利用地震噪声测量和钻孔数据估算安哥拉南部前卡拉哈里基底的深度

IF 2.2 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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引用次数: 0

摘要

安哥拉偏远的南部地区被卡拉哈里新生代硅质岩层所覆盖,这些岩层中蕴藏的地下蓄水层对受缺水问题影响的当地居民具有重要意义。在卡拉哈里砂达到适当厚度的地方,这些含水层发育良好。另一方面,在这一地区的东端,最近获得的区域航空磁力数据表明,位于赞比亚和刚果附近的卢菲利亚弧的地质结构有可能向西南延伸到安哥拉的卡拉哈里地层之下。一旦卢菲利亚弧与所谓的中非铜带的存在联系起来,这种可能性就会增加人们对确定卡拉哈里盆地下泛非洲岩石深度的兴趣。为了估算卡拉哈里地层在这一交通不便、物流不畅地区的厚度,需要一种快速、非侵入性的地球物理方法。选择了地震噪声和单站中村技术,但由于研究区域距离海洋(地震噪声的主要来源之一)较远,因此在 Cuvelai 地区进行了一次测试勘测,以评估信号质量,并利用现有钻孔对数据进行了校准。将结果与本工作中重新处理和验证的 1D 反演遗留垂直电测深结果进行了比较,显示出相似的基底深度,同时对地质构造的解释速度/密度进行了采样,并通过测量进行了确认。利用地震信息、机械探测和地质信息绘制了底层深度图。尽管覆盖的地理区域相对较小,但该地图为水文地质和矿产勘探提供了有价值的信息,并与之前可用的卡拉哈里厚度粗略地图以及地震勘测时同时进行的地质勘测观测结果相吻合。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Depth estimation of pre-Kalahari basement in Southern Angola using seismic noise measurements and drill-hole data

The remote Southern region of Angola is covered by siliciclastic Kalahari Cenozoic formations that host underground aquifers of great importance to local populations affected by water scarcity problems. These aquifers are well developed where Kalahari sands reach appropriate thicknesses. On the other hand, at the eastern end of this area, regional aeromagnetic data recently acquired suggested the possibility of the continuity of the geological structures of the Lufilian Arc, sited in the nearby Zambia and Congo, southwestwards into Angola under the Kalahari formations. Once the Lufilian Arc is associated with the presence of the so-called Central African Copperbelt, this possibility increased the interest in determining the depth to Pan-African rocks under the Kalahari basin. To estimate the thickness of Kalahari formations in this area of difficult access and poor logistics, an expedited and non-invasive geophysical method was needed. Seismic noise and the single-station Nakamura technique were chosen, but due to the large distance of the study area from the ocean, one of the major sources of seismic noise, a test survey was acquired in the Cuvelai region to assess the signal quality, where the data was calibrated using available drill-holes. >170 points of seismic ambient noise were later acquired and the horizontal/vertical (HVSR) amplitude versus frequency curves were 1D inverted for the best velocity/density model for each station. The results were compared with 1D inverted legacy vertical electrical soundings reprocessed and validated in this work, showing similar depth-to-basement, while interpreted velocities/densities of geological formations were sampled and confirmed with measurements. A depth-to-basement map was produced using seismic information, mechanical soundings, and geological information. Despite the relatively reduced geographical area covered, the map presents valuable information for hydrogeology and mineral exploration purposes and agrees with a previously available coarser map of Kalahari thickness and with observations from geological surveys simultaneously conducted at the time of the seismic surveys.

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来源期刊
Journal of Applied Geophysics
Journal of Applied Geophysics 地学-地球科学综合
CiteScore
3.60
自引率
10.00%
发文量
274
审稿时长
4 months
期刊介绍: The Journal of Applied Geophysics with its key objective of responding to pertinent and timely needs, places particular emphasis on methodological developments and innovative applications of geophysical techniques for addressing environmental, engineering, and hydrological problems. Related topical research in exploration geophysics and in soil and rock physics is also covered by the Journal of Applied Geophysics.
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