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SUMMARY:Unravelling the complexity of the geometry and nucleation phase of
  Apennininc extensional systems: the case of the 2009  MW 6.1 L’Aquila n
 ormal fault system (Central Italy). - Lauro Chiaraluce\, Istituto Nazional
 e di Geofisica e Vulcanologia\, Rome
DTSTART:20111115T163000Z
DTEND:20111115T173000Z
UID:TALK32057@talks.cam.ac.uk
CONTACT:John Maclennan
DESCRIPTION:In 2009\, a MW 6.1 normal faulting earthquake struck the axial
  area of the Abruzzo region in Central Italy. We analysed the continuous r
 ecordings of the very dense seismic network composed by 60 stations that o
 perated in the epicentral area for 9 months by integrating an accurate aut
 omatic picking procedure together with cross-correlation and double-differ
 ence relative location methods. The adopted procedure allowed us to recove
 r an extraordinary set of data composed by high-precision locations for 64
 000 earthquakes. Events span in magnitude (ML) between -0.9 to 5.9\, reach
 ing a completeness magnitude of 0.7.\nFor the first time the geometry of t
 he faults at depth imaged by seismicity distribution (seismological faults
 ) highly resemble from the kilometer to meter scale\, the geometry of the 
 outcropping faults mapped on the field (geological faults). These data wil
 l help us to improve our knowledge about: a)  how faults behave at the sur
 face\; b) how crustal faults 'end' at depth\; c) what the transition from 
 brittle to ductile crust looks like and d) how stress gets distributed at 
 the transition.\nWe also inverted P‐ and S‐wave travel times to infer 
 the velocity structure in the crustal volume where the April 6th main shoc
 k nucleated to image local variations of P‐wave velocity and Poisson rat
 io along the fault zone. The interpretation of the complex initial stages 
 of the mainshock rupture and the spatial variations of VP and Poisson rati
 o once again points to a strong correlation between material properties an
 d presence of fluids in the source volume.\nFinally\, we focus on the anal
 ysis of about 300 clusters of repeating earthquakes characterising the mec
 hanical behaviour of secondary fault segments structures often not optimal
 ly oriented with the crustal stress field.\n\n\n\nReferences.\n\nThe anato
 my of the 2009 L’Aquila normal fault system [Central Italy] imaged by hi
 gh resolution foreshock and aftershock locations. L. Chiaraluce\, L. Valor
 oso\,  D. Piccinini\, R. Di Stefano and P. De Gori (In press on JGR).\n\nD
 i Stefano\, R.\, C. Chiarabba\, L. Chiaraluce\, M. Cocco\, P. De Gori\, D.
  Piccinini\, and L. Valoroso (2011)\, Fault zone properties affecting the 
 rupture evolution of the 2009 (Mw 6.1) L’Aquila earthquake (central Ital
 y): Insights from seismic tomography\, Geophys. Res. Lett.\, 38\, L10310\,
  doi:10.1029/2011GL047365.
LOCATION:Harker 1 seminar room\, Department of Earth Sciences
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