Bardarbunga Eruption Response: Monitoring of post-rifting deformation and activity at Askja Volcano with continuous GPS

地球的岩石圈被分解成相对移动的构造板块。在板块界面处，它们的运动决定了板块边界带的特征：收敛（俯冲）、变换（走滑）或发散（扩张）。裂谷期表明在不同板块边界（这里是欧亚大陆和北美）的构造板块活跃扩张时期。这样的事件非常罕见，而且很难观察到，因为大多数裂谷带都被海洋覆盖。该RAPID项目将协助快速安装连续GPS （cGPS）站，以记录冰岛中部Holuhraun裂谷Bárðarbunga火山口持续喷发时的地壳运动。动荡时期始于2014年8月16日，岩浆侵入从Bárðarbunga火山口蔓延了约40公里，并向北接近Askja火山口约10公里。该堤坝可能在2014年8月26日引发了4.6级地震，并在Askja引发了微震活动。研究者加入了冰岛气象局的一个国际科学家合作项目；冰岛大学；新西兰GNS科学；和亚利桑那大学，他们共同记录了由这次裂谷事件引起的地壳运动。在安装新站点之后，冰岛气象局将把遥测数据用于减轻灾害和保护公民。将首次用大地测量仪器连续监测Askja的活动和可能的变化。因为Askja？火山口湖和浅层岩浆库重新激活的可能性，爆炸活动是一个威胁，可能会影响航空旅行和更远的人口。这些数据将有助于评估Askja的喷发潜力，并进一步使科学界能够重新评估1975-85年克拉夫拉大火和2005年阿法尔裂谷事件之后的观测结果，为板块扩张机制提供独特而罕见的一瞥。该项目的主要动机是扩大现有的cGPS网络，以捕捉(1)裂谷事件对Askja岩浆系统造成的应力变化的影响，以及(2)裂谷周围下地壳和上地幔在裂谷后松弛的非线性过程的开始。利用所有合作者的支持，我们计划安装总共8个遥测cGPS站点。将在Askja安装3个站点（一个在火山口，一个在东侧，一个在南侧）。4个站点将安装在裂谷以东15-40公里范围内的不同纬度。最后一个地点将填补裂谷以西的一个缺口；位于Askja和Bárðarbunga之间，距离裂谷约20公里。拟议的cGPS站点的快速部署对于监测这一事件的演变，区分导致整体变形场的过程，以及（重要的）解释从战役GPS或InSAR获得的暂时有限的观测结果将是无价的；特别是因为InSAR只在没有积雪的时候有效。这些数据为科学界对裂谷事件的详细调查奠定了基础。分析下地壳和上地幔黏性弛豫的早期非线性特征，对于推导出裂陷后瞬变过程模型具有重要意义。这样的模型对于正确解释更广泛地区的任何后续变形至关重要，该地区充满了火山和冰川均衡调整过程。此外，利用本项目提供的变形资料，还可以研究区域岩脉侵入引起的静态和瞬态变化对区域应力场的影响，以及对邻近火山系统、火山系统的岩浆产量和地壳储存能力的影响。

Earth's lithosphere is broken up into tectonic plates that move relative to one another. At the plate interfaces their motion determines the character of the plate boundary zone: convergent (subduction), transform (strike-slip), or divergent (spreading). Rifting episodes indicate periods of active spreading of tectonic plates at divergent plate boundaries (here Eurasia and North America). Such events are incredibly rare and difficult to observe as most rift zones are covered by ocean. This RAPID award assists with the prompt installation of continuous GPS (cGPS) stations to record crustal motions in response to the ongoing eruption of the Icelandic Bárðarbunga Caldera at the Holuhraun rift in Central Iceland. The period of unrest initiated on August 16, 2014 as a magma intrusion propagated ~40 km from Bárðarbunga Caldera and approached to within about 10 km of Askja Caldera to the north. The dike likely caused a M4.6 earthquake on August 26, 2014, and associated microseismicity at Askja. The investigator joins an international collaboration of scientists at the Icelandic Meteorological Office; the University of Iceland; GNS Science, New Zealand; and the University of Arizona who collectively record crustal motions induced by this rifting episode. After installation of the new sites, the Icelandic Meteorological Office will use the telemetered data for hazard mitigation and civil protection purposes. Activity and possible changes at Askja will, for the first time, be monitored continuously with geodetic instruments. Due to Askja?s caldera lake and the likelihood of reactivation of shallow magma reservoirs, explosive activity is a threat that could affect air travel and more distant populations. The data will help assess the eruptive potential of Askja, and furthermore enable the scientific community to re-evaluate observations made after the 1975-85 Krafla Fires and the 2005 Afar rifting episodes, providing a unique and rare glimpse into the mechanisms of plate spreading.The main motivation of the project is in the expansion of the existing cGPS network to capture (1) the impact of the stress changes due to the rifting event on Askja's magmatic system and (2) the onset of the nonlinear process of post-rifting relaxation of the lower crust and upper mantle around the rift. Leveraging support from all collaborators, we plan to install a total of 8 telemetered cGPS sites. 3 sites will be installed at Askja (one in the caldera, one at the eastern flank, one at the southern flank). 4 sites will be installed at different latitudes within 15-40 km to the East of the rift. The last site will fill a gap to the west of the rift; in between Askja and Bárðarbunga, about 20 km from the rift. Rapid deployment of the proposed cGPS sites will be invaluable to monitor the evolution of this event, distinguish processes that contribute to the overall deformation field, and -importantly- to interpret temporally limited observations from campaign GPS or InSAR; especially since InSAR is only effective during times of no snow cover. These data lay the foundation for detailed investigation of the rifting event by the scientific community. Analysis of the early stages of the non-linear characteristics of viscous relaxation in the lower crust and upper mantle is important to derive a model for the post-rifting transient. Such a model is crucial to correctly interpret any subsequent deformation in broader region, which is riddled with volcanic and glacial isostatic adjustment processes. Furthermore, the impact of the static and transient changes to the regional stress field induced by the regional dike intrusion and their impact on neighboring volcanic systems, their magma production and crustal storage capacity can be studied with the deformation data provided through this project.