Linking geodetic observations with gas emissions to characterize magmatic activity at a subduction zone volcano: Mt. Baker (Washington)

对火山喷发的研究表明，地表温度高、气体排放、大地测量和地震动乱是深部岩浆活动的标志。很少有研究将非喷发火山的地球物理和地球化学测量结果联系起来。该项目是一项为期两年的试验性研究，旨在通过在华盛顿州贝克火山收集气体样本和大地测量来调查火山脱气和岩浆活动之间的关系。这座火山没有显示出历史上地震动乱的迹象，但活跃地排放二氧化碳和硫化氢的速度与其他火山的速度相似，其他火山的侵入是从地震活动中推断出来的。贝克山引起了人们的额外兴趣，因为1975年发生的气体排放和热活动莫名其妙的增加。这项研究的目的是收集足够的数据，以查明研究人员是否能够描述静止、脱气、俯冲带火山的重力变化和地表变形的模式，并评估气体排放与大地测量随时间变化之间的关系。研究人员将重新利用USGS电子测距仪(EDM)的站点，上一次调查是在1983年，使用GPS并进行微重力研究。首席调查员将与美国地质调查局的同事合作，收集火山上空空气中气体流量的重复测量，收集富马尔气体样本，并测量地面温度。将对天然气的成分和氦同位素比率进行分析。当这些数据集与大地测量一起考虑时，可以通过类比的方式了解贝克山和其他火山的岩浆系统。GPS和重力测量与气体地球化学的结合有可能彻底改变我们对火山过程的理解。然而，以前很少有研究试图将静止火山的热和气体排放与大地测量数据联系起来；因此，这项研究可能对理解火山过程和潜在的危险有很大的好处。此外，这些结果可能被用来推断1975年导致贝克山气体/热能骚乱的机制。Mt.Mt.贝克是华盛顿州西北部和不列颠哥伦比亚省下部大陆最重大的火山灾害，这里居住着超过250万人。长期的社会效益可能包括提高预测未来火山活动特征的能力。

Research at erupting volcanoes has shown that high surface temperatures, gas emissions, and geodetic and seismic unrest are signatures of magmatic activity at depth. Few studies have correlated such geophysical and geochemical measurements at non-erupting volcanoes. This project is a 2-year pilot study to investigate the relationship between volcano degassing and magmatic activity by collecting gas samples and geodetic measurements at Mount Baker volcano, Washington. The volcano has shown no signs of historical seismic unrest, yet actively emits both carbon dioxide and hydrogen sulfide at rates similar to other volcanoes where intrusions have been inferred from seismicity. Mount Baker is of additional interest because of an unexplained increase in gas emissions and thermal activity that occurred in 1975. The goals of this study are to gather sufficient data to discern whether the investigators will be able to characterize the patterns of gravity change and surface deformation at a quiescent, degassing, subduction zone volcano, and evaluate the relationship between gas emission and geodetic changes over time. The researchers will reoccupy USGS electronic distance meter (EDM) sites, last surveyed in 1983, with GPS and also conduct microgravity studies. The principle investigator will collaborate with US Geological Survey colleagues to collect repeat airborne gas flux measurements over the volcano and collect fumarole gas samples and measure temperatures on the ground. Gas will be analyzed for composition and helium isotope ratios. When these datasets are considered together with geodetic observations, much can be learned about the magmatic system at Mount Baker and other volcanoes by analogy.The integration of GPS and gravity measurements with gas geochemistry has the potential to revolutionize our understanding of volcanic processes. However, few previous studies have attempted to correlate thermal and gas emissions with geodetic data at quiescent volcanoes; therefore, therefore this research may have a significant benefit to the understanding of volcanic processes and, potentially, hazards. Further, the results may be used to infer the mechanisms that caused the gas/thermal unrest at Mount Baker in 1975. Mt. Baker represents the most significant volcanic hazard to northwest Washington and the lower mainland of British Columbia, home to more than 2.5 million people. Long-term societal benefits may include enhanced ability to predict the character of future volcanic activity.