Testing Theoretical models for Earthquake Clustering using Cl-36 Cosmogenic Exposure Dating of Active Normal Faults in Central Italy

使用意大利中部活动正断层的 Cl-36 宇宙成因暴露测年法测试地震集群的理论模型

• 批准号: NE/E01545X/1
• 负责人: Patience Cowie
• 金额: $ 37.8万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FE01545X%2F1
• 关键词: Testing; Theoretical; models; Earthquake; Clustering

It is difficult to predict the timing of future destructive earthquakes (>Ms 6.0) because earthquakes on any given fault cluster in time (Figure 1). Variability in earthquake recurrence intervals due to clustering is poorly known because we lack data on the timing of earthquakes on any given fault over a sufficient time period that several earthquakes will have happened. This lack of knowledge hinders probabilistic forecasts of earthquake occurrence because the intrinsic variability in recurrence intervals, the Coefficient of Variation, CV, is a key parameter for input into probabilistic calculations (e.g. Ellsworth et al. 1999). What we do know is that large numbers of palaeo-earthquakes on individual faults can be dated by measuring the cosmogenic 36Cl concentration, but such data are very rare. Uplift along an active normal fault during an earthquake causes the rocks that were buried beneath the ground surface to be exposed to cosmic rays. The rocks that become exposed, accumulate 36Cl through time due to interaction of cosmic particles with the atoms within the rock minerals. Thus the concentration of 36Cl reveals the age of exposure of the rock at the Earth's surface. Steps in exposure age profiles reveal the timing of large earthquakes that offset the ground surface in the past. Such stepped exposure age profiles provide earthquake records that are an order of magnitude longer than historical earthquake records (e.g. a single 36Cl profile constrained 7 palaeoearthquakes since 12-18 ka on the Velino Fault, Italy [Palumbo et al. 2004; Fig. 2]). The historical record, which is complete since 1349 A.D., reveals only 1 earthquake since then (1904 A.D., Ms 5.5). The Velino fault does not typify other active normal faults in Italy, because it is a new fault that slips relatively slowly (~0.3 mm/yr average vertical motion since 12-18 ka), and it is growing to link 2 long-established faults that are slipping at 1-2 mm/yr since 12-18 ka. Our initial numerical modelling shows that such linking-faults have different values for CV than the main basin-bounding normal faults. We propose to collect field 36Cl data and conduct numerical modelling that will allow us to test how and why recurrence variability is controlled by fault geometry and fault growth/linkage. Faults in central Italy are ideal because (1) fault scarps amenable to 36Cl dating are abundant (Palumbo et al. 2004, Papanikolaou et al. 2005), (2) fault geometries and growth histories are well constrained (Cowie and Roberts 2001, Roberts and Michetti 2004), (3) the P.I. and Co.I's have established links with Italian Government earthquake agencies, and have access to both 36Cl and scarp mapping equipment in Edinburgh and Durham, (4) The P.I. has existing numerical model runs that already show how CV varies with fault geometry and fault growth, (5) we have experience in using earthquake recurrence for mapping earthquake probabilities (Roberts et al. 2004). We will collect 36Cl profiles from newly-growing, linking faults, and long-established active faults to establish spatial variability in CV related to fault geometry. We have identified sites where surface exposure has been solely through surface faulting and not erosion/sedimentation cycles. Laser-mapping (LiDAR) and field mapping will further constrain the sample sites and optimise the sampling strategy. Numerical modelling will constrain the physics of why CV varies between newly-growing, linking faults, and long-established active faults. We will iteratively compare field and numerical results, to constrain the underlying physics that determines the recurrence in each circumstance. We will calculate earthquake probabilities using the recurrence variability, CV, and map seismic hazard and how it varies across the fault geometry, using our findings to assess seismic hazard worldwide.

