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Determining Histories of Slip on Normal Faults With Bedrock Scarps Using Cosmogenic Nuclide Exposure Data
Tectonics ( IF 3.3 ) Pub Date : 2021-01-16 , DOI: 10.1029/2020tc006457
H. J. Goodall 1 , L. C. Gregory 1 , L. N. J. Wedmore 2 , K. J. W. McCaffrey 3 , R. M. J. Amey 1 , G. P. Roberts 4 , R. P. Shanks 5 , R. J. Phillips 1 , A. Hooper 1
Affiliation  

Cosmogenic exposure data can be used to calculate time‐varying fault slip rates on normal faults with exposed bedrock scarps. The method relies on assumptions related to how the scarp is preserved, which should be consistent at multiple locations along the same fault. Previous work commonly relied on cosmogenic data from a single sample locality to determine the slip rate of a fault. Here we show that by applying strict sampling criteria and using geologically informed modeling parameters in a Bayesian‐inference Markov chain Monte Carlo method, similar patterns of slip rate changes can be modeled at multiple sites on the same fault. Consequently, cosmogenic data can be used to resolve along‐strike fault activity. We present cosmogenic 36Cl concentrations from seven sites on two faults in the Italian Apennines. The average slip rate varies between sites on the Campo Felice Fault (0.84 ± 0.23 to 1.61 ± 0.27 mm yr−1), and all sites experienced a period of higher than average slip rate between 0.5 and 2 ka and a period of lower than average slip rate before 3 ka. On the Roccapreturo fault, slip rate in the center of the fault is 0.55 ± 0.11 and 0.35 ± 0.05 mm yr−1 at the fault tip near a relay zone. The estimated time since the last earthquake is the same at each site along the same fault (631 ± 620 years at Campo Felice and 2,603 ± 1,355 years at Roccapreturo). These results highlight the potential for cosmogenic exposure data to reveal the detailed millennial history of earthquake slip on active normal faults.

中文翻译:

使用宇宙成因核素暴露数据确定基岩岩溶带正断层的滑动历史

宇宙成因暴露数据可用于计算具有裸露基岩陡坡的正常断层的随时间变化的断层滑动率。该方法依赖于与如何保存坡度有关的假设,该假设在沿着同一断层的多个位置应保持一致。先前的工作通常依靠来自单个样本位置的宇宙成因数据来确定断层的滑动率。在这里,我们表明,通过应用严格的采样标准并在贝叶斯推断马尔可夫链蒙特卡罗方法中使用地质知悉的建模参数,可以在同一断层的多个位置对相似的滑移率变化模式进行建模。因此,宇宙成因数据可用于解决沿走向的断层活动。我们呈现宇宙的36来自意大利亚平宁山脉两个断层的七个位置的Cl浓度。平均滑坡率在Campo Felice断层上的各个站点之间有所不同(0.84±0.23至1.61±0.27 mm yr -1),并且所有站点经历的周期都高于平均滑坡率,介于0.5和2 ka之间,而周期小于平均滑坡率3 ka之前的滑移率。在Roccapreturo断层上,在靠近中继带的断层尖端处,断层中心的滑动率是0.55±0.11和0.35±0.05 mm yr -1。自上次地震以来的估计时间在同一断层的每个位置都相同(Campo Felice为631±620年,Roccapreturo为2,603±1,355年)。这些结果突出了潜在的宇宙成因数据,可以揭示活跃正断层的详细的千年滑动史。
更新日期:2021-03-10
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