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May 2013 - present
Publications
Publications (216)
Following two periods of dike intrusion in 2021 at Fagradalsfjall, Iceland, one of which led to an eruption, a third dike intrusion commenced on 30 July 2022. A sudden increase in seismicity occurred within the diking area, with approximately 1700 automatically detected earthquakes > M1 within 24 h. Strong earthquakes were felt over several days wi...
This paper presents the latest results obtained during the Phase A study of the Harmony mission for land applications. The contribution will focus on the performance of the 3-D deformation vectors (TDV) and topography change (TOC) products, for both solid Earth and land ice products, by using semi-analytical models and end-to-end simulations. Both...
Major strike-slip faults that develop between strong and weaker regions are thought to focus along narrow shear zones at the rheological boundary. Here we present the first InSAR-derived velocity field spanning almost the entire length of one such fault, the 1600 km-long Altyn Tagh Fault (ATF), and analyse the strain distribution. We find that loca...
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Here we report the first observation of unrest of the Socompa volcano, Northern Chile, which is thought to have last erupted thousands of years ago. Using radar interferometry technique and differencing radar images from two dates, it is possible to retrieve millimeter‐level surface displacements during this period. Here, we...
While satellite Persistent Scatterer SAR Interferometry (PSI) is an effective technique to monitor the health of structures via selection of long-term coherent pixels, detailed interpretation of displacement measurements requires knowledge of which surfaces, the reflection is coming from. Ray tracing algorithms can be used to simulate SAR backscatt...
Satellite-based earth observation sensors are increasingly able to monitor geophysical signals related to natural hazards, and many groups are working on rapid data acquisition, processing, and dissemination to data users with a wide range of expertise and goals. A particular challenge in the meaningful dissemination of Interferometric Synthetic Ap...
Increased rates of deformation and seismicity are well-established precursors to volcanic eruptions, and their interpretation forms the basis for eruption warnings worldwide. Rates of ground displacement and the number of earthquakes escalate before many eruptions1–3, as magma forces its way towards the surface. However, the pre-eruptive patterns o...
Monitoring large areas of the Earth's surface is possible thanks to the availability of remote sensing data obtained by a large collection of diverse satellites orbiting the Earth. Specifically, multitemporal interferometric synthetic aperture radar (MT-InSAR) techniques supply the structural community with time series of line-of-sight displacement...
Forecasting eruption is the ultimate challenge for volcanology. While there has been some success in forecasting eruptions hours to days beforehand, reliable forecasting on a longer timescale remains elusive. Here we show that magma inflow rate, derived from surface deformation, is an indicator of the probability of magma transfer towards the surfa...
Spatially-detailed maps of three-dimensional surface displacements and topography change, and their temporal evolution, are essential for understanding and modelling geophysical processes that trigger earthquakes, landslides and volcanic events, and for the assessment of hazards arising from these phenomena. Current SAR missions are sensitive to ve...
Harmony was one of the three missions that was selected as ESA Earth Explorer 10 mission candidates. After a down-selection process at the end of the Phase-0 studies, Harmony, proceeded as the only remaining candidate to a Phase-A, which will close in the summer 2022. This presentation gives an overview of the mission, reflecting its current status...
After decades of oil, gas, and coal exploitation, we have learned about some of the unpleasant aftereffects of subsurface resource exploration. Adverse long-term impacts, some known during exploration periods, others only afterwards, may include induced seismicity, land subsidence, or even sinkholes. While geothermal is currently seen as a sustaina...
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Earthquakes cause the ground to temporarily shake, but also result in permanent movement of the surface of the Earth. This surface displacement can be detected using sensitive radar echoes from satellites when it is large enough. By differencing phases of radar images from before and after the earthquake (a technique known as...
We numerically assess the effectiveness of the equivalent medium (EM) theory for discrete fracture network (DFN) models by means of seismic waveforms. More specifically, we analyse how the discrete crack parameters, such as crack density, crack stiffness, and crack size, influence the effective properties of a cracked medium by utilising the stocha...
Improvement of our understanding of the role of ground deformation due to viscoelastic relaxation following eruptions is important, as the generated signals can resemble renewed magma inflow. We study post‐eruptive unrest at the subglacial Bárðarbunga volcano, Iceland, after a caldera collapse and major magma drainage in 2014–2015. Elevated seismic...
