Observing volcanic eruption dynamics from satellite radar intensity data
Dr Susanna Ebmeier (SEE), Dr Mike Poland (USGS), Prof Tim Wright (SEE)Project partner(s): CEOS Volcano Pilot projectContact email: firstname.lastname@example.org
Volcanic eruptions cause major changes to the topography and surface properties of the Earth that can be detected from space. This project will lead to advances in our ability to monitor the dynamics of ongoing eruptions using satellite data, by measuring changes in backscattered microwave radiation intensity caused by the emplacement of eruptive products. The volume, physical properties and temporal variability in the deposition of lavas, pyroclastic flows and ash are linked to conditions within the volcano and subsurface. For example, tracking individual lava flows provide insight into changes in magma supply rate through a conduit (e.g. Wadge et al., 2012) and observations of changes at the surface of a lava dome caused by high extrusion rates provides information about the ascent of magma (e.g., Goitom et al., 2015). Variations in backscattered radiation intensity can therefore provide information about the state of an erupting volcano, important for hazard assessment and forecasts.
The student will begin this project by examining the archive of high-resolution satellite radar imagery acquired over Kīlauea volcano, Hawai’i, as part of the Group on Earth Observations supersite programme (http://supersites.earthobservations.org/hawaii.php). This dataset spans both Kīlauea summit and Puʻu ʻŌʻō vents during extended periods of lava effusion and major transitions in the character of activity that resulted in significant changes to the Earth’s surface. The high density and quality of in situ and remote geophysical measurements at Kīlauea mean that long term magma supply rate and recent shallow magma dynamics have been well characterised (e.g., Anderson & Poland, 2016; Poland & Carbone, 2016). Kīlauea is therefore an ideal location to examine the potential of intensity data for linking surface intensity changes to the underlying subsurface processes.
Synthetic Aperture Radar (SAR) images capture the intensity of radiation backscattered from the Earth’s surface. After corrections to allow images with different geometries to be compared (e.g., radiometric terrain normalisation, Small, 2011), time series of the intensity of backscattered radiation may be constructed. These can be used to map ashfall, the emplacement of flows, and changes to lava domes during an eruption – particularly important for remote volcanoes with limited ground-based infrastructure. Simple ratio-based change detection (e.g., Ebmeier et al., 2014) can be improved upon by methods such as multiscale decomposition (Bovolo & Bruzzone, 2005) or automatic thresholding using Bayesian inference (e.g., Meyer et al., 2015) to reliably identify fresh eruption deposits. Information about the character of individual flow deposits (or about dome growth) can then be understood in terms of changes to surface roughness, and volumes estimated from radar shadow (e.g., Wadge et al., 2012; Arnold et al., 2016). Observations of transient stages of flow-field and dome growth are particularly valuable, as these are otherwise only obtainable at a few volcanoes worldwide where ground-based monitoring infrastructure is particularly extensive.
SAR has significant advantages for monitoring applications, especially as observations do not rely on cloud free conditions or solar radiation. However, such data have not yet been widely integrated into monitoring streams, in part due to high data costs. The usefulness of commercial radar intensity imagery for monitoring was shown during the 2010 eruption of Merapi, when rates of lava dome growth were estimated in near real time and used to forecast the development of the eruption (Pallister et al., 2013). The student will use the insights from the examination of archive imagery over Hawai’i to investigate the potential of the near-global, freely available Sentinel-1 SAR data for monitoring eruptions.
|Figure: Image of Kīlauea volcano, Hawai’i, USA from GoogleEarth. Both lava effusion on the Eastern Rift Zone from Puʻu ʻŌʻō vents and activity at the relatively young Halema’uma’u crater at the summit have produced topographic and surface property changes.|
The student will work with scientists in Leeds and at the United States Geological Survey (USGS) to investigate surface changes during volcanic unrest and eruption.
• The student will start by using archive SAR imagery over Kīlauea, Hawai’i to examine the potential of SAR intensity data for characterising eruption dynamics. This will involve developing novel tools using approaches such as change detection, time series of radar intensity or phase correlation and the integration of radar and optical satellite data.
As the student’s own research interests develop, further objectives could include multiple of:
• Using insights from research in Hawai’i to investigate lava flow dynamics using radar backscatter intensity at other, less thoroughly monitored volcanoes. Additional test cases will be selected in collaboration with the Centre for Earth Observations Satellite’s Volcano Pilot Project in Latin America, to allow comparison of various radar instruments and contribute to building remote sensing monitoring capacity in volcano observatories.
