Synthesis of global satellite observations of magmatic and volcanic deformation: implications for volcano monitoring & the lateral extent of magmatic domains

Abstract

Global Synthetic Aperture Radar (SAR) measurements made over the past decades provide insights into the lateral extent of magmatic domains, and capture volcanic process on scales useful for volcano monitoring. Satellite-based SAR imagery has great potential for monitoring topographic change, the distribution of eruptive products and surface displacements (InSAR) at subaerial volcanoes. However, there are challenges in applying it routinely, as would be required for the reliable operational assessment of hazard. The deformation detectable depends upon satellite repeat time and swath widths, relative to the spatial and temporal scales of volcanological processes. We describe the characteristics of InSAR-measured volcano deformation over the past two decades, highlighting both the technique's capabilities and its limitations as a monitoring tool. To achieve this, we draw on two global datasets of volcano deformation: the Smithsonian Institution Volcanoes of the World database and the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics volcano deformation catalogue, as well as compiling some measurement characteristics and interpretations from the primary literature. We find that a higher proportion of InSAR observations capture non-eruptive and non-magmatic processes than those from ground-based instrument networks, and that both transient (< month) and long-duration (> 5 years) deformation episodes are under-represented. However, satellite radar is already used to assess the development of extended periods of unrest and long-lasting eruptions, and improved spatial resolution and coverage have resulted in the detection of previously unrecognised deformation at both ends of the spatial scale (~10 to > 1000 km 2 ). 'Baseline' records of past InSAR measurements, including 'null' results, are fundamental for any future interpretation of interferograms in terms of hazard‚ both by providing information about past deformation at an individual volcano, and for assessing the characteristics of deformation that are likely to be detectable (and undetectable) using InSAR. More than half of all InSAR deformation signals attributed to magmatic processes have sources in the shallow crust (< 5 km depth). While the depth distribution of InSAR-derived deformation sources is affected by measurement limitations, their lateral distribution provides information about the extent of active magmatic domains. Deformation is common (24% of all potentially magmatic events) at loci ≥5 km away from the nearest active volcanic vent. This demonstrates that laterally extensive active magmatic domains are not exceptional, but can comprise the shallowest part of trans-crustal magmatic systems in a range of volcanic settings.

Satellite Geodesy Captures Offset Magma Supply Associated With Lava Lake Appearance at Masaya Volcano, Nicaragua

“…The detection of an offset magma reservoir with respect to current locus of activity has been observed in other caldera settings, as well as volcanic centers associated with some form of a caldera, ranging 2–8 km from the locus of activity, for example, Aniakchak (Kwoun et al, ), Cerro Blanco/Robledo (Pritchard & Simons, ), Hudson (Delgado et al, ; Pritchard & Simons, ), Kilauea (Poland et al, , ), Makushin (Lu, Power, et al, ), Mauna Loa (Amelung et al, ), Nyamulagira (Wauthier et al, ), Okmok (Lu et al, ), and Uzon (Pritchard & Simons, ), to name a few. Despite the fact that this seems to be relatively common at volcanic centers (e.g., Ebmeier et al, ), the exact conditions and preexisting structures required for the presence of an offset magma chamber are still poorly understood. Our study highlights the importance of monitoring a volcanic region over a broad area and longer timespan in order to capture the full extent of the magma plumbing system and associated magma transport and storage processes.…”

“…Deformation at volcanic centers is often observed spatially and temporally in conjunction with volcanic activity and is generally attributed to magma transport and storage in the magma plumbing system (Pyle et al, , and references therein). The observation of deformation centers offset from the main area of activity has become more prevalent with the usage of satellite remote sensing techniques such as Interferometric Synthetic Aperture Radar (InSAR) (e.g., Ebmeier et al, ). Previous studies show that offset magma chambers are associated with a variety of different volcanic settings: calderas (e.g., Delgado et al, ; Kwoun et al, ; Lu et al, ; Poland et al, , ; Pritchard & Simons, , , ), stratovolcanoes (e.g., Delgado et al, ; Lu, Power, et al, ; Lu, Wicks, et al, ; Nishimura et al, ; Pritchard & Simons, ; Sparks et al, ; Wicks et al, ), shield volcanoes (e.g., Amelung et al, ; Wauthier et al, ), or unclearly related to a specific volcanic center (e.g., Pritchard & Simons, ).…”

Structural and Geochemical Interactions Between Magma and Sedimentary Host Rock: The Hovedøya Case, Oslo Rift, Norway

“…Directly observing magma‐induced deformation itself near the propagating intrusion front in the subsurface is currently impossible. Instead, the resulting surface displacement induced by magma intrusion is monitored by using satellite sensors and inverted numerically to characterize the subsurface magma bodies (e.g., Biggs et al, 2014; Ebmeier et al, 2018). The seismicity resulting from host rock fracturing can also be used to monitor the location and propagation of magma in the subsurface (McNutt & Roman, 2010; Smith et al, 2009; White et al, 2011).…”

An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

“…Magma intrusion induces crustal deformation, which in turn results in surface displacements, in changes in the local gravimetric field and in earthquake swarms, all of which can be monitored with geodetic and geophysical techniques (Brenguier et al, 2016;Fernández et al, 2017 and references therein; Figure 1A). Because direct observations of the intrusion emplacement are impractical, analytical, and numerical models are used to invert surface geodetic and/or geophysical monitoring data in order to constrain intrusion geometry and volume (Calais et al, 2008;Wauthier et al, 2012;Pinel et al, 2014;Sigmundsson et al, 2014;Fernández et al, 2017;Poland et al, 2017;Ebmeier et al, 2018). The most widely-used inverse geodetic models are limited by the simplifications and boundary conditions that are implemented to make mathematical solutions possible.…”