Space-borne Synthetic Aperture Radar (SAR) Interferometry (InSAR) is now a key geophysical tool for surface deformation studies. The European Commission’s Sentinel-1 Constellation began acquiring data systematically in late 2014. The data, which are free and open access, have global coverage at moderate resolution with a 6 or 12-day revisit, enabli...
On January 22, 2020, inflation of 3-4 mm per day started in the volcanic system of Svartsengi, within 5 km of several important infrastructure: a) the town of Grindavík (pop. 3300); b) the Svartsengi geothermal power plant, 75MWe, 150 MWth; c) and the Blue Lagoon geothermal spa, which has over 1 million annual visits. Grindavík is one of two towns...
Large volume effusive eruptions with relatively minor observed precursory signals are at odds with widely used models to interpret volcano deformation. Here we propose a new modelling framework that resolves this discrepancy by accounting for magma buoyancy, viscoelastic crustal properties, and sustained magma channels. At low magma accumulation ra...
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Unrest at Bárðarbunga after a caldera collapse in 2014-2015 includes elevated seismicity beginning about six months after the eruption ended, including nine Mw>4.5 earthquakes. The earthquakes occurred mostly on the northern and southern parts of a caldera ring fault. Global Navigation Satellite System (GNSS, in particular, Global Position...
We present a new procedure and program system to integrate Sentinel-1 synthetic aperture radar (SAR) interferometry and Global Navigation Satellite System (GNSS) network observations to estimate 3-D surface changes caused by environmental processes. The procedure is based on the integrated geodetic/geodynamic benchmarks, which are equipped with bot...
The geometry and frictional properties of a fault system are key parameters required to understand its seismic behavior. The Main Himalayan Thrust in Nepal is the type example of a continental megathrust and forms part of a fault system which accommodates a significant fraction of India‐Eurasia convergence. Despite extensive study of this zone of s...
Cerro Azul is one of the most active volcanoes in the western Galápagos Islands, but its unrest episodes are poorly studied. Unrest, which started in 2007, culminated in two eruptive phases from 29 May to 11 June 2008. We investigate this unrest and the associated eruptions using interferometric synthetic aperture radar (InSAR) data and geodetic mo...
For the past five years, the 2-satellite Sentinel-1 constellation has provided abundant and useful Synthetic Aperture Radar (SAR) data, which have the potential to reveal global ground surface deformation at high spatial and temporal resolutions. However, for most users, fully exploiting the large amount of associated data is challenging, especiall...
Cerro Azul is one of the most active volcanoes in the western Galápagos Islands, but its unrest episodes are poorly studied. Here unrest, which started in 2007, culminated in two eruptive phases from May 29th to June 11th 2008.We investigate this unrest and the associated eruptions using interferometric synthetic aperture radar (InSAR) data and geo...
The 2011–2014 volcanic activity at El Hierro (Canary Islands) was characterized by a 5‐month long submarine eruption as well as a series of magmatic intrusions occurring between 5 months and 2 years after the eruption, as revealed by seismic swarms and ground deformation. We study the temporal evolution of the six post‐eruptive magmatic intrusions,...
The final stage of continental break-up is often accompanied by abundant magmatism. Erta 'Ale volcano lies on the Nubia-Arabia extensional boundary in Afar, Ethiopia, an incipient mid-ocean ridge. A fissure on the south flank of Erta 'Ale began erupting on 21 January 2017 and has remained active until at least July 2019. We use Sentinel-1 synthetic...
The latest generation of SAR satellites produce measurements of ground deformation at the majority of the world's sub‐aerial active volcanoes, and can be used to detect signs of volcanic unrest. We present an automatic detection algorithm that uses these data to automatically warn when deformation at a volcano departs from the background. We demons...
The final stage of continental break-up is often accompanied by abundant magmatism. Erta 'Ale volcano lies on the Nubia-Arabia extensional boundary in Afar, Ethiopia, an incipient mid-ocean ridge. A fissure on the south flank of Erta 'Ale began erupting on 21 January 2017 and has remained active until at least July 2019. We use Sentinel-1 synthetic...
There are potentially dangerous areas where InSAR technology cannot be applied routinely in the absence of proper persistent or distributed scatterers. Here, we planned and investigated the use of truncated trihedral triangle corner reflectors (CRs) oriented to ascending and descending directions for Sentinel-1 orbit, which were mounted on the opti...
