Constraints on absolute magma chamber volume from geodetic measurements: Trapdoor faulting in the Galapagos

大地测量对绝对岩浆房体积的限制：加拉帕戈斯群岛的活板门断层

• 批准号: 1829763
• 负责人: Paul Segall
• 金额: $ 11.94万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829763&HistoricalAwards=false
• 关键词: Constraints; absolute; magma; chamber; volume

As magma rises from the Earth's mantle it accumulates in magma chambers in the Earth's crust. As magma pressure in these chambers increases it causes the Earth's surface to bulge upward, a process termed "inflation". Inflation can be measured with a variety of instruments, both ground-based and space based, and is a useful predictor of impending eruptions. Standard analysis methods can be used to derive the change in volume during an inflation episode but are insensitive to the total chamber volume. It would be extremely useful to scientists and those monitoring volcanic hazards to know the volume of active magma chambers. The total volume provides an upper bound on the possible eruptive volume and is a constraint on models of magma chamber evolution. This project uses unique observations at Sierra Negra volcano in the Galapagos to place rigorous bounds on the total volume of Sierra Negra's magma chamber. The Broader Impacts of this study are particularly timely because the observations suggest that an eruption and/or earthquake at Sierra Negra may be imminent. The volcano has been uplifting since mid-2015 and is now higher than it was prior to the most recent (2005) eruption. The project also supports a graduate student to work on this problem.Between 1992 and the 2005 eruption Sierra Negra uplifted by nearly 5 meters, with maximum uplift in the center of the caldera. This data is well fit by a shallow sill-like magma chamber with its top at roughly 2 km depth. Inflation has been punctuated by three trapdoor faulting events, with slip along an intra-caldera fault system. The most recent trapdoor event occurred only 3 hours prior to the 2005 fissure eruption. The response of the magma chamber to the faulting depends on both the volume of the chamber and the compressibility of the magma contained within and is clearly expressed in observable surface displacements. By constraining the relative compressibility of the magma and the elastic chamber, which can be achieved with observations from the 2005 eruption, the researchers will be able to estimate the absolute chamber volume. This will permit estimation of the fraction of total magma that was erupted in 2005, a useful parameter for forecasts at other volcanoes.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.

随着岩浆从地球上升起时，它会在地壳中的岩浆室中积聚。 随着这些腔室中的岩浆压力增加，它会导致地球表面向上凸起，这一过程称为“通胀”。 通货膨胀可以用各种基于地面和空间的工具来衡量，并且是即将发出的有用预测指标。 标准分析方法可用于在通货膨胀发作期间得出体积的变化，但对总腔室体积不敏感。 对于科学家和监测火山危害的人来说，知道活动岩浆腔的数量将非常有用。 总体积在可能的喷发体积上提供了上限，并且是岩浆腔室演化模型的限制。 该项目在加拉帕戈斯山区的塞拉内格拉火山（Sierra Negra Volcano）使用独特的观察结果，以对塞拉内格拉（Sierra Negra）岩浆室的总体积进行严格的界限。 这项研究的更广泛影响尤其及时，因为观察结果表明塞拉内格拉山脉的喷发和/或地震可能即将到来。 自2015年中期以来，该火山一直在升起，现在比最近（2005年）爆发之前高。该项目还支持一名研究生来解决这个问题。1992年与2005年爆发塞拉内格拉（Sierra Negra）之间的工作，近5米，在火山口的中心最大的隆起。 该数据非常适合浅层窗台状的岩浆室，其顶部大约为2 km。 三个陷阱门故障事件使通货膨胀率打断，并沿着电池内断层系统滑动。 最近的陷阱门事件发生在2005年裂口爆发前3小时。 岩浆腔对断层的响应取决于腔室的体积和内部包含的岩浆的可压缩性，并且在可观察的表面位移中明确表示。 通过限制岩浆和弹性室的相对可压缩性，这可以通过2005年喷发的观测来实现，研究人员将能够估计绝对腔室的体积。 这将允许估计2005年爆发的总岩浆的比例，这是其他火山预测的有用参数。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子来评估来支持的，并具有更广泛的影响。