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

轴向海山是一座热点火山，也是胡安德富卡海洋扩张中心最具魔力的活动地貌。位于Axial的海洋天文台倡议(OOI)有线天文台提供了一个突破性的机会来捕捉海底喷发前、期间和之后的火山行为。轴向火山于1998年和2011年喷发，在2015年4月之前，海底传感器显示它再次充斥着岩浆。在运行的头六个月里，轴海山的有线地震仪记录到越来越高的小震活动率，支持了火山处于火山周期后期的推断。2015年4月下旬火山喷发时证实了这一点。这项拨款的研究人员将与研究生和本科生合作，分析这一首次使用海底传感器实时观测的海底火山事件。这项研究将使用OOI有线海底地震仪网络来确定海山轴线上的地震活动模式，以了解扩张轴上的应力是如何在空间和时间上划分的。将对热液流动可能存在的广泛结构的影响进行评估。将记录火山物理性质在火山循环中的变化，最终目的是促进有关单个地质事件如何相加以产生长期、稳定的海洋扩张的知识。为连续的OOI有线地震数据流制作近乎实时的地震目录，将能够快速识别重大新事件。重新定位分析将得出精确到几十米范围内的相对地震位置，使地震活动中的构造特征成为焦点。将获得震源机制、重复地震和横波分裂参数，以进一步限制火山的动力学。

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.