IMAGING OF SLOW-SLIP TRANSIENTS ON FAULTS BY UNSCENTED KALMAN FILTER

Aseismic slip can have a strong influence on the moment budget of faults which needs to be quantified for accurate seismic hazard estimates. Aseismic slip also redistributes stress in the crust affecting the locations of future earthquakes. In some studies, it has been demonstrated that slow-slip events have the potential to trigger occurrence of destructive earthquakes. So detailed imaging of aseismic fault-slip events plays a significant role in seismotectonic and seismic hazard studies.There are major challenges in developing inverse methods that can determine detailed information about the space-time variations in the aseismic slip-rate on faults from geodetic data. Because of the contaminating effects of multiple contributing signals such as fault-slip, local benchmark motion and measurement errors; interpretation of the displacement time-series resulting from these events is not straightforward.In the literature, time dependent inversion algorithm based on the Extended Kalman Filter (EKF) has been introduced as a common inverse method for geodetic data. This method can separate the various signals and allow the space-time evolution of slow-slip transients to be studied in detail.It has been shown that EKF has a few serious drawbacks, which should be considered when it is applied. For instance, the linear and quadratic transformation produces reliable results only when the error propagation can be well approximated by a linear or a quadratic function. As a result, if this condition is not met, the performance of the filter can be extremely poor.In this paper, Unscented Kalman filter (UKF) has been applied. This filter has the capability to overcome the mentioned drawbacks by employing Unscented Transform (UT). In a companion paper (Unscented kalman filter based inversion of geodetic data; submitted in this volume), we applied UKF to the simple problem of uniform slip and slip-rate on the fault. In that paper we claimed that for problems in which nonlinearity is more complex, for example nonuniform slip rate, performance of UKF-based filter will be more obvious. This paper is going to address the imaging of nonuniform slip and slip-rate on faults through simulation data set.