• Creating a module for the LICSAR processing software being developed at the University of Leeds capable of producing radiometrically calibrated intensity images useful for volcano monitoring. This would have the impact of making intensity data more accessible and useful for volcano observatories all around the world.
• Mapping land use change and variations in vegetation in response to volcanic activity during long-lived historical and ongoing eruptions. This may include the consequences of migration away from volcanic areas, the adaptation of infrastructure, or changes to agricultural practices.
Potential for high impact outcome
Analysis of SAR imagery, especially in combination with other remote sensing methods, has the potential to provide data not available from other sources, which is useful to volcanologists, civil protection authorities and disaster risk reduction practitioners. Publications arising from this project will be published in international journals, and are expected to result in high impact publications. A LiCSAR module that produces automatically generated SAR images suitable for change detection would potentially be widely used by the remote sensing community with broad interests in geohazards and other causes of land use change. It would also allow backscatter intensity observations to be made routinely at thousands of sub-aerial volcanoes around the world.
The student will work under the supervision of Dr Susanna Ebmeier in the Institute of Geophysics and Tectonics volcanology group, Dr Mike Poland at the USGS and Prof Tim Wright (tectonics group and head of COMET). The student will be trained in processing and analysing SAR intensity data from a range of historical and current satellites as well as measuring deformation and topographic change using interferometric methods. The student will be encouraged to expand their scientific horizons by participating in training programmes supported by international volcanological and geophysics networks such as IAVCEI and UNAVCO. The successful PhD student will have access to a broad spectrum of training workshops put on by the Faculty of the Environment at Leeds (http://www.emeskillstraining.leeds.ac.uk/).
The student should be interested in remote sensing and volcanic hazard assessment, have good quantitative data handling skills and be enthusiastic about learning and developing novel analysis methods. An interest in communicating scientific results and international collaboration is also desirable. The student should have a background in a quantitative science with some experience and interest in scientific computing.
• Anderson, K. R., & Poland, M. P. (2016). Bayesian estimation of magma supply, storage, and eruption rates using a multiphysical volcano model: Kīlauea Volcano, 2000–2012. Earth and Planetary Science Letters, 447, 161-171.
• Arnold, D. W. D., Biggs, J., Wadge, G., Ebmeier, S. K., Odbert, H. M., & Poland, M. P. (2016). Dome growth, collapse, and valley fill at Soufrière Hills Volcano, Montserrat, from 1995 to 2013: Contributions from satellite radar measurements of topographic change. Geosphere, GES01291-1.
• Bovolo, F., & Bruzzone, L. (2005). A detail-preserving scale-driven approach to change detection in multitemporal SAR images. IEEE Transactions on Geoscience and Remote Sensing, 43(12), 2963-2972.
• Ebmeier, S. K., Biggs, J., Muller, C., & Avard, G. (2014). Thin-skinned mass-wasting responsible for widespread deformation at Arenal volcano. Frontiers in Earth Science, 2, 35.
• Goitom, B, C. Oppenheimer, J. O. S. Hammond, R. Grandin, T. Barnie, A. Donovan, G. Ogubazghi et al. "First recorded eruption of Nabro volcano, Eritrea, 2011." Bulletin of volcanology 77, no. 10 (2015): 1-21.
• Meyer, F. J., McAlpin, D. B., Gong, W., Ajadi, O., Arko, S., Webley, P. W., & Dehn, J. (2015). Integrating SAR and derived products into operational volcano monitoring and decision support systems. ISPRS Journal of Photogrammetry and Remote Sensing, 100, 106-117.
• Pallister, J. S., D. J. Schneider, J. P. Griswold, R. H. Keeler, W. C. Burton, C. Noyles, C. G. Newhall, and A. Ratdomopurbo. "Merapi 2010 eruption—Chronology and extrusion rates monitored with satellite radar and used in eruption forecasting." Journal of Volcanology and Geothermal Research 261 (2013): 144-152.
• Poland, M. P., & Carbone, D. (2016). Insights into shallow magmatic processes at Kīlauea Volcano, Hawaiʻi, from a multiyear continuous gravity time series. Journal of Geophysical Research: Solid Earth, 121(7), 5477-5492.
• Small, D. (2011). Flattening gamma: Radiometric terrain correction for SAR imagery. IEEE Transactions on Geoscience and Remote Sensing, 49(8), 3081-3093.
• Wadge, G., Saunders, S., & Itikarai, I. (2012). Pulsatory andesite lava flow at Bagana Volcano. Geochemistry, Geophysics, Geosystems, 13(11).
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