Source parameters of the 2017Mw 6.2 Yukon earthquake doublet inferred from coseismic GPS and ALOS-2 deformation measurements

Abstract

We investigated an M w ∼ 6.2 earthquake doublet on the border of the USA and Canada using ALOS2 Light-of-Sight displacements and GPS measurements. We selected three L-band ALOS-2 interfergorams with temporal baselines of one yr to extract coseismic deformation maps, in which master and slave images were both acquired in July. A subpixel-based alignment and another range spectral splitting techniques under the GAMMA InSAR software framework were applied to improve the interferometric coherence and reduce the effects of phase anomalies in two of the three interferometric pairs due to either ionospheric delay or a potential focusing issues in the generation of the ALOS2 SLC data. The updated interferograms convincingly reveal deformation fringe patterns produced by the two earthquakes. We conducted a nonlinear geophysical inversion to estimate the geometric parameters of the earthquakes with the InSAR and GPS measurements. The best-fitting model shows that a thrust faulting on a reverse fault and left-lateral strike-slip faulting on a nearly vertical fault with the centroid depths of 9.3±0.6 and 8.4±0.7 km, respectively, are most likely responsible for the earthquake doublet. The eastern Denali fault (EDF) and Duke River fault are major active faults in the region and the earthquake doublet could be due to reactivation of the part of the two faults system.

Is the Eastern Denali fault still active?

“…Compared with previous investigations (He et al, 2018;Feng et al, 2019), novel aspects of our analysis included stress inversion, depth dependence of Coulomb stress change, detailed aftershock analysis (clustering), consideration of the regional geological context, and interpretation of changes in plate motion and tectonic history that produced the inferred stress regime. Our MT inversions confirm that the first mainshock was characterized by oblique-reverse slip on a west-dipping fault (based on aftershocks) with a significant non-double-couple (non-DC) component (∼40%).…”

“…2). Previous studies of the focal mechanisms of these events, as well as historical seismicity in the vicinity, reveal a mix of reverse and strike-slip faulting styles (Doser and Rodriguez, 2011;He et al, 2018;Feng et al, 2019). This sequence, herein named the St. Elias earthquake sequence, has been interpreted as reactivation of the Duke River fault, a southwest-dipping, terrane-bounding structure that runs subparallel to the EDF (He et al, 2018).…”

“…This sequence, herein named the St. Elias earthquake sequence, has been interpreted as reactivation of the Duke River fault, a southwest-dipping, terrane-bounding structure that runs subparallel to the EDF (He et al, 2018). Interferometric synthetic aperture radar (InSAR) and GPS data support the interpreted fault geometry (Feng et al, 2019), but the possibility of future activity on the EDF is unresolved, with important implications for earthquake hazards that could impact Whitehorse, Yukon, and Juneau, Alaska.…”

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

“…In this study, we used an improved multipeak particle swarm optimization (MPSO; Feng et al, , ; Feng, Lindsey, et al, ; Feng, Tian, et al, ; Feng et al, ) approach to invert nine source parameters, including the location of the center of fault upper edge, strike, dip, rake, slip, the depth of the fault upper edge, length, and width of the seismogenic fault. MPSO is a modified optimization algorithm based on Particle Swarm Optimization (PSO; Eberhart & Kennedy, ) for acquiring the global optimum result by simulating the movement of organisms in a bird flock, which also integrates a downhill simplex method to speed up the local searching processing to reduce total computational cost (Nelder & Mead, ).…”

“…After phase unwrapping, we geocode the interferograms to the geographic coordinates (WGS84). The atmospheric delay related to surface topography and a ramp were removed using a linear relationship between the DEM and the atmospheric signals, d los = a ⋅ DEM + b , where d los is the InSAR observations, a and b are the coefficients that are estimated from observations in the nondeformed area of far field (e.g., Feng et al, ; Wen et al, ). The wrapped phases in both ascending and descending tracks show clear fringe patterns corresponding to the earthquake rupture (Figure ).…”