The School of Earth and Atmospheric Sciences Presents Dr. Manoochehr Shirzaei, Arizona State University

SAR Interferometry and Applications in Hydrology and Induced Earthquake Forecasting

With the global population surpassing 7.7 billion people in 2019, the impacts of human activities on the environment are noticeable almost everywhere on our planet. The consequences of these impacts are still elusive, particularly when trying to quantify them at larger scales. 

It is essential to trace environmental changes from a local to global scale over several decades. This task is increasingly fulfilled by Earth observation (EO) satellites, in particular, radar imaging instruments. Synthetic Aperture Radar (SAR), a cloud-penetrant microwave imaging system, provides unique day-night and all-weather monitoring capabilities. 

Availability of repeated SAR acquisitions with similar imaging geometry allows performing interferometric SAR (InSAR) processing. InSAR uses radar to illuminate an area of the Earth’s surface and measures the change in distance between satellite and ground surface, as well as the returned signal strength. Such measurements are suitable for generating high-resolution digital elevation models and accurate terrain deformation maps.

Here, I will review some of the recent advances in developing modern multitemporal InSAR algorithms. 

Next, I present examples that demonstrate the value of high-resolution InSAR deformation maps in constraining the evolution of groundwater resources and crustal stress in Central Valley California as well as understanding the underlying mechanism that drives the injection-induced seismicity in Midwest US.  

We find that during 2007-2010 drought, a maximum subsidence rate of 20-25 cm/yr and 1-3 cm/yr occurred in the San Joaquin Valley and the Sacramento Valley, respectively. Using a 1-D poroelastic calculation, we find a loss of 21.3±7.2 km3 in the volume of groundwater across the Valley. We also inferred a permanent reduction of ~2% in aquifers-storage capacity.

Wastewater injection over the past decade has increased seismicity in the central USA, in some cases accompanied by detectable surface uplift. We show that the injection-induced uplift rate is controlled by the hydraulic diffusivity of the injection medium and thus we can use this uplift to constrain subsurface properties and pore pressure evolution. 

Hydraulic diffusivity determines the development of pore pressure and hence the origin and location of induced seismicity. We develop a physics-based forecasting model that integrates seismic, hydrogeologic and injection data to simulate the magnitude-time distribution of the M3+ earthquakes for the period of injection operation in Texas and Oklahoma.