LAUSR

Based on the unscented Kalman filter, we develop a time‐dependent inversion filter combining Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) time series observations for modeling volcano deformation. We use the Variance Component Estimation method as means to assign the relative weights for GPS and InSAR data. Then we use the inversion filter to model the posteruptive deformation at Okmok volcano, Alaska. We find that a Mogi source at 3–4 km depth fits the InSAR data well, while the best fit to the GPS data is an oblate spheroid source at about 2.5 km depth. Our final model consists of a shallow sill at ~0.9 km and a Mogi source at ~3.2 km depth, which well fit both the GPS and InSAR data simultaneously. We think the Mogi source obtained here is the same source account for the preeruptive deformation. The shallow sill is a new structure that was not seen before the 2008 eruption. From 2008 to 2019, we have observed five inflation episodes, each of which decays exponential in time. We find that the characteristic timescale of those inflation episodes decreases with respect to time. The total volume change from the two sources is 0.068 km, which recovers 50–60% of the volume decrease during the 2008 eruption.