Collaborative Research: Understanding the Spatio-Temporal Characteristics of Earthquakes at Axial Seamount Late in an Eruptive Cycle

轴向海山是胡安·德富卡洋壳扩张中心的热点火山，也是最活跃的岩浆活动特征。海洋观测站倡议（OOI）在轴电缆观测站提供了一个开创性的机会，捕捉火山行为导致，期间和之后的海底喷发。轴火山在1998年和2011年爆发，在2015年4月之前，海底传感器显示它再次膨胀岩浆。在运作的头六个月里，轴海山的电缆地震仪记录到越来越高的小地震活动率，支持了该火山处于火山周期后期的推断。2015年4月下旬火山爆发时证实了这一点。这项研究的研究人员将与研究生和本科生合作，分析这一首次通过海底传感器实时观察到的海底火山事件。这项研究将使用OOI海底电缆地震仪网络来确定Axial Seamount的地震活动模式，以了解扩展轴的应力是如何在空间和时间上分配的。将评估热液流可能的广泛结构方面的影响。将记录火山在一个火山周期中物理性质的变化，最终目的是增进关于个别地质事件如何叠加产生长期稳定的海洋扩张的知识。为持续的OOI电缆地震数据流制作近实时地震目录将允许快速识别重要的新事件。重新定位分析将产生精确到几十米以内的相对地震位置，使地震活动中的结构特征成为焦点。将获得震源机制、重复地震和剪切波分裂参数，以进一步约束火山的动力学。

Axial Seamount is a hotspot volcano and the most magmatically active feature on the Juan de Fuca oceanic spreading center. The Ocean Observatories Initiative (OOI) cabled observatory at Axial provides a ground-breaking opportunity to capture volcano behavior leading up to, during, and following a seafloor eruption. Axial volcano erupted in 1998 and 2011 and, prior to April 2015, seafloor sensors showed that it was inflating with magma again. Over their first six months of operation, the cabled seismometers at Axial Seamount recorded increasingly high rates of small earthquake activity, supporting the inference that the volcano was in the late stage of its volcanic cycle. This was confirmed in late April 2015 when the volcano erupted. The researchers on this grant will work with both graduate and undergraduate students to analyze this first-ever seafloor volcanic event to be observed in real-time with seafloor sensors.This study will use the OOI cabled ocean bottom seismometer network to determine the pattern of earthquake activity at Axial Seamount to understand how stress at the spreading axis is partitioned spatially and temporally. The implications in terms of possible broad structures of hydrothermal flow will be assessed. Changes in the physical properties of the volcano through a volcanic cycle will be documented, with ultimate aim of advancing knowledge about how individual geologic events sum to produce long-term, steady oceanic spreading. Production of near-real time earthquake catalogs for the continuing OOI cabled seismic data stream will allow rapid identification of significant new events. Relocation analysis will yield relative earthquake locations accurate to within tens of meters, bringing structural features in the seismicity into focus. Focal mechanisms, repeating earthquakes, and shear wave splitting parameters will be obtained to further constrain the volcano's dynamics.