COLLABORATIVE RESEARCH: Geodetic measurements and mechanical models of the volcano deformation cycle

阿拉斯加的奥克莫克火山似乎每十年左右就会喷发一次，最近一次是在1997年，第二次是在2008年。它的活动已经使用现代方法进行了监测，形成了丰富的观测数据集。研究人员正在开发一种地球物理模型，该模型应该可以解释大多数观测到的活动的时间和位置。这项研究的新信息将直接与了解位于繁忙的北太平洋空中交通走廊下的Okmok和其他类似火山构成的时间相关的火山危险有关。同样类型的模型应该适用于其他显示周期性活动的火山，如阿拉斯加的Westdahl或冰岛的Hekla。奥克莫克是进行这种实验的极好的天然实验室，因为已经使用大地测量和地震手段监测了一个完整的形变周期。利用丰富的观测数据集和正式的数值模拟方案，研究人员正在研究奥克莫克火山，以解决以下问题：(1)奥克莫克火山内部物质性质的分布情况？(2)滞弹性流变学如何改变变形场的时间演化？(3)深度物质性质如何影响地表观测到的变形？(4)描述岩浆室的模型参数的不确定性是什么？脉冲响应流变学实验将提高对火山变形周期的理解。具体地说，该研究项目将检验四个假设：(I)1997年喷发后的变形在2008年喷发之前没有达到稳定状态。(Ii)粘弹性应力松弛有助于在同喷发时间间隔和喷发后时间间隔期间观察到的瞬时变形。(3)岩浆房的有效粘度比周围的地壳小几个数量级。(Iv)1997年喷发期间从锥体A喷发出来的熔岩流产生的应力场有利于岩浆从岩浆室向锥体D的扩散。结果将发表在国际同行评议的文献中。来自科学、技术、工程和数学专业(STEM)的一名研究生将接受地震学、大地测量学和火山学三个学科交叉的地球物理研究职业生涯的培训。建模方案和方法将在业务层面上向科学界传播。研究员马斯特拉克是一名初级教员，来自激励竞争研究实验计划办公室(EPSCoR)资助的一个机构，他将提供如何将有限元方法应用于火山变形的短期课程。来自代表性不足群体的申请者将被特别鼓励参加。该项目将加强调查人员和美国地质调查局科学家之间的合作

Okmok volcano in Alaska appears to erupt every decade or so, most recently in 1997 and again in 2008. Its activity has been monitored using modern methods, forming a rich observational data set. The investigators are developing a geophysical model that should explain the timing and location of most of the observed activity. The new information from this study will be directly relevant to understanding time-dependent volcanic hazard posed by Okmok and other, similar volcanoes lying beneath the heavily-used north Pacific air traffic corridors. The same type of model should be applicable to other volcanoes displaying cyclic activity, such as Westdahl in Alaska or Hekla in Iceland. Okmok is an excellent natural laboratory for such an experiment because a complete cycle of deformation has been monitored using geodetic and seismic means. Using this rich observational data set and a formal protocol for numerical modeling, the investigators are studying Okmok volcano to address the following questions: (1) What is the distribution of material properties within Okmok? (2) How does anelastic rheology modify the temporal evolution of the deformation field? (3) How do material properties at depth influence the deformation observed at the surface? (4) What are the uncertainties of the model parameters that describe the magma chamber?The impulse-response rheological experiment will improve understanding of the volcano deformation cycle. Specifically, the research project will test four hypotheses: (I) Deformation following the 1997 eruption did not reach a steady state before the eruption in 2008. (II) Viscoelastic stress relaxation contributes to the transient deformation observed during the co-and post-eruptive time intervals. (III) The effective viscosity is several orders of magnitude smaller in the rind of the magma chamber than in the surrounding crust. (IV) The lava flow extruded from Cone A during the 1997 eruption produces a stress field that favors dike propagation from the magma chamber to Cone D.The results will be published in the international, peer-reviewed literature. A graduate student from a group under-represented in Science, Technology, Engineering and Mathematics (STEM) will be trained for a career in geophysical research at the intersection of three disciplines: seismology, geodesy and volcanology. The modeling protocol and approach will be disseminated among the scientific community at an operational level. Investigator Masterlark, a junior faculty member from an institution funded by the Office of Experimental Program to Stimulate Competitive Research (EPSCoR), will offer a short course on how to apply the Finite Element Method to volcanic deformation. Applicants from underrepresented groups will be especially encouraged to participate. The project will enhance collaboration between the investigators and scientists at the U.S. Geological Survey