Collaborative Research: Characterizing fault zones at Kilauea and Mauna Loa volcanoes by large-scale mapping of earthquake stress drops and high precision locations

合作研究：通过地震应力降的大比例尺绘图和高精度位置来表征基拉韦厄火山和莫纳罗亚火山的断层带

• 批准号: 1045035
• 负责人: Peter Shearer
• 金额: $ 24.94万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-02-01 至 2015-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045035&HistoricalAwards=false
• 关键词: Collaborative; Research; Characterizing; fault; zones

Hawaii is one of the most active volcanic regions in the world, with the long-lived Pu'u' O'o-Kupaianaha eruption of Kilauea continuing since 1983. The magmatic activity is accompanied by high rates of earthquake activity and Hawaii has great value as a natural laboratory for studying the interactions between magmatic and tectonic processes. The seismic network operated by the U.S. Geological Survey (USGS) Hawaii Volcano Observatory (HVO) records thousands of events every year and since 1986 a substantial database of earthquake waveforms has accumulated. This project will involve analyses of these data to improve earthquake location accuracy and to resolve more details of earthquake source processes, such as the amount of stress that is relieved during faulting. The PIs will adopt a number of new methods that have been used successfully in the analysis of southern California seismicity and apply them to the Hawaiian dataset. The results from this study are expected to yield a sharper view of fault zone characteristics as well as generate a public database of information suitable for other researchers in their work at Hawaii.This project is a collaboration among U.C. San Diego, the University of Hawaii, and USGS HVO to apply a variety of newly developed seismic techniques to analyze waveforms from ~200,000 earthquakes recorded by the HVO seismic network in one of the most active volcanic regions in the world. These methods promise to greatly improve event location accuracy and to provide robust estimates of the patterns of earthquake stress drops, results that will help characterize fault-zone structures at Hawaii and help resolve the relationships between seismicity, volcanic activity, and strain transients. Our results will address the following questions: (1) Relocated microearthquakes in Hawaii will likely align along resolvable fault and/or conduit structures: what do these structures reveal about the tectonic and volcanic processes? (2) Are there repeating earthquakes with nearly identical waveforms, and can they be used to resolve temporal variations in seismic velocity associated with tectonic and volcanic activity? (3) How do the stress drops of Hawaiian earthquakes compare to other regions? Are there variations in earthquake stress drops that can be used to characterize stress field heterogeneity and identify regions of stress concentration? (4) Are earthquakes at Hawaii self-similar, such that average stress drop is constant with event size and large earthquakes are simply scaled up versions of smaller earthquakes? (5) What is the space/time evolution of seismicity at Hawaii? Are there consistent temporal variations in seismicity and earthquake properties related to ongoing volcanic activity and strain transients? How much of the observed clustering in the earthquake catalog can be explained by mainshock/aftershock triggering models (e.g., ETAS) and how much reflects possible physical triggers such as fluid migration or slow slip?

夏威夷是世界上最活跃的火山区之一，基拉韦厄火山持续时间较长的 Pu'u' O'o-Kupaianaha 喷发自 1983 年以来一直持续。岩浆活动伴随着高频率的地震活动，夏威夷具有巨大的价值作为研究岩浆和构造过程之间相互作用的天然实验室。 美国地质调查局 (USGS) 夏威夷火山观测站 (HVO) 运行的地震网络每年记录数千起事件，自 1986 年以来积累了丰富的地震波形数据库。 该项目将分析这些数据，以提高地震定位精度并解决地震源过程的更多细节，例如断层作用期间释放的应力量。 PI 将采用一些在南加州地震活动分析中成功使用的新方法，并将其应用于夏威夷数据集。这项研究的结果预计将更清晰地了解断层带特征，并生成适合夏威夷其他研究人员工作的公共信息数据库。圣地亚哥、夏威夷大学和 USGS HVO 应用各种新开发的地震技术来分析 HVO 地震网络在世界上最活跃的火山地区之一记录的约 200,000 次地震的波形。 这些方法有望大大提高事件定位精度，并提供对地震应力下降模式的可靠估计，结果将有助于表征夏威夷断层带结构，并有助于解决地震活动、火山活动和应变瞬变之间的关系。我们的结果将解决以下问题：（1）夏威夷重新定位的微地震可能会沿着可解析的断层和/或管道结构排列：这些结构揭示了有关构造和火山过程的什么信息？ （2）是否存在波形几乎相同的重复地震，它们是否可以用来解决与构造和火山活动相关的地震速度的时间变化？ (3) 夏威夷地震的应力降与其他地区相比如何？ 地震应力降的变化是否可用于表征应力场不均匀性并识别应力集中区域？ (4) 夏威夷的地震是否具有自相似性，即平均应力降随事件大小而变化，大地震只是小地震的放大版本？ (5) 夏威夷地震活动的时空演化是怎样的？ 与持续的火山活动和应变瞬变相关的地震活动和地震特性是否存在一致的时间变化？ 地震目录中观测到的聚集有多少可以通过主震/余震触发模型（例如 ETAS）来解释，有多少反映了可能的物理触发因素，例如流体迁移或慢滑移？