Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/6064
AuthorsPasquale, G.* 
De Matteis, R.* 
Romeo, A.* 
Maresca, R.* 
TitleEarthquake focal mechanisms and stress inversion in the Irpinia Region (southern Italy)
Issue Date2009
Series/Report no./13 (2009)
DOI10.1007/s10950-008-9119-x
URIhttp://hdl.handle.net/2122/6064
KeywordsIrpinia Region
Seismicity
Focal mechanisms
Stress inversion
Subject Classification04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics 
04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress 
04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics 
AbstractThe goal of this study was to estimate the stress field acting in the Irpinia Region, an area of southern Italy that has been struck in the past by destructive earthquakes and that is now characterized by low to moderate seismicity. The dataset are records of 2,352 aftershocks following the last strong event: the 23 November 1980 earthquake (M 6.9). The earthquakes were recorded at seven seismic stations, on average, and have been located using a three-dimensional (3D) P-wave velocity model and a probabilistic, non-linear, global search technique. The use of a 3D velocity model yielded amore stable estimation of take-off angles, a crucial parameter for focal mechanism computation. The earthquake focal mechanisms were computed from the P-wave first-motion polarity data using the FPFIT algorithm. Fault plane solutions show mostly normal component faulting (pure normal fault and normal fault with a strikeslip component). Only some fault plane solutions show strike-slip and reverse faulting. The stress field is estimated using the method proposed by Michael (J Geophys Res 92:357–368, 1987a) by inverting selected focal mechanisms, and the results show that the Irpinia Region is subjected to a NE–SW extension with horizontal σ3 (plunge 0◦, trend 230◦) and subvertical σ1 (plunge 80◦, trend 320◦), in agreement with the results derived from other stress indicators.
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