The Mahelma fault, located upon the Sahel anticline at the tip of the major Sahel fault, is often suspected to be a secondary structure. Yet, to date, the Mahelma fault has displayed no definitive evidences for faulting activity and no unambiguous typology. This paper reviews new data, especially geological and subsurface data, acquired through the Algiers west microzoning project. The data indicate that (1) the Mahelma fault is an antithetic high-angle reverse fault, (2) the interpreted dip is around 80° toward the SSE and thus implies a North-verging fault, and (3) the fault zone has been observed in several fault sites and allowed direct observation of fault displacements and fault throws. (4) Displacements directly related to the Mahelma fault affect clearly young sediments including consolidated Quaternary sands. We suggest that the Mahelma fault forms an active backthrust originating from pre-existing normal fault with a possible linkage and interaction with the major Sahel forethrust. We conclude from the foregoing that the Mahelma fault most likely ruptures in concert with earthquakes on the Sahel main fault. The results also point the activity of the Sahel fault-related fold and hence complicate earthquake hazard analyses.

中文翻译：

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Mahelma断层：Sahel背斜的次级构造？

Mahelma断层位于主要Sahel断层末端的Sahel背斜线上，通常被怀疑是次级构造。然而，迄今为止，马赫尔玛断层没有显示出断层活动的确切证据，也没有明确的类型学。本文回顾了通过阿尔及尔西微区划项目获得的新数据，尤其是地质和地下数据。数据表明：（1）Mahelma断层是对角高角度反向断层；（2）解释的倾角向SSE倾斜约80°，因此意味着北向断层；（3）断层带为在几个断层现场观察，并可以直接观察断层位移和断层投掷。（4）与Mahelma断层直接相关的位移明显影响年轻的沉积物，包括固结的第四纪砂岩。我们建议，Mahelma断层形成一个主动反冲，其起源于既有的正常断层，并可能与萨赫勒大前推力发生联系和相互作用。从前面的结论我们可以得出结论，马赫尔玛断裂很可能与萨赫勒主断裂的地震一起破裂。结果还指出了萨赫勒断裂带相关褶皱的活动，因此使地震危险性分析复杂化。