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Quantitative Constraints on Faulting and Fault Slip Rates in the Northern Main Ethiopian Rift
Tectonics ( IF 4.2 ) Pub Date : 2020-08-08 , DOI: 10.1029/2019tc006046
Melanie Siegburg 1 , Jonathan M. Bull 1 , Casey W. Nixon 2 , Derek Keir 1, 3 , Thomas M. Gernon 1 , Giacomo Corti 4 , Bekele Abebe 5 , David J. Sanderson 1 , Atalay Ayele 6
Affiliation  

The Boset magmatic segment (BMS) of the northern Main Ethiopian Rift (MER) is an ideal natural laboratory to investigate the kinematics, interaction, and rates of activity within a fault network in a magma‐rich rift. In this paper we take advantage of the availability of (1) high‐resolution remote sensing data (LiDAR, ASTER); (2) absolute age chronology on offset reference surfaces; and (3) well‐exposed active normal fault arrays to place new constraints on rift kinematics and strain distribution, and to quantify the architecture and fault slip rates at different temporal scales within a magmatic segment. We found that the rift border faults strike approximately NE, while the younger faults in the rift segments strike NNE. Analyses of geometric rift parameters show that the axial active part of the rift is transtensional with an increase of the shear component northward. The fault displacement analyses and displacement:length ratios increase toward the segment tips, suggesting a significant contribution of fault growth by linkage. In contrast, magmatism is focused on the segment center and localized to a narrow zone. Estimated fault slip rates vary, with rates of up to ~0.37 mm/year in ~0.3 Ma old rift floor deposits, whereas higher rates of up to ~4.4 mm/year are observed for faults cutting through ~6 Ka lavas. The difference in slip rates indicates short‐term variability or a very active recent episode compared to long‐term low average slip rates.

中文翻译:

北部埃塞俄比亚大裂谷断层和断层滑移率的定量约束

北部埃塞俄比亚大裂谷(MER)的Boset岩浆段(BMS)是理想的天然实验室,用于研究富含岩浆的裂隙中断层网络内的运动学,相互作用和活动速率。在本文中,我们利用(1)高分辨率遥感数据(LiDAR,ASTER)的可用性;(2)偏移基准面上的绝对年龄年表;(3)暴露良好的活动正断层阵列对裂谷运动学和应变分布施加了新的约束,并量化了岩浆段内不同时间尺度的构造和断层滑动率。我们发现裂谷边界断裂走向大约为NE,而裂谷段中较年轻的断裂走向为NNE。对裂谷几何参数的分析表明,随着向北剪切分量的增加,裂谷的轴向活动部分是张性的。断层位移分析和位移:长度比朝着段尖端增加,表明通过链接的断层增长的重大贡献。相反,岩浆作用集中在扇段中心,并局限于一个狭窄的区域。估计的断层滑动率各不相同,在约0.3 Ma的旧裂谷沉积物中,断层滑动率高达〜0.37 mm /年,而贯穿〜6 Ka熔岩的断层观测到的速率高达〜4.4 mm / year。与长期较低的平均滑差率相比,滑差率的差异表明短期变化或近期活动非常活跃。长度比率朝着段尖端的方向增加,这表明通过链接的断层增长的重要贡献。相反,岩浆作用集中在扇段中心,并局限于一个狭窄的区域。估计的断层滑移率各不相同,在〜0.3 Ma的旧裂谷沉积物中,断层滑动率高达〜0.37 mm /年,而贯穿〜6 Ka熔岩的断层观测到的速率高达〜4.4 mm / year。与长期较低的平均滑差率相比,滑差率的差异表明短期变化或近期活动非常活跃。长度比率朝着段尖端的方向增加,这表明通过链接的断层增长的重要贡献。相反,岩浆作用集中在扇段中心,并局限于一个狭窄的区域。估计的断层滑动率各不相同,在约0.3 Ma的旧裂谷沉积物中,断层滑动率高达〜0.37 mm /年,而贯穿〜6 Ka熔岩的断层观测到的速率高达〜4.4 mm / year。与长期较低的平均滑差率相比,滑差率的差异表明短期变化或近期活动非常活跃。每年大约有4毫米的断层穿过6个Ka熔岩。与长期较低的平均滑差率相比,滑差率的差异表明短期变化或近期活动非常活跃。每年大约有4毫米的断层穿过6个Ka熔岩。与长期较低的平均滑差率相比,滑差率的差异表明短期变化或近期活动非常活跃。
更新日期:2020-08-08
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