Coseismic and Postseismic Deformation of the 2016 M-W 6.2 Lampa Earthquake, Southern Peru, Constrained by Interferometric Synthetic Aperture Radar

摘要

We use Sentinel-1 radar imagery to explore the coseismic and postseismic surface displacements associated with the 2016 M-W 6.2 Lampa earthquake in southern Peru. Based on coseismic interferograms, the preferred slip model links to a blind south southeast striking, south southwest dipping normal fault with a shallow dip (45.2 degrees) and a peak slip of 0.71m at depth 5.3km, which is consistent with seismic solutions. Postseismic interferograms, derived from two tracks of the Sentinel-1A/B satellites using a small baseline subset method, show subsidence up to 3cm in the first year after the mainshock. The kinematic inversions of interferometric synthetic aperture radar (InSAR) observations imply that the postseismic surface displacements observed in 1year after the earthquake are governed by afterslip occurring along the updip extension of the coseismic slip patches. To further improve the data fitting, we generate a fault with variable strike to refine the kinematic afterslip model. The stress-driven afterslip forward modeling shows that the postseismic deformation is controlled by afterslip distributed at the edge of the compact coseismic slip area. The surface displacement predictions of the poroelastic rebound show subsidence of the hanging wall, but the magnitude of the displacements is small compared to the observed signal. We as well test a collection of viscoelastic relaxation models and find that the predicted surface displacements are not consistent with the observations. The InSAR results show that the strike of the seismogenic fault is quasi-parallel to the Vilcanota normal fault system and both the fault associated with earthquake and Vilcanota normal fault dip in the same direction. Therefore, we suspect that the causative fault of this 2016 event may be a normal fault belonging to a domino faulting system.