Present-day geodynamics of the Western Alps: new insights from earthquake mechanisms

Abstract. Due to the low moderate seismicity of European Western Alps, few focal mechanisms are available in this region day, and corresponding current seismic stress strain fields remain partly elusive. The development dense networks past decades now provides a substantial number records 0–5 magnitude range. data, while challenging handle due their amount relative noise, represent new opportunity increase spatial resolution deformation fields. aim paper is quantitatively assess within from probabilistic standpoint, using seismotectonic data. dataset comprises more than 30 000 earthquakes recorded by between 1989 2013 2200 newly computed consistent manner. global distribution P T axis plunges confirms majority transcurrent entire western Alpine realm, combined with pure extension localized core belt. We inverted set through several strategies, including zoning scheme grid procedure, revealing extensional axes oriented obliquely strike Bayesian inversion continuous map style Alps. Extension found be clustered, instead continuous, along backbone Robust indications for compression only observed at boundary Adriatic Eurasian plates. Short-wavelength variations surface horizontal Global Navigation Satellite System (GNSS) measurements, as well deep lithospheric structures, thereby providing elements which understand 3D dynamics interpret ongoing kinematic regimes being controlled joint effects far-field forces – imposed anticlockwise rotation Adria respect Europe buoyancy belt, together explain short-wavelength patches marginal overprinted on an overall tectonic regime.