很难预测未来破坏性地震（>Ms 6.0）的时间，因为任何给定断层上的地震都会在时间上聚集（图1）。由于聚类，地震复发间隔的可变性知之甚少，因为我们缺乏足够长的时间内发生几次地震的任何给定断层上地震发生时间的数据。这种知识的缺乏阻碍了地震发生的概率预测，因为复发间隔的内在变异性，变异系数CV是输入概率计算的关键参数（例如Ellsworth等人，1999）。我们所知道的是，通过测量宇宙成因的36 Cl浓度，可以确定单个断层上大量古地震的日期，但这样的数据非常罕见。地震时，沿活动正断层沿着会使埋在地表下的岩石暴露在宇宙射线之下。由于宇宙粒子与岩石矿物中原子的相互作用，暴露出来的岩石会随着时间的推移积累36 Cl。因此，36 Cl的浓度揭示了岩石暴露在地球表面的年龄。暴露年龄剖面中的台阶揭示了过去发生的大地震偏移地表的时间。这种阶梯式暴露年龄剖面提供的地震记录比历史地震记录长一个数量级（例如，意大利Velino断层上自12-18 ka以来，单一36 Cl剖面限制了7次古地震[Palumbo等人，2004;图2]）。自公元1349年以来完整的历史记录，自那时以来只发生过一次地震（公元1904年，Ms 5.5）。Velino断层并不代表意大利的其他活动正断层，因为它是一个相对缓慢滑动的新断层（自1 - 2 -18 ka以来平均垂直运动约为0.3 mm/年），并且它正在增长，以连接自1-2 -18 ka以来以1-2 mm/年滑动的两个长期存在的断层。我们最初的数值模拟表明，这种连接故障有不同的CV值比主要的盆地边界的正断层。我们建议收集现场36 Cl数据，并进行数值模拟，这将使我们能够测试如何以及为什么复发的变化是由断层几何形状和断层生长/链接控制。意大利中部的断层是理想的，因为（1）适合36 Cl测年的断层陡坎丰富（Palumbo等人，2004年，Papanikolaou等人，2005年），（2）断层几何形状和生长历史受到很好的约束（Cowie和Roberts，2001年，Roberts和Michetti，2004年），（3）P.I.和Co.I's已经与意大利政府地震机构建立了联系，并且可以使用爱丁堡和达勒姆的36 Cl和陡崖测绘设备。已有的数值模型运行已经显示了CV如何随断层几何形状和断层生长而变化，（5）我们有使用地震复发绘制地震概率图的经验（Roberts et al. 2004）。我们将收集36 Cl配置文件从新成长的，连接故障，和长期建立的活动断层，以建立空间变异CV断层几何形状。我们已经确定的网站，表面暴露已完全通过表面断层，而不是侵蚀/沉积循环。激光测绘（LiDAR）和实地测绘将进一步限制采样点，优化采样策略。数值模拟将限制为什么CV在新生长的连接断层和长期存在的活动断层之间变化的物理原因。我们将迭代地比较场和数值结果，以约束在每种情况下确定复发的基础物理。我们将使用复发变异性计算地震概率，CV，并绘制地震危险性图，以及它如何在断层几何形状上变化，使用我们的研究结果来评估全球地震危险性。

项目成果

QUaternary fault strain INdicators database - QUIN 1.0 - first release from the Apennines of central Italy.

• DOI: 10.1038/s41597-022-01311-8
• 发表时间: 2022-05-12
• 期刊: SCIENTIFIC DATA
• 影响因子: 9.8
• 作者: Lavecchia, Giusy;Bello, Simone;Andrenacci, Carlo;Cirillo, Daniele;Ferrarini, Federica;Vicentini, Noemi;de Nardis, Rita;Roberts, Gerald;Brozzetti, Francesco
• 通讯作者: Brozzetti, Francesco

Orogen-scale uplift in the central Italian Apennines drives episodic behaviour of earthquake faults.

• DOI: 10.1038/srep44858
• 发表时间: 2017-03-21
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Cowie PA;Phillips RJ;Roberts GP;McCaffrey K;Zijerveld LJ;Gregory LC;Faure Walker J;Wedmore LN;Dunai TJ;Binnie SA;Freeman SP;Wilcken K;Shanks RP;Huismans RS;Papanikolaou I;Michetti AM;Wilkinson M
• 通讯作者: Wilkinson M

The tectonic geomorphology of bedrock scarps on active normal faults in the Italian Apennines mapped using combined ground penetrating radar and terrestrial laser scanning

• DOI: 10.1016/j.geomorph.2014.03.011
• 发表时间: 2015-05-15
• 期刊: GEOMORPHOLOGY
• 影响因子: 3.9
• 作者: Bubeck, A.;Wilkinson, M.;Sammonds, P.
• 通讯作者: Sammonds, P.

Surface faulting earthquake clustering controlled by fault and shear-zone interactions

断层和剪切带相互作用控制的地表断层地震群

• DOI: 10.31223/osf.io/qkx2v
• 发表时间: 2024
• 作者: Mildon Z

Viscous roots of active seismogenic faults revealed by geologic slip rate variations

• DOI: 10.1038/ngeo1991
• 发表时间: 2013-12-01
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Cowie, P. A.;Scholz, C. H.;Steer, P.
• 通讯作者: Steer, P.