The 2009 L'Aquila (central Italy) MW6.3 earthquake: Main shock and aftershocks

[1] A M w 6.3 earthquake struck on April 6, 2009 the Abruzzi region (central Italy) producing vast damage in the L'Aquila town and surroundings. In this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks. The distribution of aftershocks, 712 selected events with M L > 2.3 and 20 with M L > 4.0, defines a complex, 40 km long, NW trending extensional structure. The main shock fault segment extends for 15―18 km and dips at 45° to the SW, between 10 and 2 km depth. The extent of aftershocks coincides with the surface trace of the Paganica fault, a poorly known normal fault that, after the event, has been quoted to accommodate the extension of the area. We observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes.

[1]  A. Michetti,et al.  Spatial and temporal variations in growth rates along active normal fault systems: an example from The Lazio–Abruzzo Apennines, central Italy , 2004 .

[2]  G. Lavecchia,et al.  Defining a model of 3D seismogenic sources for Seismic Hazard Assessment applications: The case of central Apennines (Italy) , 2004 .

[3]  Roberto Scarpa,et al.  Inversion of source parameters from near‐ and far‐field observations: An application to the 1915 Fucino earthquake, central Apennines, Italy , 1998 .

[4]  C. Collettini,et al.  Connecting seismically active normal faults with Quaternary geological structures in a complex extensional environment: The Colfiorito 1997 case history (northern Apennines, Italy) , 2005 .

[5]  M. Ripepe,et al.  Complex Normal Faulting in the Apennines Thrust-and-Fold Belt: The 1997 Seismic Sequence in Central Italy , 2004 .

[6]  Gianluca Valensise,et al.  Faulting mechanism and complexity of the November 23, 1980, Campania-Lucania Earthquake, inferred from surface observations , 1990 .

[7]  P. Galli,et al.  Active Tectonics in the Central Apennines (Italy) – Input Data for Seismic Hazard Assessment , 2000 .

[8]  Christian Bignami,et al.  Finite fault inversion of DInSAR coseismic displacement of the 2009 L'Aquila earthquake (central Italy) , 2009 .

[9]  Alessandro Maria Michetti,et al.  Fault scarps and deformation rates in Lazio–Abruzzo, Central Italy: Comparison between geological fault slip-rate and GPS data , 2005 .

[10]  Maurizio Ripepe,et al.  The 1997 Umbria‐Marche, Italy, Earthquake Sequence: A first look at the main shocks and aftershocks , 1998 .

[11]  J. Lahr.  HYPOELLIPSE; a computer program for determining local earthquake hypocentral parameters, magnitude, and first-motion pattern , 1979 .

[12]  Romano Camassi,et al.  Rapporto sugli effetti del terremoto aquilano del 6 aprile 2009 , 2009 .

[13]  D. Pantosti,et al.  Paleoseismicity of the Ovindoli‐Pezza fault, central Apennines, Italy: A history including a large, previously unrecorded earthquake in the Middle Ages (860–1300 A.D.) , 1996 .

[14]  Alessandro Maria Michetti,et al.  Sintesi delle conoscenze sulle faglie attive in Italia Centrale: parametrizzazione ai fini della caratterizzazione della pericolosità sismica , 2000 .

[15]  Nicola D'Agostino,et al.  Active tectonics of the Adriatic region from GPS and earthquake slip vectors , 2008 .

[16]  M. Romanelli,et al.  Background seismicity in the Central Apennines of Italy: The Abruzzo region case study , 2007 .

[17]  Claudio Chiarabba,et al.  A new view of Italian seismicity using 20 years of instrumental recordings , 2005 .

[18]  Alessandro Amato,et al.  Performance of the INGV National Seismic Network from 1997 to 2007 , 2008 .

[19]  G. Luca,et al.  Seismicity in Central and Northern Apennines integrating the Italian national and regional networks , 2009 .

[20]  Luca Malagnini,et al.  Effect of time-dependence on probabilistic seismic hazard maps and deaggregation for the central apennines, Italy , 2009 .

[21]  F. Galadini,et al.  New paleoseismological data from the Gran Sasso d'Italia area (central Apennines) , 2002 .