Intrusion and Eruption Dynamics on Active Galapagos Volcanoes

知识价值：该项目涉及对加拉帕戈斯群岛两座不同的活火山进行大地测量和地球物理监测，以了解岩浆的运输和储存，以及浅层侵入和喷发之间的平衡，所有这些都对火山灾害评估具有重要意义。自2000年以来，塞拉利昂内格拉火山的全球定位系统观测显示，通货膨胀率在过去两年里急剧上升，2005年4月16日达到顶峰，岩浆室屋顶沿着活板门断层发生非弹性破坏，随后在秋季喷发。破火山口底板的断裂作用可能对破火山口下岩浆储集层的岩浆储存和脱气历史产生深远影响。一种假设是，活门断裂松弛了与侵入和膨胀相关的弹性应力，允许更多的岩浆储存在火山内部，而不是喷发。对火山气体排放和重力变化的连续测量，以及对现有GPS网络的更新，将提供验证这一假设的手段。该项目的第一阶段将通过维护2002年安装的连续的L1和L1/L2全球定位系统网络和开展后续全球定位系统运动，继续监测内格拉山脉的形变。GPS结果将与InSAR测量结果相结合，以便利用该技术的空间复盖范围。同时测量从气孔中释放的火山气体将监测脱气过程，以响应浅层岩浆储集层的体积变化。重力测量将对水库在深度的体积和质量变化提供补充约束。这项研究的结果将对岩浆和建筑物的材料性质、与不同充填率有关的地球化学和力学变化以及建筑物破坏导致入侵或喷发的原因和后果提供约束。费尔南迪纳火山于2005年5月13日从位于破火山口西南边缘的裂隙系统喷发。这种形式的喷发喷口被称为环状裂缝，在加拉帕戈斯屏蔽式火山中很常见，被认为是由作用于火山内部的压力所控制的，既有斜坡上的重力，也有岩浆室的膨胀。一种假设是，作为应变场相互作用的结果，发生在加拉帕戈斯盾火山下侧的环状裂缝和放射状侵入共存。有趣的是，1995年费尔南迪纳火山的上一次喷发是从西南侧的放射状喷发裂缝开始的，就在2005年喷发地点的正下方。安装在费尔南迪纳的GPS活动网络之前得到了NSF的资助，旨在捕捉到像刚刚发生的那样的周向事件，火山喷发附近有密集的地点阵列。在费尔南迪纳，将实施喷发后GPS活动，以更好地了解应变场和裂缝形成的机制。更广泛的影响：拟议的项目将为授予博士学位的机构、本科学院和厄瓜多尔大学的学生和教职员工提供合作研究体验，并与查尔斯·达尔文研究站协调，继续在游客和当地居民的教育项目中开展外联工作。

Intellectual Merit: This project concerns geodetic and geophysical monitoring of two distinct active volcanoes in the Galapagos Islands to understand magma transport and storage, and the balance between shallow intrusion and eruption, all of which have important implications for volcanic hazards assessment. GPS observations at Sierra Negra volcano since 2000 showed a dramatic increase in the rate of inflation over the past two years, culminating on April 16, 2005 with inelastic failure of the magma chamber roof along a trapdoor fault, and subsequent eruptions in the Fall. Faulting of the caldera floor may have a profound effect on magma storage and the degassing history of the subcaldera magma reservoir. One hypothesis is that trapdoor faulting relaxes elastic stress related to intrusion and inflation, allowing larger volumes of magma to be stored inside the volcano instead of erupting. Serial measurements of volcanic gas emissions and gravity changes, along with updates to existing GPS networks will provide means to test this hypothesis. The first phase of the project will continue monitoring of deformation at Sierra Negra by maintaining the continuous L1 and L1/L2 GPS network installed in 2002 and conducting a follow-up GPS campaign. The GPS results will be integrated with InSAR measurements in order to take advantage of the spatial coverage of that technique. Simultaneous measurement of volcanic gases emitted from fumaroles will monitor degassing processes in response to volume changes in the shallow magma reservoir. Gravity measurements will provide complementary constraints on volume and mass changes in the reservoir at depth. Results of this study will provide constraints on the material properties of the magma and edifice, geochemical and mechanical changes related to variable rates of chamber filling, and the causes and consequences of edifice failure leading to intrusion or eruption.Fernandina volcano began erupting on May 13, 2005 from a fissure system located on the southwestern caldera rim. This form of eruptive vent, termed a circumferential fissure, is common to Galapagos shield volcanoes and is thought to be governed by stresses acting within the volcano from both gravitational forces on the slopes and magma chamber inflation. One hypothesis is that circumferential fissures and radial intrusions, which occur on the lower flanks of Galapagos shield volcanoes, coexist as the result of strain field interaction. Interestingly, the previous eruption of Fernandina in 1995 was from a radial eruptive fissure on the southwest flank, immediately below the site of the 2005 eruption. The GPS campaign network installed at Fernandina with prior NSF funding was designed to capture a circumferential event like the one that has just occurred, with a dense array of sites in the vicinity of the eruption. At Fernandina, a post-eruption GPS campaign will be implemented to better understand the strain field and mechanisms of fissure formation. Broader Impacts: The proposed project will provide collaborative research experience for students and faculty from Ph.D.-granting institutions, undergraduate colleges, and Ecuadorian universities, and in coordination with the Charles Darwin Research Station to continue outreach efforts in educational programs for visitors and local residents.