Autonomous Seafloor Geodesy System

• Subject Area: Geophysics and Geodesy
• Term: from 2022 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 505287286

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.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Autonomes System für Meeresbodengeodäsie
• Instrumentation Group: 0690 Sonstige geodätische und topographische Geräte
• Applicant Institution: Universität Stuttgart
• Leader: Professor Dr. James Foster