We present a new seismic tomography model for the crust and upper-mantle beneath the Central Andes based on multi-scale full seismic waveform inversion, proceeding from long periods (40–80 s) over several steps down to 12–60 s. The spatial resolution and trade- offs among inversion parameters are estimated through the multi-parameter point-spread functions. P and S wave velocity structures with a spatial resolution of 30–40 km for the upper mantle and 20 km for the crust could be resolved in the central study region. In our study, the subducting Nazca slab is clearly imaged in the upper mantle, with dip-angle variations from the north to the south. Bands of low velocities in the crust and mantle wedge indicate intense crustal partial melting and hydration of the mantle wedge beneath the frontal volcanic arc, respectively and they are linked to the vigorous dehydration from the subducting Nazca plate and intermediate depth seismicity within the slab. These low velocity bands are interrupted at 19.8-21° S, both in the crust and uppermost mantle, hinting at the lower extent of crustal partial melting and hydration of the mantle wedge. The variation of lithospheric high velocity anomalies below the backarc from North to South allows insight into the evolutionary foundering stages of the Central Andean margin. A high velocity layer beneath the southern Altiplano suggests underthrusting of the leading edge of the Brazilian Shield. In contrast, a steeply westward dipping high velocity block and low velocity lithospheric uppermost mantle beneath the southern Puna plateau hint at the ongoing lithospheric delamination.
This dataset includes video sequences depicting the evolution in map view and lateral view of 7 analogue experiments studying mantle-scale subduction systems. The experiments are performed under a natural gravity field and are designed to understand the role of convergence obliquity on upper plate deformation and partitioning, with a particular emphasis on the role played by lithospheric inherited structures on the development of sliver tectonics.
All experiments were performed at the Laboratory of Tectonic modelling of the University of Rennes 1 (France). The experimental set-up corresponds to a lithosphere and sub-lithospheric upper mantle system. The lithospheric plates are simulated with PDMS silicone (Polydimethylsiloxane Silicone) with different viscosities and densities, and the upper mantle with glucose syrup. In particular, for the overriding plate, we simulate the presence of a weaker volcanic arc that can eventually be decoupled from the forearc by a pre-existing discontinuity. The materials are placed into a Plexiglas tank, where the impermeable bottom of the tank represents the 660 km discontinuity. The subduction is initiated by manually forcing the slab into the mantle and it then evolves under the combined effects of internal buoyancy forces (slab pull) and external boundary forces. The subducting plate is pushed toward the trench at a constant velocity of 1.5 cm/min while the overriding plate is maintained fixed during the duration of the experiments.
The evolution of the experiments is monitored by DSLR cameras (24 Mpx) taking pictures every 30 seconds at the top and on one side of the experiments. Pictures are then assembled into video-sequences. The scale bar, with black & white rectangles corresponds to 10 cm.
The set of experiments consists of one reference model (MODEL-01) with orthogonal convergence, and six models with oblique convergence (Table 1). Among these models, three do not embed a pre-existing lithospheric discontinuity in the overriding plate (MODEL-02, MODEL-03, and MODEL-04) while the three other (MODEL-05, MODEL-06, and MODEL-07) have such a discontinuity. For the models with oblique convergence, we vary the angle between the convergence direction and the trench from 80° (MODEL-02 and MODEL-05) to 60° (MODEL-03 and MODEL-06) and 50° (MODEL-04 and MODEL-07).
For details on the experimental set-up, and interpretation of the results, please refer to Suárez et al. (submitted to Tectonophysics) to which these data are supplementary material.