Autonomous Seafloor Geodesy System

超过70%的地球表面和90%的板块边界位于水下，使用标准的大地测量观测技术无法到达。俯冲带产生的地震和海啸是一些最具破坏性的自然灾害。大洋中脊是地球上最大的火山系统，而洋岛火山则带来了许多危险，同时也为研究岩浆和构造过程之间的相互作用提供了机会。俯冲带的关键科学问题包括：应力如何在结构内转移？长期滑动、地震和慢滑动事件扮演什么角色？对于大洋中脊和连接它们的转换断层，一些关键问题包括：海底扩张的阶段性如何？在年轻而薄的洋壳中，轴向谷边缘的断层和弹性应变之间是如何发生分离的？地震、地震滑动瞬变与热液流或附近的岩浆活动之间的关系是什么？海洋岛屿火山的关键问题是：构造和岩浆过程之间的关系是什么？只有在广阔的空间足迹中才能看到的深层岩浆过程在多大程度上控制着喷发的开始和结束？只有陆地的观测系统在观测海洋下发生的过程方面受到基本的几何限制。如果没有海底观测，我们对这些和类似结构的模拟和解释过程的能力将始终存在很大的不确定性。为了解决这些科学问题，我们必须对海底的水平和垂直运动进行具有成本效益的大地测量观测，我们将开始两个具体项目，努力解决其中一些广泛的问题。基拉韦厄火山经历了膨胀、收缩和侵入，其滑脱层表现出长期滑动、缓慢滑动事件和产生致命海啸的大地震。位于夏威夷基拉韦厄火山海底侧翼的GNSS-A和海底压力传感器网络将解决以下科学目标：1）与地震、长期蠕变和缓慢滑动事件有关的滑脱发生在哪里？2)这些过程如何在断层系统内传递应力？ 3)这些过程如何响应或影响火山事件？我们的第二个项目将探讨东南印度洋脊的两个短脊和转换段的海底扩张动力学。综合长期位移和应变的测量，以及来自微震活动和表面形态变化的脆性和累积变形，我们将解决大洋中脊的关键科学问题。

Over 70% of Earth's surface and 90% of plate boundaries are underwater and inaccessible using standard geodetic observing techniques. Subduction zones generate earthquakes and tsunamis that represent some of the most destructive natural hazards. Mid-ocean ridges represent the earth’s largest volcanic system, and ocean island volcanoes present numerous hazards, as well as opportunities for studying the interactions between magmatic and tectonic processes. Critical science questions for subduction zones include: How are stresses are transferred within the structures? What are the roles played by secular slip, earthquakes, and slow slip events? For mid-ocean ridges and the transform faults connecting them, some key questions include: How episodic is seafloor spreading? How does partitioning occur between the faults bordering the axial valley and the elastic strain in the young and thin oceanic crust? What are the relationships between earthquakes, aseismic slip transients and hydrothermal flow or nearby magmatic activity? Key issues for ocean island volcanoes are: What are the relationships between tectonic and magmatic processes? To what degree do deep magmatic processes - visible only with a wide spatial footprint - control the initiation and termination of eruptions? Land-only observation systems suffer from fundamental geometric limitations for observing processes occurring under the ocean. Without seafloor observations there will always be significant uncertainty in our ability to model and interpret the processes operating at these and similar structures. To address these science questions, we must acquire cost-effective geodetic observations of the horizontal and vertical motions of the seafloor.Two specific projects will begin our efforts to address some of these broad questions. Kilauea volcano experiences inflation, deflation, and intrusions, and its decollement exhibits secular slip, slow slip events and major earthquakes that have generated fatal tsunamis. A network of GNSS-A and seafloor pressure sensors on the submarine flank of Kilauea Volcano, Hawaii will address the following science goals: 1) Where on the decollement does slip connected with earthquakes, secular creep, and slow slip events occur? 2) How do these processes transfer stress within the fault system? 3) How do these processes respond to, or impact, volcanic events? Our second project will explore the dynamics of seafloor spreading at two short ridge and transform segments of the Southeast Indian Ridge. Integrating measurements of secular displacements and strain, and brittle and accumulated deformation from micro-seismicity and changes in surface morphology we will address the key science questions for mid-ocean ridges.