Estimation of the rupture directivity and source parameters of moderate magnitude earthquakes using the second moment tensors

Understanding how ruptures propagate and seismic source parameters, including seismic moment, rupture magnitude, and stress drop, is critical to studying earthquake source dynamics and understanding the physics of the earthquake phenomenon. While rupture directivity is traditionally associated with highmagnitude earthquakes, it can also play an important role in moderate earthquakes, leading to unexpected and severe damage. Therefore, estimating the directivity in near real-time during an earthquake would be a valuable contribution to seismic risk assessment and emergency management in this work, we first reviewed existing methods in the literature to evaluate their advantages and limitations for near real-time applications. We then focused on a method based on second seismic moments that has demonstrated successful to retrieve both the directivity and source parameters of small to moderate earthquakes. To evaluate the robustness of this method, we used a bootstrap approach to assess the impact of uncertainties in our input data on the results. In addition, we investigated an experimental method based on frequency domain analysis, aiming to extend the applicability of the existing time-domain based method to low signal-to-noise ratios data. Some study cases on real data recorded for earthquakes in Central Italy are presented. The are promising and indicate the potential for further research to improve and refine this method. To enable near-real time application of this method is our perspective for future work