Collaborative Research: High resolution passive seismic imaging beneath Valles Caldera

Valles火山口是北美三座超级火山之一，有着悠久的火山活动历史，有记载的岩浆流动最近可达7万年。地震成像可以通过使用地震波来可视化火山地下结构，就像医学成像中的超声波成像一样。直到最近，山谷火山口还缺乏地震成像，这反过来又阻碍了对熔体体积、熔化程度的估计和对管道系统的了解。2019年，德克萨斯大学埃尔帕索分校(UTEP)/新墨西哥大学(UNM)联合部署了97个地震仪线路，横跨整个火山口1个月。这一举措的一个主要目标是解决破火山口下熔体的空间范围和集中问题，以及其他悬而未决的问题，包括穹顶下的任何岩浆体的深度、破火山口内充填物和破碎的基底块体的厚度，以及壳幔边界的性质。利用尖端技术，研究人员探测并揭示了火山的地下岩浆系统，并促进了UTEP和UNM这两个少数族裔服务机构之间的合作。该项目的成果改进了该地区的地震和火山灾害评估，并支持对来自人数不足的少数民族的研究生和本科生进行科学方面的培训。Valles火山口是第四纪活跃的超级火山，是复兴的火山口的教科书例子。在过去的20年里，它基本上躲过了地震的审查。在这里，研究人员探索了Valles火山口下的岩浆系统。它们量化了熔体结构的空间范围、散射边界的深度和位置，并评估了破火山口系统假定的抗震性质。利用环境噪声地震干涉术来估计长周期Rayleigh波和Love波的频散曲线；这些频散曲线将在带有接收器函数、H/V比和噪声自相关的跨维贝叶斯方案中联合反演。其目标是准确地估计山谷破火山口下的速度结构。目标包括通过剪切波速度和Vp/Vs估计来确定熔体的空间范围和浓度，通过散射波分析来确定岩浆构造和火山口充填的深度，以及探测和定位任何可能揭示岩浆和流体运动的局部地震活动。该项目是对洛斯阿拉莫斯国家实验室较稀疏的长期地震监测工作的补充。它是一种教育读物，也是对经常使用火山口作为天然实验室的地球物理野外训练营的补充。它的结果改进了对火山生命周期阶段的评估，并使其能够更好地与其他第四纪超级火山进行比较。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Valles caldera is one of three supervolcanoes in North America and has a long history of volcanism with documented magma flows as recent as ~70,000 years. Seismic imaging allows visualization of volcanic subterranean structures by using seismic waves in a similar way ultrasound sonography in medical imaging. Seismic imaging of the Valles Caldera was lacking until recently, which in turn has hindered estimate of melt volumes, melt extent, and understanding of the plumbing system. A joint University of Texas at El Paso (UTEP)/University of New Mexico (UNM) deployment in 2019 resulted in a 97-seismometer line crossing the entire caldera for 1 month. A primary objective of this initiative is to resolve the spatial extent and concentration of melt under the caldera, with other standing questions including the depth of any magma body underlying the dome, the thickness of intra-caldera fill and fractured basement blocks, and the nature of the crust/mantle boundary. Using cutting edge techniques, researchers probe and unveil the subterranean magmatic system of the volcano and foster a collaboration between UTEP and UNM, two minority serving institutions. The outcomes of this project improve earthquake and volcanic hazard assessment in the region, and support the training of graduate and undergraduate students from underrepresented minorities in science. The Valles caldera, a Quaternary-active supervolcanoes, is the textbook example of a resurgent caldera. It has largely escaped seismic scrutiny in the past two decades. Here the researchers probe the magmatic system beneath Valles caldera. They quantify the spatial extent of melt structures, the depth and emplacement of scattering boundaries, and assess the assumed aseismic nature of the caldera system. Ambient noise seismic interferometry is leveraged to estimate dispersion curves for long period Rayleigh and Love waves; these will be jointly inverted in a transdimensional Bayesian scheme with receiver functions, H/V ratios, and noise autocorrelations. The goal is to accurately estimate velocity structures under the Valles caldera. Targets include bounding the spatial extent and concentration of melt through shear-wave velocity and Vp/Vs estimates, depth to magmatic structures and caldera fill under the resurgent dome through scattered wave analysis, and detection and location of any local seismicity that may reveal magma and fluid movements. This project complements sparser long-term seismic monitoring efforts by Los Alamos National laboratory. It serves as an educational primer and complement to frequent geophysics field camps using the caldera as a natural laboratory. Its outcomes improve the assessment of the volcano life-cycle stage and allow better comparison with other Quaternary supervolcanoes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.