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Wilkinson M.W.,Durham University | McCaffrey K.J.W.,Durham University | Roberts G.P.,Birkbeck, University of London | Cowie P.A.,University of Bergen | And 4 more authors.
Geophysical Journal International | Year: 2012

We captured post-seismic deformation close to the surface rupture of the 2009 L'Aquila earthquake (M6.3, central Italy) using repeat terrestrial laser scan (TLS) methods. From 8 to 126 d after the earthquake, we repeatedly laser scanned four road surfaces that intersected the earthquake surface rupture. We modelled vertical near-field deformation, at millimetre-level precision, by comparing subsequent laser scan data sets to the first acquired at each site. The horizontal post-seismic deformation at each site was measured between reflectors paired across the rupture. The TLS data were supplemented by total station data from a fifth site which measured the vertical and horizontal components of post-seismic deformation between two points spanning the rupture. We find post-seismic deformation increased between 44 and 126 d at the southeastern end of the rupture, beneath which a significant gradient in coseismic slip exists within the fault zone. The location, rate of decay and spatially-localized nature of the post-seismic deformation, within tens of metres of the surface rupture suggests it is due to afterslip in the fault zone, driven by increased shear stresses at the edges of regions which slipped coseismically. We note that the magnitude of post-seismic deformation in the far field obtained from InSAR and GPS is not significantly greater than the deformations we have measured close to the rupture. We suggest that shallow, localized afterslip within the fault zone is responsible for the majority of the regional post-seismic deformation field. © 2012 The Authors Geophysical Journal International © 2012 RAS.

Wilkinson M.,Durham University | McCaffrey K.J.W.,Durham University | Roberts G.,University of London | Cowie P.A.,University of Edinburgh | And 8 more authors.
Geophysical Research Letters | Year: 2010

Using 3D terrestrial laser scan (TLS) technology, we have recorded postseismic deformation on and adjacent to the surface rupture formed during the 6th April 2009 L'Aquila normal faulting earthquake (Mw 6.3). Using surface modeling techniques and repeated surveys 8-124 days after the earthquake, we have produced a 4D dataset of postseismic deformation across a 3 × 65 m area at high horizontal spatial resolution. We detected millimetre-scale movements partitioned between discrete surface rupture slip and development of a hangingwall syncline over 10's of meters. We interpret the results as the signal of shallow afterslip in the fault zone. We find 52% of the total postseismic hangingwall vertical motion occurs as deformation within 30 m of the surface rupture. The total postseismic vertical motions are approximately 50% that of the coseismic. We highlight the importance of quantifying partitioned postseismic contributions when applying empirical slip-magnitude datasets to infer palaeoearthquake magnitudes. Copyright © 2010 by the American Geophysical Union.

Guerrieri L.,High Institute for the Environmental Protection and Research | Baer G.,Geological Survey of Israel | Hamiel Y.,Geological Survey of Israel | Amit R.,Geological Survey of Israel | And 8 more authors.
Journal of Geophysical Research: Solid Earth | Year: 2010

On 6 April 2009, a moderate earthquake (Mw = 6.3; Ml = 5.8) struck the Abruzzo region in central Italy, causing more than 300 fatalities and heavy damage to L'Aquila and surrounding villages. Coseismic surface effects have been thoroughly documented by timely field surveys as well as by remote sensing analyses of satellite images. The outstanding quality of geological, seismological, geodetic, and interferometric synthetic aperture radar (InSAR) information arguably represents the best ever data set made available immediately after a moderate seismic event. Based on this data set, we aim at testing the capability of coupled geological and InSAR data to map surface faulting patterns associated with moderate earthquakes. Coseismic ground ruptures have been mapped at a scale of 1:500 in the whole epicentral area. Traces of surface ruptures have been inferred from linear phase discontinuities identified in the interferogram. A very good agreement between the two methods resulted in the characterization of the main surface rupture along the Paganica fault. The same approach applied to ground ruptures hypothesized along other capable fault segments provided more questionable results. Thus, the combined field and InSAR approach appeared useful for detecting continuous surface ruptures exceeding 1 km in length and showing displacements greater than a few centimeters. These are the typical faulting parameters for moderate earthquakes (6.0 < Mw < 6.5) in central Apennines. For continuous ground cracks shorter than a few hundred meters and/or that show displacements smaller than 1-2 cm, the described approach may be less helpful, most probably due to the limited resolution of the data. Copyright 2010 by the American Geophysical Union.

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