Kinematic constraints on intra-arc shear and strain partitioning in the southern Andes between 38°S and 42°S latitude

[1] On the basis of structural field work, fault kinematic analysis, and the analysis of digital imagery, we describe the northern part of the southern Andean intra-arc Liquine-Ofqui Fault Zone (LOFZ) as an SC-like fault zone system accommodating part of the Nazca - South American plate convergence obliquity. Kinematic modeling suggests that the LOFZ accommodated 124 (+ 24/- 21) km of dextral displacement between 40 degrees S and 42 degrees S and 67 (+ 13/ -11) km between 38 degrees S and 40 degrees S since the Pliocene. Associated vertical axis rotations are 31 +/- 4 degrees clockwise and 9 +/- 1 degrees counterclockwise along synthetic and antithetic faults, respectively. Mean Pliocene to recent shear rates along the LOFZ decrease northward from 32 +/- 6 mm/ yr to 13 +/- 3 mm/ yr compatible with partitioning of half of the convergence obliquity into the intra-arc zone north of 40 degrees S and complete partitioning to the south. The displacement gradient along the intra-arc zone results in margin-parallel shortening of the fore arc.