Ocean island volcanoes initiate and grow over time periods of 105 to 106 years, requiring a long-lived magmatic plumbing system to transport magma from the mantle to the surface. Only a fraction of the magma, however, is erupted; magma is stored in crustal magma chambers, or trapped near the crust-mantle boundary. These magma intrusions grow the crust, and change the state of stress. The increase in pressure accompanying magma intrusion inflates the volcanic edifice, triggering earthquakes and eruptions. The geometry of the magma chambers and conduits, therefore, is fundamental to the development of predictive models of volcano deformation and eruption. Our integrated seismic and geodetic data acquisition and modelling project aims to image the magma plumbing system beneath the most rapidly deforming hotspot volcano system in the world: Sierra Negra volcano in the Galapagos Archipelago. Existing SAR data provide high-resolution images of surface deformation over broad regions, and GPS provides continuous time series of vertical and horizontal deformation. We cannot, however, differentiate between the basaltic volcano growth models without complementary seismic information on the distribution and mechanisms of seismic strain, as well as the crust and upper mantle structure. We will deploy and maintain 16 broadband seismometers for two years, recording seismic waves from local and distant earthquakes to illuminate the magmatic plumbing system and state of stress within the lithosphere beneath Sierra Negra volcano to understand the stress interaction between shallow magma intrusion, extrusion, and intra-caldera faulting processes. The anticipated results are a new 4D model of Sierra Negra?s shallow and deep magmatic system that satisfies seismic and geodetic observations, and is constrained by earthquake locations, focal mechanisms, wavespeed and ambient noise tomography, seismic anisotropy, receiver function estimates of sill and Moho depths, and existing petrological data. We will determine the time-varying state of stress within and around the volcano in response to magma intrusion and withdrawal, including the dynamic relationship between trapdoor faulting and magma intrusion Broader Significance and Importance Ocean island volcanoes initiate and grow over time periods of 105 to 106 years, requiring a long-lived magmatic plumbing system to transport magma from the mantle to the surface. Only a fraction of the magma, however, is erupted; magma is stored in crustal magma chambers, or trapped near the crust-mantle boundary. These magma intrusions grow the crust, and change the state of stress. The increase in pressure accompanying magma intrusion inflates the volcanic edifice, triggering earthquakes and eruptions. Sierra Negra volcano in the Galapagos Archipelago is the most rapidly deforming of these ocean island volcanoes. Continuous monitoring of earthquake and surface deformation is vital to deduce the geometry of the magma chambers and conduits, and the physical changes to the volcano edifice itself. These data, in turn, inform predictive models of volcano deformation and eruption worldwide. Our continuous seismic, satellite, GPS monitoring and modeling project has been designed to maximize the broader impacts, which fall into 3 areas: volcanic hazards, education, and international collaboration. Nearly a million people live on active basaltic volcanoes; understanding the relationship between magma supply, state of stress and eruptions is vital for hazard assessment, including the potential for tsunami-generating flank instabilities. The baseline provided by the geodetic and seismic monitoring is essential to development of a volcanic hazard mitigation program in the Galápagos Archipelago, and other basaltic volcanoes worldwide. This project will provide a collaborative opportunity for US undergraduate, graduate, and Ecuadorian students. Students from both countries will benefit from experience with the realities of field-based geophysics, gaining valuable skills in seismology and geodesy that can be translated to the workplace or advanced degree programs.
This work is co-funded by the Geophysics and Geochemistry Programs and the Americas Program of the Office of International Science and Engineering.
