CIFALPS & CIFALPS-2 projects : China-Italy-France Alps seismic survey

Duration : CIFALPS - 2012-2015. CIFALPS-2 - 2017-2020
Contact at ISTerre : Anne Paul
ISTerre research teams involved :

Summary

Seismic tomography data on the lithospheric structure of the western Alps (France-Italy) were surprisingly scarce, in strong contrast with structural geology and petrology data. Most crustal-scale models of the western Alps rely on the results of the ECORS-CROP controlled-source seismic experiments, which were located in the northernmost past of the French-Italian Alps. Local earthquake tomography and gravity modelling were later used to constrain the only crustal-scale model proposed for the southwestern Alps (Lardeaux et al., 2006). The geometry of the crust-mantle boundary was mostly extrapolated from the ECORS-CROP line recorded 150 km to the north. Moreover, the European Moho beneath the internal zone was not detected along the normal-incidence ECORS- CROP seismic line, and it could only be traced on wide-angle reflection data.

To get direct constraints on the Moho geometry of the southwestern Alps, we initiated the CIFALPS project (China-Italy-France Alps seismic survey ; 2012-2015), which was based on a temporary network of 55 broadband seismic stations installed for 14 months in 2012- 2013. The core of the CIFALPS experiment was a profile of 46 stations with an interstation spacing of 5 to 10 km. The profile trended WSW-ENE from Bollène (lower Rhône valley, France) to the region of Alessandria (Po plain, Italy), crossing the axial part of the range in the Monviso – Dora Maira region. The experiment was designed to optimize the quality of crustal tomography, using mainly receiver functions in a first step (Zhao et al., Geology 2015). Its data were also used together with those of permanent arrays for traveltime tomography of the mantle structure (Zhao et al., JGR-SE 2016), the study of anomalously deep earthquakes beneath the Po plain (Malusa et al. Gondwana Research 2017), surface-wave tomography of the mantle (Lyu et al., GJI, in review) and full-waveform inversion of teleseismic records (Beller et al., in review).

CIFALPS-2 is the direct continuation of CIFALPS. We will install 56 broadband seismic stations along a profile trending WNW-ESE in its western part (from the Mâcon region to the Aosta Valley) and NNW to SSE in its eastern part from the Aosta valley to the Genova region in the Ligurian Alps. We will pay a specific attention to the subduction complex in the Gran Paradiso Massif where we will install 2 additional lines parallel to the main one to increase the 2D coverage.

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Présentation du projet CIFALPS
Abstract EGU-2014 Paul et al.

(in English)