RAPID: Probing magma plumbing and seismicity beneath Mt. St. Helens with modern exploration industry seismometers

众所周知，要绘制火山下岩浆管道系统的三维图像非常困难，因为要揭示岩浆系统的细节，需要对大范围的地震事件进行高密度的观测。与此同时，了解这些岩浆系统至关重要，因为它们在确定圣海伦斯火山等火山造成的危害的性质和严重程度方面起着关键作用。该项目使用现代勘探工业地震仪，在圣海伦斯山周围崎岖的地形上提供密集的爆炸和自然地震观测。这些数据将被交付给IRIS数据管理中心，从而为地震界提供一种潜在的下一代地震阵列的经验，用于结构和震源研究。新墨西哥大学的一个由本科生和研究生、一名博士后学者和PI组成的团队正在与一家勘探行业服务公司（加州长滩NodalSeismic公司）合作部署这些仪器。学生们将有机会参加圣海伦斯山的大型多机构实地考察活动，并体验一家创新服务公司的运营。几乎所有新墨西哥大学的参与者都在为新墨西哥大学高年级本科生和研究生开设的一门新的地震学课程中使用这些数据，本科生参与者也在高年级研究项目中使用这些数据。该项目部署了大约1000个费尔菲尔德节点地震仪（节点），在St. Helens火山约15公里范围内密集排列，连续记录两周，以获得岩浆管道系统和周围地壳的详细三维地震样本。此次部署利用了由美国国家科学基金会资助的iMUSH项目引爆的24个可控震源，这些节点可以连续两周记录频繁的当地地震活动和环境噪声。在MSH周围15公里内部署1000个节点，极大地提高了利用基于波场的方法对岩浆管道系统进行三维成像的机会，并实现了对地震活动位置和机制的高分辨率约束，从而可以深入了解弧火山下的熔体/流体输送过程。

It is notoriously difficult to construct 3-D images of the magma plumbing systems that exist beneath volcanoes because uncovering the details of the magma system requires highly dense observations of a wide range of seismic events. At the same time, understanding these magma systems is vital because they play key roles in determining the nature and severity of hazards posed by volcanoes like Mt. St. Helens. This project is using modern exploration industry seismometers to provide dense observations of explosions and natural earthquakes in the rugged terrain around Mt. St. Helens. The data are being delivered to the IRIS Data Management Center, thereby providing the seismic community experience with a potential type of next-generation seismic array for structure and source studies. A team of undergraduate and graduate students, a postdoctoral scholar, and the PI from University of New Mexico are deploying the instruments in collaboration with an exploration industry service company (NodalSeismic of Long Beach, California). Students are gaining the opportunity to participate in a large multi-institution field campaign at Mt. St. Helens and experience with the operations of an innovative service company. Nearly all the UNM participants are also using the data in a new seismology class for senior undergraduates and graduate students at UNM, and undergraduate participants are also using the data for senior research projects. This project is deploying about 1,000 Fairfield Nodal seismometers (nodes) to record continuously for two weeks in a dense array within about 15 km of Mt. St. Helens in order to obtain detailed 3-D seismic sampling of the magma plumbing system and surrounding crust. The deployment is leveraging 24 controlled sources detonated by the NSF-funded iMUSH project, and the nodes are providing 2 weeks of continuous recording of frequent local seismicity and ambient noise. Deployment of 1,000 nodes in the inner 15 km around MSH is greatly improving opportunities for 3-D imaging of the magma plumbing system with wave-field based methods and enabling high-resolution constraints on locations and mechanisms of seismicity that could provide insight into melt/fluid transport processes beneath arc volcanoes.