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Earthquake hazard from 36-Cl exposure dating of elapsed time and Coulomb stress transfer

36-Cl 暴露引起的地震危险、经过时间的测定和库仑应力传递

基本信息

批准号：
NE/I024127/1
负责人：
Gerald Roberts
金额：
$ 12.15万
依托单位：
Birkbeck, University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FI024127%2F1
关键词：
Earthquake hazard 36 Cl exposure

项目摘要

Overview: We request funds to make measurements of the elapsed time since major earthquakes on active faults in central Italy using 36-Cl cosmogenic dating, and calculate stress transfer from historical/palaeoseismic earthquakes. This will allow (1) knowledge transfer to at-risk communities in the region so they can prepare for future earthquakes if a fault with a long earthquake elapsed time has had stress transferred onto it by a neighboring earthquake(s), and (2) communication of this process to other regions with similar earthquake hazard. Technical Summary: Active faults experience earthquake rupture due to stress transfer from neighboring earthquakes only if the fault in question is close to its failure stress. We lack knowledge of which faults are close to their failure stress and thus cannot interpret calculations of stress transfer in terms of the probability of impending earthquakes. We propose, for an active normal fault system in central Italy, to measure the elapsed time since the last earthquake normalised to fault slip-rates using in situ 36-Cl cosmogenic isotope dating, because this is a proxy for how close a fault is to its failure stress. We will combine this with calculations of stress transfer from historical and palaeoseismic earthquakes in order to calculate which faults have the highest probability of rupture.Background: When an earthquake ruptures an active fault, stress is transferred onto neighboring active faults. This transfer of stress may cause a neighboring active fault to rupture in a subsequent earthquake. For example, the 2004 Boxing day earthquake on the subduction plate boundary near Sumatra caused severe loss of life on that day, but also triggered subsequent earthquakes in 2005, 2007, 2009 and 2010, each of which caused major loss of life. Such triggered earthquakes also occur on active faults within plates, such as the three 9th September > Mw 6 earthquakes in 1349 A.D. in central Italy, which occurred on the same day, but on different active faults; this has increased concern for the possibility of a future mainshock to follow the 2009 L'Aquila earthquake (Mw 6.3) whose ongoing aftershocks have transferred onto a neighboring fault (Fig. 1). A key point is that, despite the above examples, earthquakes do not always trigger subsequent earthquakes. Subsequent earthquakes only occur if the neighboring fault(s) are already close to failure due to long-term loading from motions in the crust or between plates. Identification of such faults could inform local populations and civil protection agencies in advance of a future earthquake allowing location-prioritised mitigation efforts. However, unfortunately, we cannot directly measure stress on a fault at 12-15 km depth where intra-plate mainshocks nucleate and so cannot identify such faults. However, we can measure a proxy for stress-through-time, that is elapsed time since the last earthquake, using cosmogenic isotopes (36-Cl). In the sub-surface, 36-Cl concentrations accumulate through time mainly due to hits on calcium atoms by cosmic particles. With 1-2 m slip in each earthquake on active normal faults, and with knowledge of 36-Cl production rates at depth, 36-Cl concentrations measured at 1-2 metres depth quantify elapsed time since the last earthquake. We can dig trenches to expose the fault plane to 1-2 metres depth and measure 36-Cl concentrations on the fault planes. If a neighboring earthquake has loaded/stressed a location with a high 36-Cl concentration, and hence a long elapsed time, we will be able to inform civil protection agencies responsible for planning mitigation; no such data are available at present. We can make such measurements, and have ongoing links with government civil protection project partners who make the seismic hazard maps for central Italy, and who are involved in communicating seismic hazard worldwide.

概述：我们要求资金使用36-CL宇宙成因测年来测量意大利中部活动断裂上的大地震以来经过的时间，并计算历史/古地震的应力转移。这将允许(1)将知识转移到该地区的高危社区，以便他们能够在经过较长地震时间的断层因邻近地震(S)而产生应力转移的情况下为未来的地震做好准备，以及(2)将这一过程传达给其他具有类似地震危险的地区。技术摘要：只有当所讨论的断层接近其破裂应力时，活动断层才会由于邻近地震的应力传递而发生地震破裂。我们缺乏关于哪些断层接近其破坏应力的知识，因此不能根据即将到来的地震的概率来解释应力转移的计算。对于意大利中部的活动正断层系统，我们建议使用原位36-Cl宇宙成因同位素测年来测量自上次地震归一化到断层滑动速率以来所经过的时间，因为这是断层与其破裂应力接近程度的替代。我们将把它与历史和古地震的应力转移计算结合起来，以计算哪些断层破裂的可能性最高。背景：当地震破裂活动断层时，应力转移到邻近的活动断层上。这种应力转移可能会导致邻近的活动断层在随后的地震中破裂。例如，2004年在苏门答腊岛附近俯冲板块边界发生的节礼日地震在当天造成了严重的生命损失，但也引发了随后在2005年、2007年、2009年和2010年发生的地震，每一次地震都造成了重大生命损失。这种触发地震也发生在板块内的活动断层上，例如公元1349年9月9日在意大利中部发生的三次6级地震，这三次地震发生在同一天，但发生在不同的活动断层上；这增加了人们对2009年L·阿奎拉地震(MW6.3)之后未来发生主震的可能性的担忧，该地震的持续余震已转移到邻近的断层上(图1)。关键的一点是，尽管有上述例子，地震并不总是触发后续的地震。只有当邻近的断层(S)由于地壳内或板块间运动的长期载荷而接近破裂时，才会发生后续地震。识别这些断层可以在未来的地震之前通知当地居民和民防机构，从而能够优先考虑地点的缓解工作。然而，不幸的是，我们不能直接测量12-15公里深的断层上的应力，在那里板内主震成核，因此无法识别这样的断层。然而，我们可以使用宇宙成因的同位素(36-Cl)来测量应力-时间的替代物，即自上次地震以来经过的时间。在次表面，36-氯浓度随着时间的推移积累，主要是由于宇宙粒子对钙原子的撞击。由于活动正断层上的每一次地震都有1-2米的滑动，并知道深部的36-氯的产生率，在1-2米深度测得的36-氯浓度可以量化自上次地震以来的过去时间。我们可以挖沟，使断裂面暴露在1-2米深的地方，并测量断裂面上的36-氯浓度。如果邻近的地震对36-氯浓度较高的地区施加了压力，因此经过了很长一段时间，我们将能够通知负责规划缓解的民防机构；目前还没有这样的数据。我们可以进行这样的测量，并与政府民用保护项目合作伙伴保持联系，这些合作伙伴为意大利中部制定地震危险地图，并参与在全球范围内传播地震危险。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

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