. The estimated depth to the top of the lineaments on average varies from 0.9 km to 3.1 km and it is relatively deeper in the basins compared to the surrounding areas giving clues to the amount of sediment infill.
研究区域位于埃塞俄比亚主裂谷南部，范围在东经37°00′ - 38°50′00″和北纬5°50′00″ - 7°00′00″之间。众所周知，埃塞俄比亚主裂谷复杂的地质结构至今已吸引了广泛关注，人们利用位场数据集在埃塞俄比亚主裂谷中部和北部进行了大量地球物理调查，但埃塞俄比亚主裂谷南部的情况则约束较少。全张量重力异常分析有助于了解浅层地下构造特征的性质，对于全面了解该区域地下地质的细微细节至关重要。利用向上延拓滤波技术分离区域重力场和剩余重力场。由局部构造和异常体引起的剩余重力异常圈定了四个具有低幅度响应的子盆地，这与垂直重力梯度异常（G）和倾斜导数水平分量（TDX）一致，它们清晰地勾勒出子盆地的边缘并对其进行了特征描述。圈定的子盆地为北阿巴亚、南阿巴亚、查莫和盖拉纳盆地。用于圈定主要地下构造并确定源深度的倾斜角方法结果表明，该区域受到不同走向的线性构造影响，走向为东北 - 西南、南北、北北东 - 南南西、西北 - 东南和东西向，方向分析表明主导走向与区域断层方向一致。估计线性构造顶部的平均深度在0.9公里至3.1公里之间，与周边地区相比，盆地中的深度相对更深，这为沉积物填充量提供了线索。
