We propose to use space geodetic deformation and gravity data to study seasonal and long-term variations in deformation and seismicity in the southcentral alaska subduction zone. We will carefully…

This is a grant awarded by the National Aeronautics and Space Administration (NASA) to the University of California, Berkeley (UC Berkeley) to study the relationship between time-dependent surface loads, slow slip events, and seismicity in the south-central Alaska subduction zone. The grant, valued at $508,875.19, will support research using space geodetic deformation and gravity data to model the mechanical processes driving surface deformation and associated stress changes, and investigate how these changes correlate with seismicity patterns. The research aims to build on findings from similar studies in the western United States and India-Tibet collision zone. There is no set-aside designation for this award. As a public research university, UC Berkeley has received numerous federal contract and grant awards from agencies like NASA and the Department of Defense to conduct research across a range of scientific and technical domains.

We propose to use space geodetic deformation and gravity data to study seasonal and long-term variations in deformation and seismicity in the southcentral alaska subduction zone. We will carefully evaluate surface deformation, gravity changes and hydrological models to constrain mechanical models of time-dependent deformation and associated stress changes caused by hydrological loads. We will rigorously examine seismicity records for temporal variations that can be linked to the modeled time dependent stress changes. We will also study the time-variable deformation, stress changes and seismicity during recent slow slip events (SSES) in southcentral alaska. The results from this investigation will be compared and contrasted with related findings from the western U.S. And india-tibet collision zone, where we found evidence for correlated deformation and seismicity in response to time-dependent hydrological loads. To characterize the deformation resulting from the redistribution of surface loads, we will carefully extract and utilize both vertical and horizontal GPS time series including stations of the plate boundary observatory (PBO). The data will be inverted for the spatiotemporal evolution of surface loads on a layered elastic earth. The models will be further constrained by results from NASA S global land data assimilation system (GLDAS) and observations from the gravity recovery and climate experiment (GRACE). We will also examine the data for phase shifts between loads and deformation that can reflect contributions from viscoelastic relaxation and heterogeneous elastic earth structure. Earthquakes and seismicity rate changes reflect local stress conditions. Large-scale surface mass movements lead to time-dependent changes in local stress and therefore may promote or inhibit seismicity. We have recently discovered two seismicity patterns: (1) annual seismic variability and (2) a rate increase during a long-term SSE between 2008-2013. We will investigate the relationship of seasonal seismicity variation with the seasonal surface hydrologic mass loading changes in southcentral alaska. For the seismicity increase during long-term SSE periods, we will use the time-variable slip evolution during SSES inferred from continuous GPS measurements to model the spatiotemporal coulomb stress changes within the southcentral alaska subduction zone. We will focus on two recently discovered SSES and compare the modeled stress evolution with the observed spatio-temporal seismicity distribution and investigate the seismic triggering mechanism during the SSES. We will carefully explore the geodetic time series for additional slow slip episodes. We will rigorously test our results for possible biases from earthquake clustering, time-variable event detections and magnitude thresholds. We will apply a range of statistical tests to quantify the significance of inferred correlations between time-varying loads, surface deformation and seismicity.