Coseismic ground deformation of the 6 April 2009 L'Aquila earthquake (central Italy, M_w6.3)

Abstract

We provide field data of coseismic ground deformation related to the 6 April Mw 6.3 L'Aquila normal faulting earthquake. Three narrow fracture zones were mapped: Paganica‐Colle Enzano (P‐E), Mt. Castellano‐Mt. Stabiata (C‐S) and San Gregorio (SG). These zones define 13 km of surface ruptures that strike at 130–140°. We mapped four main types of ground deformation (free faces on bedrock fault scarps, faulting along synthetic splays and fissures with or without slip) that are probably due to the near‐surface lithology of the fault walls and the amount of slip that approached the surface coseismically. The P‐E and C‐S zones are characterized by downthrow to the SW (up to 10 cm) and opening (up to 12 cm), while the SG zone is characterized only by opening. Afterslip throw rates of 0.5–0.6 mm/day were measured along the Paganica fault, where paleoseismic evidence reveals recurring paleo‐earthquakes and post‐24.8 kyr slip‐rate ≥ 0.24 mm/yr.

On the complexity of surface ruptures during normal faulting earthquakes: excerpts from the 6 April 2009 L'Aquila (central Italy) earthquake (<i>M</i><sub>w</sub> 6.3)

“…Extensive albeit limited coseismic surface breaks were reported by several workers over a 100 km 2 region elongated in the NW-SE direction between L'Aquila and Monticchio, about 15 km to the southeast (see detailed descriptions in Boncio et al, 2010;the Emergeo Working Group, 2010, andVittori et al, 2011). The most continuous surface breaks were extensional cracks, some with a maximum net throw of a few centimeters, often seen at the top of a ∼ 10 m-high scarp formed by Quaternary continental deposits and running above the village of Paganica (Fig.…”

The anatomy of the 2009 L'Aquila normal fault system (central Italy) imaged by high resolution foreshock and aftershock locations

“…[33] We show in Figure 9 all of the relocated earthquakes, the active normal faults of the area [Boncio et al, 2010] and the location of the surface ruptures mapped soon after the main shock (yellow lines) [Boncio et al, 2010]. The main fractures border to the east the L'Aquila fault seismicity, along the Monte Stabiata (MSF) and Paganica-San Demetrio (PaF-SDF) geological faults.…”

“…For the 11 events with M W ≥ 4.4, whose earthquakes parameters are reported in Table 1, we adopt focal mechanisms solutions and moment magnitudes computed by Scognamiglio et al [2010], while for the active faults we use the catalog proposed by Boncio et al [2010]. The only exception in terms of moment magnitude is for the largest event occurred in the Cittareale cluster, M W 3.9.…”

“…[7] Evidence of surface breakage for 6-8 km of length was observed after the main shock [EMERGEO Working Group, 2009;Boncio et al, 2010] along the mapped Monte Stabiata and Paganica-San Demetrio faults. These features have been interpreted as a direct expression of fault rupture.…”

Evidence for strong middle Pleistocene earthquakes in the epicentral area of the 6 April 2009 L'Aquila seismic event from sediment paleofluidization and overconsolidation

“…A gravity minimum also Vezzani and Ghisetti, 1998], with location of the 6 April earthquake (black star). Thick fault segments were re-activated in 2009 [Boncio et al, 2010]. Coseismic interferogram fringes are from Lanari et al [2010].…”