The Bilila-Mtakataka Fault (BMF), at the southern end of the western branch of the East African Rift System (EARS), has been used in various scaling relation studies and arguments about the strength of the lithosphere. We present evidence for a similar, though more degraded, frontal scarp on the graben-bounding synthetic Chirobwe-Ntcheu Fault (CNF), showing that this fault is active simultaneously with the BMF. We deployed 17 geophones for ∼60 days around the southern end of Lake Malawi, across the footwall and hangingwall of the BMF. Continuous microseismicity can be seen from the surface to ∼35 km depth highlighting a plane dipping ∼42°E. Lower-crustal earthquakes have previously been found in the EARS, and based on location and focal mechanism have been hypothesized to occur on planes that line up with the surface traces of large faults. However, no previous study of the EARS has revealed a fault plane throughout the crust that shows seismicity along its full length from the surface to the base of the crust. Rather, the lack of seismicity seen at mid-lower crustal depths, has led some people to the “jelly sandwich” hypothesis. Our results show that the entire crust is seismogenic, so support the “crème brûlée” model. In our two month deployment we recorded 22 aftershocks ML ≥ 2 from the March 8th, 2018 earthquake 200 km south of our array, 7 months after the mainshock, confirming that aftershock sequences in regions of low strain have a long duration, and could be the main component of seismicity in slowly straining regions.

中文翻译：

---

整个地壳都可能是地震发生的：来自马拉维南部的证据

位于东非裂谷系统 (EARS) 西部分支南端的比利拉-姆塔卡塔卡断层 (BMF) 已被用于各种尺度关系研究和关于岩石圈强度的争论。我们提供了在地堑边界合成 Chirobwe-Ntcheu 断层 (CNF) 上类似但退化程度更高的正面陡坡的证据，表明该断层与 BMF 同时活动。我们在马拉维湖的南端，穿过 BMF 的下盘和上盘部署了 17 个检波器，持续了大约 60 天。从地表到约 35 公里深度都可以看到连续的微地震，突出显示了倾斜约 42°E 的平面。以前在 EARS 中发现了下地壳地震，并且根据位置和震源机制假设发生在与大断层表面痕迹对齐的平面上。然而，以前对 EARS 的研究没有揭示整个地壳的断层平面，显示从地壳表面到底部的整个长度的地震活动。相反，中下地壳深度缺乏地震活动，导致一些人提出“果冻三明治”假说。我们的结果表明整个地壳都是地震发生的，因此支持“crème brûlée”模型。在我们两个月的部署中，我们记录了 22 次余震 M大号 从3月8日≥2，2018地震200我们的阵列，主震后7个月内，证实了在低应变区域余震序列公里，南有很长的时间，而且可能是地震活动的主要成分慢慢使劲地区。