In Northwestern South America (NWSA) the geodetic data show a consistent northeastward displacement of blocks, while the geological record shows a predominant shortening in NW-SE direction suggesting a clear pattern of strain partitioning. This type of deformation has been extensively studied in the context of two convergent plates. However, in NWSA this is complicated by the interaction of multiple tectonic elements, including the Caribbean and Farallon/Nazca plates and the accretion of the Panama-Choco Arc. In this study we integrate the plate convergence evolution with multiple lines of evidence in the geological record, to propose a tectonic reconstruction that accounts for the deformation distribution during the Cenozoic. Our results indicate that deformation was not spatially homogeneous nor did it occur continuously during the Cenozoic. The main drivers of these variations were variations of convergence obliquity of the involved plates, the presence of heterogeneous lithospheric strength zones, changes in the geometry of the subducting slabs and the transition from subduction to collisional tectonics of the Panama-Choco Arc against NWSA. The obtained relative motion of blocks reproduces a strain evolution that is consistent with the different episodes of deformation reported in the literature. The model is additionally supported by the reconstructed velocity and strain vectors, which have a good match with equivalent indicators of the recent deformation in NWSA. Furthermore, the integration of the proposed palinspastic model with existing paleoenvironmental models, allowed us to construct restored paleogeographic maps that agree well with the deformation and exhumation history of the Northern Andes.

A sequence of three strong (M W 7.2, 6.4, 6.6) earthquakes struck the Pamir of Central Asia in 2015–2017. With a local seismic network, we recorded the succession of the fore-, main-, and aftershock sequences at local distances with good azimuthal coverage. We located 11,784 seismic events and determined 33 earthquake moment tensors. The seismicity delineates the tectonic structures of the Pamir in unprecedented detail, i.e., the thrusts that absorb shortening along the Pamir’s thrust front, and the strike-slip and normal faults that dissect the Pamir Plateau into a westward extruding block and a northward advancing block. Ruptures on the kinematically dissimilar faults were activated subsequently from the initial M W 7.2 Sarez event at times and distances that follow a diffusion equation. All mainshock areas but the initial one exhibited foreshock activity, which was not modulated by the occurrence of the earlier earthquakes. Modeling of the static Coulomb stress changes indicates that aftershock triggering occurred over distances of ≤90 km on favorably oriented faults. The third event in the sequence, the M W 6.6 Muji earthquake, ruptured despite its repeated stabilization through stress transfer in the order of -10 kPa. To explain the accumulation of M W > 6 earthquakes, we reason that the initial mainshock may have increased nearby fault permeability, and facilitated fluid migration into the mature fault zones, eventually triggering the later large earthquakes.

Using E-W and vertical deformation-rate maps derived from radar interferometric time-series, we analyze the deformation field of an entire orogenic segment, i.e., the Tajik depression and its adjoining mountain belts, Tian Shan, Pamir, and Hindu Kush. The data-base consists of 900+ radar scenes acquired over 2.0–4.5 years and global navigation satellite system measurements. The recent, supra-regional kinematics is visualized in an unprecedented spatio-temporal resolution. We confirm the westward collapse of the Pamir-Plateau crust, inverting the Tajik basin into a fold-thrust belt with shortening rates decaying westward from ~15 to 2 mm/yr. Vertical rates in the Hindu Kush likely record slab-dynamic effects, i.e., the progressive break-off of the Hindu Kush slab. At least 10 mm/yr of each, uplift and westward motion occur along the western edge of the Pamir Plateau, outlining the crustal-scale ramp along which the Pamir Plateau overrides the Tajik depression. The latter shows a combination of basin-scale tectonics, halokinesis, and seasonal/weather-driven near-surface effects. Abrupt ~6 mm/yr horizontal-rate changes occur across the kinematically-linked dextral Ilyak strike-slip fault, bounding the Tajik fold-thrust belt to the north, and the Babatag backthrust, the major thrust of the fold-thrust belt, located far west in the belt. The sharp rate decay across the Ilyak fault indicates a locking depth of ≤1 km. The Hoja Mumin salt fountain is spreading laterally at ≤350 mm/yr. On the first-order, the modern 20–5 and fossil (since ~12 Ma) 12–8 mm/yr shortening rates across the fold-thrust belt correspond.

Megathrust earthquakes impose changes of differential stress and pore pressure in the lithosphere-asthenosphere system that are transiently relaxed during the postseismic period primarily due to afterslip, viscoelastic and poroelastic processes. Especially during the early postseismic phase, however, the relative contribution of these processes to the observed surface deformation is unclear. To investigate this, we use geodetic data collected in the first 48 days following the 2010 Maule earthquake and a poro-viscoelastic forward model combined with an afterslip inversion. This model approach fits the geodetic data 14% better than a pure elastic model. Particularly near the region of maximum coseismic slip, the predicted surface poroelastic uplift pattern explains well the observations. If poroelasticity is neglected, the spatial afterslip distribution is locally altered by up to ±40%. Moreover, we find that shallow crustal aftershocks mostly occur in regions of increased postseismic pore-pressure changes, indicating that both processes might be mechanically coupled