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

Abstract

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°) and a peak slip of 0.71 m at depth~5.3 km, 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~3 cm 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 1 year 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.

Volcano-tectonic interactions at Sabancaya volcano, Peru: eruptions, magmatic inflation, moderate earthquakes, and fault creep

“…After an initial period of afterslip, creep on this fault continues linearly, in tandem with the continuing inflation ( Figures 8 and 10). Although long-lived afterslip on a normal fault is not unprecedented in this tectonic setting, the longest recorded afterslip in this region lasted for only one year [Xu et al, 2019], far less than the 5+ years of creep observed in this study. For the Hayward fault in California, Schmidt and Bürgmann [2008] found that, after an earthquake, creep resumed when the ratio of shear to normal stress matched the value of this ratio prior to the earthquake.…”

Volcano‐Tectonic Interactions at Sabancaya Volcano, Peru: Eruptions, Magmatic Inflation, Moderate Earthquakes, and Fault Creep

“…After an initial period of afterslip, creep on this fault continues linearly, in tandem with the continuing inflation (Figures and ). Although long‐lived afterslip on a normal fault is not unprecedented in this tectonic setting, the longest recorded afterslip in this region lasted for only 1 year (Xu et al, ), far less than the 5+ years of creep observed in this study. For the Hayward fault in California, Schmidt and Bürgmann () found that, after an earthquake, creep resumed when the ratio of shear to normal stress matched the value of this ratio prior to the earthquake.…”

Numerical Insight Into Energy Partitioning During Stick‐Slip Events Based on the Framework of Rate‐and‐State Friction Law

“…This postseismic behavior shares features similar to many experimental results (Chambon et al., 2006; Cornelio et al., 2019; Jia et al., 2020; Nielsen, Spagnuolo, Violay, et al., 2016; Ohnaka & Shen, 1999). Postseismic slip (or deformation) also has been widely reported in natural earthquakes, for example (Hussain et al., 2018; Lin et al., 2013; Perfettini & Avouac, 2004; Twardzik et al., 2019; Xu et al., 2019). Due to the different slip weakening behavior, Type I events show smaller breakdown slip displacement than Type II events (10 vs. 15 μm; Figure S8a in Supporting Information ).…”