The added value of time-variable microgravimetry to the understanding of how volcanoes work

Abstract

During the last few decades, 4D volcano gravimetry has shown great potential for illuminating subsurface processes at active volcanoes (including some that might otherwise remain “hidden”), especially when combined with other methods (e.g., ground deformation, seismicity, and gas emissions). By supplying information on changes in the distribution of bulk mass over time, gravimetry can provide unique information regarding such processes as magma accumulation in void space, gas segregation at shallow depths, and mechanisms driving volcanic uplift and subsidence. Despite its potential, 4D volcano gravimetry is an underexploited method, not widely adopted by volcano researchers or observatories. The cost of instrumentation and the difficulty in using it under harsh environmental conditions is a significant impediment to the exploitation of gravity at many volcanoes. In addition, retrieving useful information from gravity changes in noisy volcanic environments is a major challenge. While these difficulties are not trivial, neither are they insurmountable; indeed, creative efforts in a variety of volcanic settings highlight the value of 4D gravimetry for understanding hazards as well as revealing fundamental insights into how volcanoes work. Building on previous work, we provide a comprehensive review of 4D volcano gravimetry, including discussions of instrumentation, modeling and analysis techniques, and case studies that emphasize what can be learned from, campaign, continuous, and hybrid gravity observations. We are hopeful that this exploration of 4D volcano gravimetry will excite more scientists about the potential of the method, spurring further application, development, and innovation.