My research focuses on understanding the processes that govern natural and anthropogenic hazards. These studies incorporate large quantities of remote sensing data such as space-based differential interferometric synthetic aperture radar (DInSAR), GPS data, seismicity and gravity, in order provide insights into the nature and scale of these hazards. Specific projects focus on improvements in the quality of those data, development of innovative analysis techniques and assimilation into geophysical models of the underlying processes. As part of that effort we investigate the implications and consequences of hazards such as earthquakes, volcanoes, landslides, groundwater extraction, and induced seismicity on infrastructure and society.
In one of several induced seismicity projects I collaborate on, we identified the first frack-induced earthquakes in North America. Induced seismicity is largely caused by the disposal of wastewater produced during oil and gas operations. Up until this work, the direct triggering of events by fracking itself was considered rare or even nonexistent. This result provides new insights into the mechanisms surrounding induced seismicity.
Campi Flegrei caldera is one of the most hazardous volcanic areas in the world because of its close proximity to the city of Naples, a city of approximately 3 million people where almost 1 million people live within the caldera itself. We are applying advanced DInSAR time series analysis at Campi Flegrei and obtained vertical and horizontal components of ground deformation at unprecedented spatial and temporal resolutions over a 20-year time period. Although the area underwent continuous slow subsidence from 1993 through 1999, moderate uplift began in 2010 and substantially increased through 2012, reaching approximately 13 cm by 2013, suggesting that new magma injected at shallow depths presents increased risk to the local and regional population. We also modeled the observed deformation to determine magma depth and volume for both the subsidence and uplift epochs. Both the inflation and deflation mechanisms involve large, extended sources in a layered hydrothermal system whose location is controlled by the caldera structure and stratigraphy (Tiampo et al., 2017).
Improved DInSAR Using High-Resolution Topography
The nearly global coverage of the Shuttle Radar Topography Mission (SRTM) DEMs significantly simplified and improved the modelling and removal of topography for differential interferometric synthetic aperture radar (DInSAR) applications. Today, the TanDEM-X mission produces DEMs at higher resolutions on a global basis. Here we generate an improved DEM using a stack average of 39 DEMs produced from TanDEM-X bistatic interferometric pairs over Tenerife Island, Spain. We demonstrate the improvements on computed differential interferograms and coherence maps provided by the high-resolution DEM. The incorporation of the higher resolution DEM into the DInSAR processing improves the differential phase and coherence quality by significantly reducing the geometric decorrelation. The improvement is greater for large spatial baselines, which expands the range of potentially useful interferometric image pairs for deformation applications (McKee et al., submitted, 2019).