Frequency‐Dependent Rupture Characteristics of the 30 October 2016 Mw 6.5 Norcia, Italy Earthquake Inferred From Joint Multi‐Scale Slip Inversion

Abstract

AbstractThe relationship between multi‐scale rupture characteristics and different frequency contents of the seismic waveforms has been revealed for moderate to great earthquakes by previous researches. To better understand such a relationship, we propose a two‐step strategy to perform finite fault inversion in the wavelet domain with multi seismic datasets, involving the seismic observations at both teleseismic and near‐field distances. In our two‐step strategy, the larger‐scale pattern of the seismic rupture is first constrained by using the lower‐frequency seismic waveforms and then based on the lower‐frequency rupture pattern, the higher‐frequency rupture features are obtained by performing inversion with higher‐frequency data. We apply this two‐step strategy with multi seismic datasets to study the 30 October 2016 Mw 6.5 Norcia, Italy earthquake, which is the largest event of the 2016–2017 central Italy seismic sequence. By analyzing the recovered slip patterns from different frequency bands, we notice the frequency‐dependent rupture features of this earthquake. The lower‐frequency slip concentrated at the shallower depths above the source, and the higher‐frequency slip appeared near the edges of the lower‐frequency slip patch, working as “barriers”, due to fault complexities in central Italy. The frequency‐dependent slip pattern of the 30 October 2016 Norcia earthquake shows a relation to the unevenly distributed pore fluid pressure, as indicated by Vp/Vs tomography from previous researches. Our results suggest that fault complexities and unevenly distributed fluids contribute to the frequency‐dependent rupture of this earthquake.