Understanding the physical properties of fractures, location, orientation, and geometry is of primary importance in the comprehension of geo-resources and geo-hazards. In doing so seismic waves can be an effective tool for non-invasive investigation of fracture parameters. We have developed a novel stochastic Full Waveform Fracture Inversion employ...
Analogue and numerical models show that strong or weak domains in a deforming ductile material cause stress concentrations that may promote strain localization. Such domains commonly occur in the lithosphere through variations in composition or mineral fabric. Here we use a 2D plane-stress, non-Newtonian, viscous model to explore how strain localiz...
Understanding volcanic unrest is crucial to forecasting eruptions. At active mafic calderas, unrest usually culminates in eruption, and does so more frequently than at felsic calderas. However, the mafic caldera of Alcedo Volcano (Ecuador) has experienced repeated episodes of unrest without erupting, since at least 1992, when geodetic monitoring be...
Variation in tropospheric delay is a major limiting factor on the accuracy of interferometric synthetic aperture radar (InSAR) measurements. This is particularly the case when deformation and topography are correlated. To address limitations of previous InSAR tropospheric correction methods, here we present a new approach that combines the use of b...
Understanding volcanic unrest is crucial to forecasting eruptions. At active mafic calderas
unrest culminates in eruption more frequently than at felsic calderas. However, the mafic caldera of
Alcedo Volcano (Ecuador) has experienced repeated episodes of unrest without erupting, since at least 1992,
when geodetic monitoring began. Here we investiga...
Many earthquake properties, including slip, show self-similar (fractal) features. We can incorporate self-similarity into Bayesian slip inversions via von Karman correlation, so that the regularization applied is representative of observed fault features. In von Karman regularization, each slip patch has a relationship to every other patch. This me...
Torfajökull volcano, Iceland, has not erupted since 1477. However, intense geothermal activity, deformation, and seismicity suggest a long-lasting magmatic system. In this paper, we use ambient noise tomography to image the magmatic system beneath Torfajökull volcano. One hundred days of ambient noise data from 23 broadband seismometers show the co...
Land subsidence in urban environments is an increasingly prominent aspect in the monitoring and maintenance of urban infrastructures. In this study we update the subsidence information over Rome and its surroundings (already the subject of past research with other sensors) for the first time using Copernicus Sentinel-1 data and open source tools. W...
We report how data from satellite and aerial synthetic aperture radar (SAR) observations were integrated into monitoring of the 2014–2015 Holuhraun eruption in the Bárðarbunga volcanic system, the largest effusive eruption in Iceland since the 1783–84 Laki eruption. A lava field formed in one of the most remote areas in Iceland, after the propagati...
There are some 1,500 volcanoes with the potential to erupt, but most are not instrumentally monitored. However, routine acquisition by the Sentinel‐1 satellites now fulfils the requirements needed for interferometric synthetic aperture radar (InSAR) to progress from a retrospective analysis tool to one used for near‐real‐time monitoring globally. H...
Ground deformation in utilized geothermal areas is often attributed either to pressure decrease or temperature decrease in the geothermal reservoir. A new geothermal power plant at Reykjanes began operation in May 2006 and local deformation caused by geothermal utilization was observed shortly thereafter. We use images acquired by the Envisat and T...
We processed InSAR time series of ENVISAT ASAR descending and ascending datasets and identified two new deforming areas on the northern shore of Lake Kivu, characterized by steady ground subsidence of up to ~1 cm/year over a time period of about seven years (December 2002/January 2003–March 2010). Two distinct areas can be identified: one centered...
Sentinel-1 represents a major step forward in enabling us to monitor the Earth's hazardous tectonic and volcanic zones. Here, we present the latest progress from the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET), where we provide deformation results to the community for volcanoes and the tectonic belts. Fo...
New satellite missions (e.g., the European Space Agency's Sentinel-1 constellation), advances in data downlinking, and rapid product generation now provide us with the ability to access space-geodetic data within hours of their acquisition. To truly take advantage of this opportunity, we need to be able to interpret geodetic data in a prompt and ro...
While polarimetric persistent scatterer InSAR (PSI) is an effective technique for increasing the number and quality of selected PS pixels, existing methods are suboptimal; a polarimetric channel combination is selected for each pixel based either on amplitude, which works well only for high-amplitude scatterers such as man-made structures, or on th...
Distributions of coseismic slip help illuminate many properties of earthquakes, including fault geometry, stress changes, frictional properties, and potential future hazard. Slip inversions take observations and calculate slip at depth, but there are a number of commonly adopted assumptions such as minimizing the second spatial derivative of slip (...
