Reassessing the Rupture Process of the 2009 L’Aquila Earthquake (M_w 6.3) on the Paganica Fault and Investigating the Possibility of Coseismic Motion on Secondary Faults

Abstract

The kinematic rupture of the L'Aquila earthquake on the Paganica fault is reassessed with a highly comprehensive set of data. This very complete dataset is also used to explore the possibility that secondary faults may be involved in the coseismic process. The main characteristics of the slip distribution of the Paganica normal fault found by previous studies are confirmed: an initial propagation around and up-dip of the hypocenter, associated with a high velocity rupture (> 3:5 km=s); a main asperity centered about 6-7 km southeast of the hypocenter, rupturing in the subsequent stage, with a maximum slip of nearly 1.5 m; a total rupture measuring about 15 km along strike and 12 km along dip; and an overall low average velocity rupture (< 2 km=s). The statement that the main features of the slip distribution are confirmed by different studies (based on distinct inversion schemes) is by itself an achievement, knowing that many past studies provided strongly discrepant slip maps for common events. Moreover, we focus specifically on the existence of slip at shallow depth and its relations with the other known active faults in the vicinity of the Paganica fault. We find that (1) as found in previous studies, shallow slip near the ground surface up-dip of the hypocenter is incompatible with the available Synthetic Aperture Radar interferograms and (2) the only secondary fault that is likely to have been activated during the mainshock is the San Gregorio synthetic fault located 2-3 km southwest of the Paganica fault.Online Material: Figures of waveform fitting using different velocity models, time versus distance distribution of slip from the single-fault model, variations in the geometry of the Paganica fault, geometry of complex faults models and geodetic data modeling, uncertainty on the slip value and the rupture time, effect of noise on resolution tests, quantification of the improvement on the GPS data fitting with the preferred two faults model with respect to the single-fault model, and a posteriori modeling of leveling data.

Coseismic Stress and Strain Field Changes Investigation Through 3‐D Finite Element Modeling of DInSAR and GPS Measurements and Geological/Seismological Data: The L'Aquila (Italy) 2009 Earthquake Case Study

“…The DInSAR measurements have been subsampled with the Quadtree algorithm (Jonsson et al, ) for the ascending and the descending interferograms to produce a set of about 8,000 and 11,000 points, respectively, suitable for the optimization procedure. Regarding the GPS measurements, we consider 13 stations localized in the near‐deformation field, consistently with the previous analysis presented by Balestra and Delouis () and Cheloni et al ().…”

“…This moderate intra‐Apennine earthquake has been already investigated from the geological and seismological point of view (Chiaraluce et al, ; Lavecchia et al, ) and from the kinematic aspects through analytical and numerical models (Atzori et al, ; Cheloni et al, , ; Chiaraluce et al, ; Cirella et al, ; Lanari et al, ; Serpelloniet al, ; Trasatti et al, ; Walters et al, ). Most commonly, the AQE seismogenic main fault geometry and the related slip distribution have been analyzed by considering single or multiple planar source models and by assuming a homogeneous, isotropic, and elastic upper crust (Atzori et al, , ; Balestra & Delouis, ; Cheloni et al, ; Dalla Via et al, ; Guerrieri et al, ; Guglielmino et al, ; Walters et al, ). According to the analytic model solutions, a maximum coseismic slip of 75–100 cm has been estimated beneath the ruptured Paganica Fault System (PFS) trace, but the results relevant to the retrieved depth of the slip concentration are highly variable, with a mean value of about 6 km (Atzori et al, ; Cheloni et al, ; Cirella et al, ; Gualandi et al, ; Serpelloni et al, ; Trasatti et al, ).…”

Joint Inversion of Coseismic and Early Postseismic Slip to Optimize the Information Content in Geodetic Data: Application to the 2009 Mw6.3 L'Aquila Earthquake, Central Italy

“…(), and Cirella et al. () (inferred respectively from GPS only, from accelerometric and high rate GPS data, and from GPS, InSAR, and strong motion; see Figure ) and most of other authors (Atzori et al., ; Balestra & Delouis, ; Cheloni et al., ; D'Agostino et al., ; Serpelloni et al., ; Trasatti et al., ; Volpe et al., ). It is the only recurrent pattern we can notice between the four slip models of Figure .…”

“…The mainshock nucleated on the Paganica fault (Figure ; Atzori et al., ; Cheloni et al., ; Chiaraluce et al., ; Falcucci et al., ; Lavecchia et al., ; Vittori et al., ), southwest of the city of L'Aquila, and has been followed by at least four aftershocks of M w >5 (Chiarabba et al., ; Pondrelli et al., ; Scognamiglio et al., ). Although the L'Aquila earthquake has been intensively studied, most coseismic and postseismic models have considered the first days of postseismic deformation as if they were part of the coseismic phase (e.g., Anzidei et al., ; Atzori et al., ; Balestra & Delouis, ; Cheloni et al., , ; Cirella et al., ; D'Agostino et al., ; Trasatti et al., ; Volpe et al., ). To avoid the contamination of coseismic signal by early afterslip, Yano et al.…”

Joint inversion of co-seismic and early post-seismic slip: Application to the 2009 Mw6.3 LAquila earthquake, Central Italy

“…[2014], Gallovic et al [2015] and Cirella et al [2012] (inferred respectively from GPS only, from accelerometric and high rate GPS data, and from GPS, InSAR and strong motion, see Figure 8) and most of other authors [Atzori et al, 2009;Trasatti et al, 2011;D'Agostino et al, 2012;Serpelloni et al, 2012;Cheloni et al, 2014;Balestra and Delouis, 2015;Volpe et al, 2015]. It is the only recurrent pattern we can notice between the 4 slip models of Figure 8.…”