The earthquake cycle and the evolution of fault friction at Kilauea Volcano, Hawaii

夏威夷基拉韦厄火山的地震周期和断层摩擦演化

• 批准号: 1824114
• 负责人: James Foster
• 金额: $ 36.94万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-15 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1824114&HistoricalAwards=false
• 关键词: earthquake; cycle; evolution; fault; friction

Every year a number of earthquakes cause devastation, much of it due to collapsing buildings, with economic impacts in the United States alone adding up to about $4.4 billion dollars a year. Earthquake cycle monitoring and earthquake forecasting is an active topic of geological research, and is crucial to guide our efforts to both prepare society and its infrastructure for earthquakes, and to also mitigate the impacts. It is not currently possible to make deterministic predictions of when and where earthquakes will happen. It is however, possible to make probabilistic forecasts about the likelihood of earthquakes happening in a specified area over a specified period. The accuracy of these statistical estimates is strongly dependent on our understanding of the history of a particular fault system, its current state, and its likely evolution. This picture is generated through historical records, current observations of the accumulation of stresses in the crust, and models that guide our understanding of where stresses are being stored and how a fault is likely to respond to them. Although each major fault has its own unique context, what we learn from studying one fault in detail moves our understanding of the broader processes forward. The frictional properties of a fault, and how these vary spatially and temporally throughout the earthquake cycle, are key parameters for understanding its likely behavior. The researchers will leverage the wealth of modern and historical geodetic data from the south flank of Kilauea Volcano, Hawaii, covering 100+ years, and use both analytical and numerical models to investigate the temporal evolution of the frictional properties of the underlying decollement and its relationship to the earthquake cycle. The Broader Impacts of this project span hazards, collaborations with the USGS and support for undergraduate and graduate students. Kilauea's decollement is a major source of natural hazards to the state, as it generates major earthquakes, like the May 4, 2018 Mw6.9 Leilani Estates earthquake, and also fatal tsunamis. Understanding its evolution and relationship to the catastrophic landslide features found throughout the islands is of great societal importance.Current interpretation of geological and geophysical observations from Kilauea's south flank suggests that continuous creep, slow slip events (SSEs), and major earthquakes are all occurring on the same fault plane, with combinations of at least two of these processes operating simultaneously. How these processes are connected and interact, and the implications for the mechanics and evolution of the wedge and its earthquake cycle, are fundamental questions that must be answered to improve our understanding of these processes. The physical conditions at the shallow depths of the decollement make Kilauea an extremely unusual outlier compared to most other convergent margin sources of slow slip events. In addition, the SSEs here appear to occur up-dip of the locked zone, a region largely inaccessible to geodetic measurements in subduction zones. This study, therefore, offers an opportunity to gain new insights through comparing and contrasting fault processes with those elsewhere. Preliminary modeling of the current secular surface displacements suggests that the patches of the decollement creeping in these motions outline the zones that currently exhibit SSEs. This implies the currently active portion of the decollement can be mapped into four distinct zones with frictional properties that span velocity-weakening to velocity-strengthening behavior and include the transitional zone(s) that are thought to support SSEs. This project suggests that friction on the decollement can be described using a rate-and-state formalism. They will model geodetic data from different eras within the earthquake cycle to test this hypothesis and answer the following questions: 1) What ranges of parameters for the fault plane rheology adequately predict the observed secular creep rates, SSEs, and microseismicity? 2) How have these parameters evolved from the locked state prior to 1975 through to current? 3) What magmatic overpressures in the lower rift zone are compatible with flank deformation rates?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

每年，许多地震造成破坏，其中大部分是由于建筑物崩溃而导致的，仅在美国，经济影响每年总计约44亿美元。 地震周期监测和地震预测是地质研究的一个积极主题，对于指导我们为社会及其基础设施进行地震做好准备以及减轻影响至关重要。目前不可能对地震何时何地进行确定性预测。但是，有可能对指定时期内指定区域发生地震发生的可能性进行概率预测。这些统计估计的准确性在很大程度上取决于我们对特定断层系统，其当前状态及其可能演变的历史的理解。这张图是通过历史记录，当前对地壳中压力积累的观察以及指导我们对压力的理解存储位置以及故障如何响应它们的理解的模型。尽管每个主要故障都有其独特的环境，但是我们从研究一个错误中学到的东西会使我们对更广泛的过程的理解向前发展。断层的摩擦特性，以及这些在整个地震周期中如何在空间和时间上变化，是理解其可能行为的关键参数。研究人员将利用夏威夷基拉韦阿火山南侧面的现代和历史大地测量数据的财富，覆盖100多年，并使用分析和数值模型来研究基本分解的摩擦特性的时间进化及其与地震周期的关系。该项目的更广泛影响涵盖了危害，与USGS的合作以及对本科生和研究生的支持。 Kilauea的脱土是该州自然危害的主要来源，因为它会产生主要地震，例如2018年5月4日MW6.9 Leilani Estates地震以及致命的海啸。了解它的演变和与整个岛屿上发现的灾难性滑坡特征的关系至关重要。对Kilauea的南侧的地质和地球物理观察的流动解释表明，持续的蠕变，慢滑动事件（SSES），主要地震（SSES），并且主要地震都在同一断层上发生，并且与这些过程的组合相结合。这些过程如何连接和相互作用，以及对楔子的力学和地震周期的力学和演变的含义，是必须回答的基本问题，以提高我们对这些过程的理解。与大多数其他慢速速度事件的收敛余量来源相比，脱土深度的物理条件使Kilauea变得非常不寻常。此外，这里的SSE似乎发生在锁定区域的上浸区，该区域在俯冲带中的大地测量区域基本上无法接近。因此，这项研究提供了一个机会，通过将故障过程与其他地方进行比较和对比，从而获得新的见解。当前的世俗表面位移的初步建模表明，在这些运动中，脱土的斑块概述了当前显示SSE的区域。这意味着解体的当前活性部分可以映射到四个不同的区域，具有摩擦特性，这些区域跨越了速度涉及速度的速度强度加强行为，并包括被认为支持SSES的过渡区。该项目表明，可以使用速率和状态形式主义来描述对脱土的摩擦。他们将对地震周期内不同时代的测量数据进行建模，以检验这一假设并回答以下问题：1）断层平面流变学的参数范围充分预测了观察到的世俗蠕变率，SSES和微震震？ 2）这些参数如何从1975年之前的锁定状态演变为当前？ 3）下层裂谷区域中哪些岩浆过压与侧面变形率兼容？该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，被认为值得通过评估来获得支持。