Locating distributed faulting: Contributions from InSAR imaging to Probabilistic Fault Displacement Hazard Analysis (PFDHA)

Earthquake-induced crustal deformation and consequences for fault displacement hazard analysis of nuclear power plants

“…Such a co-seismic deformation field, well imaged by remote sensing (i.e. InSAR data), is spatially correlated with DF also in areas far from the primary rupture (Livio et al, 2016), partially explaining an occurrence of DF more frequent than predicted from distance-based regressions. Earthquake-induced permanent strain can in fact result in the reactivation of pre-existing structures as compliant faults accommodating elastic deformation or in the promotion of new localized ground breaks.…”

“…It is clear that the total area affected by co-seismic deformation can be considered a good proxy for earthquake magnitude. Although focal depth and faulting type remain important parameters, they do not significantly affect the overall log-linear relationship of the regressed variables (Livio et al, 2016). (Youngs et al, 2003), (b) strike-slip faults (Petersen et al, 2011), and (c) reverse and strike-slip faults in Japan (Takao et al, 2013).…”

“…In particular, the predictive power of these models is challenged for areas far from the primary structure, where a higher occurrence of DF has been highlighted during recent earthquakes (e.g., the 2014 South Napa Valley earthquake, Mw 6.0, Baize and Scotti, 2015 and the 2009 L'Aquila earthquake, Mw 6.3, Livio et al, 2016). We suggest that some of the uncertainty has to be ascribed to deterministic factors commonly referred to as the geologic and stratigraphic setting of the faulted area (i.e., depth of the propagating fault, thickness of the brittle layer, fault geometry, basin architecture, etc.)…”

“…Fig. 2.10 (modified after Livio et al, 2016) shows the correlation between moment magnitude (Mw) and the area of co-seismic deformation as detected by InSAR. Areas of the deformed sectors located in both the hanging wall and in the footwall of the primary fault were measured.…”

“…Even if significant advances have been made for locating and mapping the primary fault, this task still remains problematic in the case of secondary ruptures and for distributed faults, (i.e., secondary or distributed faulting -DF) defined as ruptures that occur on faults in the proximity of a principal seismogenic structure, in response to the displacement on the primary fault (ANSI/ ANS-2.30, 2015). Present probabilistic approaches (e.g., Youngs et al, 2003;Petersen et al, 2011;Quittmeyer et al, submitted for publication) may underestimate the frequency of occurrence of secondary faults, especially far from the primary structure, as demonstrated by recent case studies (e.g., Napa Valley earthquake, Baize and Scotti, 2015; L'Aquila earthquake, Livio et al, 2016).…”