The interferometric coherence is a measure of the correlation between two SAR images and constitutes a commonly used estimator of the phase quality. Its estimation requires a spatial average within a 2-D window, usually named as multilook. The multilook processing allows reducing noise at the expenses of a resolution loss. In this letter, we analyz...
Combining persistent scatterers (PS) and distributed scatterers (DS) is important for effective displacement monitoring using time-series of SAR data. However, for large stacks of synthetic aperture radar (SAR) data, the DS analysis using existing algorithms becomes a time-consuming process. Moreover, the whole procedure of DS selection should be r...
Induced seismicity is often associated with fluid injection but only rarely linked to surface deformation. We observed both at the Hellisheidi geothermal power plant in SW Iceland.
We identify flaws in the criticisms of Harning et al. (2018).
Earthquakes are caused by the release of tectonic strain accumulated between events. Recent advances in satellite geodesy mean we can now measure this interseismic strain accumulation with a high degree of accuracy. But it remains unclear how to interpret short-term geodetic observations, measured over decades, when estimating the seismic hazard of...
Induced seismicity is often associated with fluid injection but only rarely linked to surface deformation. At the Hellisheidi geothermal power plant in south-west Iceland we observe up to 2 cm of surface displacements during 2011–2012, indicating expansion of the crust. The displacements occurred at the same time as a strong increase in seismicity...
The two weeklong rifting event at Bárðarbunga volcano in 2014 led to the Holuhraun eruption, which produced 1.5 km3 of lava and was the largest in Iceland in over 200 years. Predicting when and where an intrusion will lead to eruption requires detailed knowledge of the underlying stress field. Previous studies have explained the dike propagation pa...
Human-induced climate change is causing rapid melting of ice in many volcanically active regions. Over glacial-interglacial time scales changes in surface loading exerted by large variations in glacier size affect the rates of volcanic activity. Numerical models suggest that smaller changes in ice volume over shorter time scales may also influence...
Over 14 days propagating seismicity and deformation revealed the onset of a rifting event with the formation of a 47 km-long segmented dyke extending from subglacial Bárðarbunga caldera to the Holuhraun plain, located ~10 km north of the Vatnajökull ice cap in Iceland. A major effusive eruption started on 31 August 2014 and lasted about 6 months, p...
Multitemporal polarimetric synthetic aperture radar (SAR) data can be used to estimate the dominant scattering mechanism of targets in a stack of SAR data and to improve the performance of SAR interferometric methods for deformation studies. In this letter, we developed a polarimetric form of amplitude difference dispersion (ADD) criterion for time...
The two-satellite Copernicus Sentinel-1 (S1) constellation became operational in Sep 2016, with the successful in-orbit commissioning of the S1B unit. During, the commissioning phase and early operational phase it has been confirmed that the interferometric performance of the constellation is excellent, with no observed phase anomalies. In this wor...
Stress transfer associated with an earthquake, which may result in the seismic triggering of aftershocks (earthquake–earthquake interactions) and/or increased volcanic activity (earthquake–volcano interactions), is a well-documented phenomenon. However limited studies have been undertaken concerning volcanic triggering of activity at neighbouring v...
After > 200 years of quiescence, in July 2011 an intense seismic swarm was detected beneath the center of El Hierro Island (Canary Islands), culminating on 10 October 2011 in a submarine eruption, 2 km off the southern coast. Although the eruption officially ended on 5 March 2012, magmatic activity continued in the area. From June 2012 to March 201...
Differential Interferometric SAR (DInSAR) time-series techniques can be used to derive surface displacement rates with accuracies of 1 mm/year, by measuring the one-dimensional distance change between a satellite and the surface over time. However, the slanted direction of the measurements complicates interpretation of the signal, especially in reg...
The North Anatolian Fault (NAF) is a major tectonic feature in the Middle-East and is the most active fault in Turkey. The central portion of the NAF is a region of GNSS scarcity. Previous studies of interseismic deformation have focused on the aseismic creep near the town of Ismetpasa using radar data acquired in a single line-of-sight direction,...
We investigate crustal deformation due to the extraction of water and steam from a high-enthalpy geothermal reservoir; a common occurrence, yet not well understood. The cause of this deformation can be a change in pressure or in temperature in the reservoir, both of which can be caused by extraction or injection of geothermal fluids. Our study area...