Deep Transient Slow Slip Detected by Survey GPS in the Region of Atacama, Chile

Abstract

We detected a long‐term transient deformation signal between 2014 and 2016 in the Atacama region (Chile) using survey Global Positioning System (GPS) observations. Over an ∼150 km along‐strike region, survey GPS measurements in 2014 and 2016 deviate significantly from the interseismic trend estimated using previous observations. This deviation from steady state deformation is spatially coherent and reveals a horizontal westward diverging motion of several centimeters, along with a significant uplift. It is confirmed by continuous measurements of recently installed GPS stations. We discard instrumental, hydrological, oceanic, or atmospheric loading effects and show that the transient is likely due to deep slow slip in the transition zone of the subduction interface (∼40‐ to 60‐km depth). In addition, daily observations recorded by a continuous GPS station operating between 2002 and 2015 highlight similar transient signals in 2005 and 2009, suggesting a recurrent pattern.

Dynamically Triggered Changes of Plate Interface Coupling in Southern Cascadia

“…The closest analogue to the Mendocino case was observed south of the Iquique earthquake in Chile, where interface coupling appeared to increase after the earthquake on a distant enough part of the plate interface to preclude static triggering (Hoffmann et al, ). Several other changes in megathrust coupling have been observed in Chile and are potentially also associated with earthquakes (Jara et al, ; Klein et al, ; Melnick et al, ). Transients in GNSS velocities in northeast Japan have also been documented and suggested to reflect coupling changes, although they may represent a different process (Heki & Mitsui, ; Mavrommatis et al, ).…”

Source and pattern identification of ground deformation based on the framework of Blind Source Separation--Nonnegative Matrix Factorization: a case study in a long-term GPS monitoring mine

“…Most of sudden disasters are evolved from a long-time slow and micro deformation and the location of final failure always controlled by the previously deformed belts. GPS has successfully applied to detect the slow slip and micro deformation of landslides and mining induced ground deformation (Gourmelen et al 2007;Klein et al 2018;LI Xiao 2020). Prediction of deformation is the main issue in previous studies (Chen et al 2020) .…”

Kinematics of Slow-Slip Events

“…In Chile, along a megathrust fault off northernmost Chile, where the Nazca plate subducts beneath the South American plate, a long-term slow-slip event occurred in a transition zone at depth of 40-60 km with the following kinematic values: S = 50-80 cm, T = 240, L = 70-150 km, W = 20-30 km, and M = 6.5-6.9. Also a short-term event indicated by earthquake migration occurred with S = 1.3-8 cm, T = 2-15 days, L = 20-60 km, W = 20-30 km, and M = 6.5-6.7 [11,[106][107][108]. Table 1 gives a summary of the estimated kinematic values of slip S, duration T, rupture length L, rupture width W, and magnitude M, as well as calculated values of slip velocity V S = S/T, rupture velocity V R = L/T, and S/L, which is a measure of stress drop.…”