The seismic and petrological signature of magma migration beneath the Reykjanes Peninsula, Iceland

雷克雅那半岛位于冰岛西南部，如果包括附近的首都雷克雅未克，居住着全国60%以上的人口。从地质学的角度来看，该半岛以中大西洋山脊体系的一部分为特色，形成了北美和欧亚构造板块之间的边界。它由一系列分段的火山带勾勒出来，以地壳严重破裂为特征，并包含与历史性喷发事件有关的裂缝。有趣的是，证据表明这些喷发以大约800年的间隔周期性地发生。根据最近一次喷发的熔岩测年，它可以追溯到13世纪。2019年末，沿着雷克扬斯半岛检测到地震活动加剧，可能与地壳深处的岩浆侵入有关。在接下来的12个月里，这一活动反复起伏，包括几次规模较大的地震，包括今年2月雷克雅未克发生的5.7级地震。在过去的几个月里，这一活动逐渐升级，每天都能检测到数千次地震，并伴随着一条10公里长的1.0-1.5公里深的堤坝的入侵。2021年3月19日，这一活动在位于堤坝南端的Fagradalsfjall附近的一次喷发中达到顶峰，这是整个半岛约800年来的第一次喷发。这场规模较小但壮观的喷发仍在进行中(例如，4月5日，两个新的火山裂缝在原喷发点约700米处打开)，并伴随着地震活动和火山震动(与地壳熔体通过有关的持续震动)。该项目的目标是在雷克雅尼斯半岛活动增加的地区部署一系列地震台。这将使我们能够记录与构造断层上破裂的地震相关的地面运动，构造断层构成板块边界的一部分，以及地壳中的岩浆迁移。我们还将使用强大的显微镜来绘制新喷发的熔岩样本的成分变化图。岩浆和晶体的组成告诉我们岩浆在向地表移动并喷发之前被储存的深度。单个晶体的地图可以用作“地质秒表”，以计时岩浆在喷发前上升的时间，我们的新方法将应用于正在进行的喷发。通过结合地震和熔岩的岩浆运动证据，我们可以建立岩浆系统如何工作的模型，并为冰岛和其他地方未来更有效的火山监测战略提供信息。这些进展可能有助于我们了解火山活动的周期性，未来喷发和可能对周围人口中心构成危险的大地震的可能性，以及板块边界系统和火山系统之间相互作用的性质，后者是由下地壳和下地幔中熔融(岩浆)水平升高所推动的。

The Reykjanes Peninsula is located in southwest Iceland, and if one includes the nearby capital city of Reykjavik, hosts more than 60% of the population of the entire country. From a geological perspective, the peninsula features a segment of the Mid-Atlantic Ridge system that forms the boundary between the North American and Eurasian tectonic plates. It is delineated by a series of segmented volcanic zones featuring crust that is heavily fractured and contains fissures associated with historic eruptive episodes. Intriguingly, evidence points to these eruptions occurring periodically with an interval of approximately 800 years. Dating of lava from the most recent eruption places it in the 13th century.In late 2019, elevated earthquake activity along the Reykjanes Peninsula was detected, possibly associated with magma intrusion deep in the crust. Over the subsequent 12 months, this activity repeatedly waxed and waned, and included several sizable earthquakes, including a magnitude 5.7 that shook buildings in Reykjavik in February this year. In the last several month, this activity has gradually escalated, with thousands of earthquakes being detected every day, and was accompanied by the intrusion of an ~10 km long dike at a depth of 1.0-1.5 km. On 19th March 2021, this activity culminated in an eruption near Fagradalsfjall, located at the southern end of the dike, the first on the entire peninsula in ~800 years. This relatively small but spectacular eruption is ongoing (for instance, two new volcanic fissures opened up approximately 700m from the original eruption site on April 5th), and is accompanied by earthquake activity and volcanic tremor (continuous shaking associated with the passage of melt in the crust).The goal of this project is to deploy an array of seismic stations in the region of elevated activity on the Reykjanes Peninsula. This will allow us to record ground motion associated with earthquakes that rupture on tectonic faults, which form part of the plate boundary, and magma migration in the crust. We will also use powerful microscopes to map out the compositional variation in samples of newly-erupted lava. The composition of the magma and the crystals tell us about the depths that the magma was stored before it moved towards the surface and erupted. Maps of individual crystals can be used as "geological stop-watches" to time how long magma took to rise before eruption and our new methods to do this will be applied to the ongoing eruption. By combining evidence for magma movement from the earthquakes and lava, we can build models of how the magmatic system works and inform more effective future volcano monitoring strategies in Iceland and elsewhere. Such advances may help us to understand the periodicity of the volcanic activity, the potential for future eruptions and large earthquakes that may pose a hazard to surrounding population centres, and the nature of the interaction between the plate boundary system and the volcanic system, the latter fueled by elevated levels of melt (magma) in the lower crust and mantle beneath.