- journal_title：Lithosphere
- Contributor：Claudio Chiarabba ; Pasquale De Gori ; Fabio Speranza
- Publisher：Geological Society of America
- Date：2009-
- Format：text/html
- Language：en
- Identifier：10.1130/L34.1
- journal_abbrev：Lithosphere
- issn：1941-8264
- volume：1
- issue：2
- firstpage：95
- section：RESEARCH
Data from high-density seismic networks deployed between 2000 and 2007 in the north-central Apennines (Italy) yield unprecedented images of an active orogenic wedge. Earthquake foci from the northern Apennines define a Benioff zone deepening westward from the Adriatic foreland down to ~60 km depth below the chain. The seismicity shows that only the lowermost ~10 km of the Adriatic foreland crust is subducted, whereas the uppermost ~20 km is incorporated into the orogenic wedge. Farther west, an aseismic mantle with markedly negative P-wave-velocity (Vp) anomalies is interpreted as asthenosphere flowing toward an Adriatic slab in retrograde motion. Three and seismicity characteristics are imaged below the northern Apennines: an uppermost 10-km-thick fast crustal layers with different Vp layer affected by extensional faulting, a slow layer with diffuse seismicity down to ~15 km depth, and a lowermost fast and aseismic layer resting directly above the asthenosphere. We interpret the latter layer as having formed by anhydrous crust undergoing granulitization, whereas trapped CO2 (either from the underlying granulites or from the subducting Adriatic crust) is inferred to have been responsible is released along the easternmost normal fault systems breaking for both low Vp and diffuse seismicity in the middle crust. Trapped CO2 the Apennine upper crust, consistent with geochemical and seismotectonic evidence. Compressive earthquakes at 20–25 km depth along the external front suggest offscraping of the subducting foreland crust and show that asthenospheric flow represents the primary source of ongoing shortening along the belt front.