Integrated Studies of Transient Volcano Deformation in Hawaii

夏威夷火山瞬时变形的综合研究这项研究将高精度全球定位系统(GPS)和干涉合成孔径雷达(InSAR)测量与地震观测和力学模拟相结合，以更好地了解火山系统。该方法将数据收集和解释与理论分析和数值分析相结合。夏威夷过去10年与夏威夷火山观测站(HVO)合作收集的连续GPS测量表明：1)基拉韦厄火山的通胀和通货紧缩周期与P‘u’O‘o火山的喷发活动有关；2)莫纳罗亚火山开始达到顶峰通胀；3)基拉韦厄火山和莫纳罗亚火山的变形之间存在明显的时间相关性；4)基拉韦厄火山和毛纳罗亚火山南翼都向海运动；5)1997年喷发前8小时的裂谷伸展；伴随着这次喷发的快速通货紧缩和再膨胀；6)当山顶恢复喷发前状态时，P‘U’O‘O喷发恢复；7)1997年喷发后6个月的短暂裂谷伸展；8)一系列4次无声地震。无声地震的规模相当于5.7级，但每隔一到两天发生一次，而不是几秒钟。它们似乎在同一地区重复发生，紧接着向海上发生了一系列狭窄的地震。正在分析全球定位系统数据，以确定基拉韦厄半岛长期侧向形变和地震活动的震源位置。原始GPS相位数据用于确定事件持续时间。这项工作的另一个方面是看看无声事件是否与非火山震动或其他不寻常的地震信号有关。还分析了长期瞬时形变的来源，包括潜在的莫纳罗亚-基拉韦厄相互作用和岩浆构造相互作用。后者涉及InSAR和GPS的集成，并将测试从地震活动和其他地球物理和地质数据推断的特定构造模型。第二个焦点是成像和模拟伴随着堤防入侵的随时间变化的变形。分析力学模型被用来阐明决定堤坝是否到达地表并喷发或结束于入侵的因素，以及在这一过程发生时是否原则上可能确定这一点。时变反演方法已经发展起来，但大地测量数据的空间分辨率有限。包括伴随侵入的震群活动的位置有助于提高空间分辨率。Dieterich(1994)的理论提供了堤防诱发应力与地震活动性之间的关键环节。这使得人们可以反演出有关堤防形状、超额堤坝压力和其他参数的大地测量数据和地震率。最终目标是将观测结果与堤坝传播的物理模型联系起来。这项工作扩展了现有的集总参数模型，考虑了热效应和气泡作用引起的岩浆密度变化。这应该可以更好地了解岩脉的生长及其随时间的诱导变形，并量化控制喷发和入侵的因素。最后，该项目将更换协作GPS网络中出现故障的接收器，其中许多接收器已有十多年的历史。这个项目将支持两名博士生，其中一名专注于地震和非地震过程，包括无声地震，另一种是岩浆过程，包括堤坝入侵。四名过去或现在的博士S(3名女学生)至少部分是基于这个项目。此外，其他10名研究生或博士后也参与了这项研究。我们的研究完全是与HVO合作的，在过去的16年里，我们与6名项目科学家一起工作。

Integrated Studies of Transient Volcano Deformation in Hawaii This study combines high precision Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) measurements with seismic observations and mechanical modeling to better understand volcanic systems. The approach combines data collection and interpretation with theoretical and numerical analysis. Continuous GPS measurements collected over the past 10 years in Hawaii in a collaborative effort with the Hawaiian Volcano Observatory (HVO) have shown: 1) inflation and deflation cycles on Kilauea volcano correlated with eruptive activity at P'u 'O'o; 2) the onset of summit inflation at Mauna Loa volcano; 3) apparent temporal correlations between deformation at Kilauea and Mauna Loa; 4) seaward motion of both Kilauea and Mauna Loa south flanks; 5) eight hours of rift extension preceding an eruption in 1997; rapid deflation accompanying this eruption followed by re-inflation; 6) recovery of the P'u 'O'o eruption when the summit regained its pre-eruptive state; 7) six months of transient rift extension following the 1997 eruption; and 8) a series of four silent earthquakes. The silent earthquakes are equivalent in size to a magnitude 5.7 but occur over a period of 1 to two days, rather than a few seconds. They appear to repeat in the same area, immediately seaward of a narrow band of earthquakes. The GPS data are being analyzed to determine the source locations with respect to the sources of long-term flank deformation and seismicity on Kilauea. The raw GPS phase data are used to determine event durations. Another aspect of the work is to see if the silent events are associated with non-volcanic tremor or other unusual seismic signals. The sources of longer-term transient deformation, including potential Mauna Loa-Kilauea interactions and magmatic tectonic interactions are also being analyzed. The latter involve the integration of InSAR and GPS and will test specific structural models inferred from seismicity and other geophysical and geologic data. A second focus is imaging and modeling time dependent deformation accompanying dike intrusion. Analytical mechanical models are explored to elucidate the factors that determine whether a dike reaches the surface and erupts or ends with intrusion, and whether it is in principal possible to determine this while the process is occurring. Time dependent inversion methods have been developed, but the spatial resolution of geodetic data is limited. Including the locations of swarm seismicity accompanying intrusions helps to improve spatial resolution. Dieterich's (1994) theory provides the key link between dike induced stress and seismicity rate. This allows one to invert geodetic data and earthquake rates for the shape of the dike, the excess dike pressure, and other parameters. The final objective is relating the observations to physical models of dike propagation. This work extends extends existing lumped parameter models by including thermal effects and magma density changes induced by vesiculation. This should allow better understanding of the growth of dikes and their induced deformation with time, and to quantify the factors that govern eruption vs. intrusion. Lastly, the project will replace failing receivers in the collaborative GPS network, many of which are more than a decade old. This project will support two Ph.D. students, one focusing on seismic and aseismic processes including silent earthquakes, the other magmatic processes including dike intrusion. Four past or present Ph.D.'s (3 female students) were based at least in part on this project. In addition, 10 other graduate students or Postdocs have participated in this research. Our research is fully collaborative with HVO where we have worked with six project scientists over the past 16 years.