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Authors: Improta, L.* 
De Gori, P.* 
Chiarabba, C.* 
Title: New insights into crustal structure, Cenozoic magmatism, CO2 degassing and seismogenesis in the southern Apennines and Irpinia region from local earthquake tomography
Issue Date: 14-Nov-2014
Series/Report no.: /119 (2014)
DOI: 10.1002/2013JB010890
Keywords: The velocity structure of the southern Apennines is determined by a multi-scale tomography
Large Cenozoic mafic intrusions are identified in the Apulian crust
Pressurized CO2 reservoirs identified under the axial belt can affect crustal seismicity
Subject Classification04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous 
04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution 
04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics 
04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy 
04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics 
04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics 
04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks 
05. General::05.02. Data dissemination::05.02.01. Geochemical data 
05. General::05.02. Data dissemination::05.02.02. Seismological data 
Abstract: We present high-resolution Vp and Vp/Vs models of the southern Apennines (Italy) computed using local earthquakes recorded from 2006 to 2011 with a graded inversion scheme that progressively resolves the crustal structure, from the large scale of the Apennines belt to the local scale of the normal-fault system. High-Vp bodies defined in the upper and mid crust under the external Apennines are interpreted as extensive mafic intrusions revealing anorogenic magmatism episodes that broadened on the Adriatic domain during Paleogene. Under the mountain belt, a low-Vp region, annular to the Neapolitan volcanic district, indicates the existence of a thermal/fluid anomaly in the mid crust, coinciding with a shallow Moho and diffuse degassing of deeply derived CO2. In the belt axial zone, low Vp/Vs gas-pressurized rock volumes under the Apulian carbonates correlate to high heat flow, strong CO2-dominated gas emissions of mantle origin and shallow carbonate reservoirs with pressurized CO2 gas caps. We hypothesize that the pressurized fluid volumes located at the base of the active fault system influence the rupture process of large normal-faulting earthquakes, like the 1980 Mw6.9 Irpinia event, and that major asperities are confined within the high-Vp Apulian carbonates. This study confirms once more that pre-existing structures of the Pliocene Apulian belt controlled the rupture propagation during the Irpinia earthquake. The main shock broke a 30 km long, NE-dipping seismogenic structure, whereas delayed ruptures (both the 20 s and the 40 s sub-events) developed on antithetic faults, reactivating thrust faults located at the eastern edge of the Apulian belt.
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