Collaborative Research: Earthquake Catalog and Waveform Analysis to Assess the Evolution of Axial Seamount Surrounding the 2015 Eruption

轴海山是一座活跃的海底火山，位于美国西海岸的胡安·德富卡山脉扩张中心。Axial最近被安装用于连续实时数据监测，作为NSF赞助的海洋观测计划（OOI）的电缆海洋观测网络的一部分，其中包括高质量的海底地震数据，以及一套无与伦比的海底大地测量和热液测量。该海山过去曾定期喷发，但当地地震网络捕捉到了2015年4月/5月的最近一次喷发，并提供了一个独特的数据集，可用于调查与海底火山有关的喷发和岩浆机制。该项目将分析地震性质和统计模式在空间和时间上的演变，以及这些变化如何与整个喷发周期的变形和热液产出相关联。这些数据将用于跟踪火山建筑物内的应力变化和岩浆运动，从而更好地了解海底火山的力学和海底喷发的动力学。该项目利用了最近启用的大洋协会轴向海山电缆阵列数据门户，将有助于海底监测的科学基础设施。该项目为社区学院学生、本科生和研究生提供研究经验，并为中学科学教师提供地震物理学和海底火山过程方面的培训。该项目将利用汇编的轴向海山地震目录，进行波形分析，以评估2015年4月和5月火山爆发之前、期间和之后火山系统的演变，包括地震、海底变形和热液活动之间的许多联系。应力状态将通过监测地震活动率的变化和地震统计模式的变化来推断。断层的强度和/或流体的运动将通过震源参数研究来限制。该项目将推进三个技术目标：1）使用一种新的技术组合，包括地震活动/应力率变化、地震应力降测量和地震b值研究，研究2015年轴向海山喷发期间火山地壳内的应力演变。2)调查的断层系统内的破火山口的动态应力的背景下，他们的本地应力的历史，并通过纳入热液时间序列观测，提供新的限制流体在动态触发的作用。3)探索与2015年火山爆发相关的爆炸性声学事件的特殊记录。虽然有越来越多的证据表明火山爆发在深海中很常见，但很少有直接的观察。了解这些信号的分布和缩放可能会改变我们对洋中脊环境中喷发动力学的看法。

Axial seamount is an active submarine volcano located off the west coast of the US on the Juan de Fuca midocean ridge spreading center. Axial has recently been instrumented for continuous real-time data monitoring as part of the cabled ocean observatory network of the NSF-sponsored Ocean Observatory Initiative (OOI) that includes high-quality ocean bottom seismic data, as well as an unrivaled set of seafloor geodetic and hydrothermal measurements. The seamount has erupted periodically in the past but the most recent eruption in April/May 2015 was captured by the local seismic network and provides a unique dataset with which to investigate the eruption and magmatic mechanisms associated with submarine volcanoes. The project will analyze the evolution of earthquake properties and statistical patterns in space and time, as well as how these changes are correlated with deformation and hydrothermal outputs throughout the eruption cycle. These data will be used to track changes in stress and the movement of magma within the volcanic edifice, leading to a better understanding of the mechanics of submarine volcanoes and the dynamics of eruptions on the seafloor. This project takes advantage of the recently enabled OOI Axial seamount cabled array data portal and will contribute to scientific infrastructure for undersea monitoring. The project provides research experience for community college students, undergraduates and graduate students, and training for middle-school science teachers in the areas of earthquake physics and submarine volcanic processes. This project will utilize the compiled Axial Seamount seismic catalog and carry out waveform analysis to assess the evolution of the volcanic system before, during and after the April and May 2015 eruption including the many linkages between earthquakes, seafloor deformation and hydrothermal activity. Stress states will be inferred by monitoring changes in seismicity rate and variations in earthquake statistical patterns. The strength of the faults and/or the movement of fluids will be constrained through earthquake source parameter studies. This project will advance three technical goals: 1) Study the evolution of stress within the volcanic crust through the 2015 eruption at Axial Seamount using a novel combination of techniques, including seismicity/stressing rate changes, earthquake stress drop measurements and seismic b-value studies. 2) Investigate the response of fault systems within the caldera to dynamic stresses in the context of their local stressing history, and by incorporating hydrothermal time series observations that provide new constraints on the role of fluids in dynamic triggering. 3) Explore the exceptional record of explosive acoustic events associated with the 2015 eruption. Although there is increasing evidence that explosive volcanism is common in the deep-sea, there are few direct observations. Understanding the distribution and scaling of these signals may transform our views on eruption dynamics in mid-ocean ridge environments.