Present‐day deformations of the Jura arc inferred by GPS surveying and earthquake focal mechanisms
Résumé
This study presents a compilation of more than 40 years of seismotectonic data, including 54 computed focal mechanisms, combined with 15 years of GPS data coming from a dense network of 35 permanent GPS stations within the Jura arc and its vicinity. These data are compared to previous available geomorphological, geophysical, and structural studies in order to discuss the 3D distribution of the deformation within the Jura arc. GPS data show coherent schemes in terms of velocities and allowed to discriminate between two provinces (NE of the belt and in its front/foreland). They also constrain a low but significant overall strain tensor with a NNW-SSE shortening of 2.16 nanostrain/year associated with an ENE-WSW extension of 0.44 nanostrain/year. The seismotectonic approach is based on a data set of 2,400 events and 54 focal mechanisms. Inversions of the focal mechanisms both globally and in homogeneous sectors highlight a general strike-slip deformation regime, with sigma1 oriented NW-SE and sigma3 oriented NE-SW. We discriminate two different sectors in terms of basement/cover (un)coupling: (1) potentially decoupled deformation between the basement and the sedimentary cover in the NE part; and (2) coupled deformation in the sedimentary cover and its basement in the Jura foreland.
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