Resolving Teleseismic Earthquake Catalog and InSAR Data Discrepancies in Absolute Space to Explore Rupture Complexity Along the Ecuadorian Megathrust Fault

Abstract

AbstractThe 2016 MW 7.8 Pedernales, Ecuador, megathrust earthquake produced notable crustal deformation and generated an extensive aftershock sequence that included two M6.5+ events. We combine an improved teleseismic earthquake catalog for Ecuador with analysis of coseismic interferometric synthetic aperture radar data derived from the Sentinel‐1A satellite to better delineate the spatial and temporal slip history of the megathrust fault in absolute space. The revised teleseismic catalog spans 1961‐2016 and incorporates catalog phase onset times and waveform correlation derived differential times to locate earthquakes. Using teleseismic double‐difference (DD) tomography to simultaneously solve for an updated regional 3‐D compressional velocity model and locations yields earthquakes shifted ~25 km southwest relative to rapidly available teleseismic catalogs. The DD catalog better compares in absolute space to the Ecuadorian local catalog and better models the measured deformation fields of the 2016 Pedernales mainshock and largest aftershocks. Additionally, the DD mainshock location agrees with local‐scale seismic and geodetic studies that show the 2016 event had concentrated slip on a highly coupled asperity that likely participated in the 1942 Ecuador megathrust earthquake. The two large aftershocks also ruptured on the megathrust where moderate to strong interseismic coupling is observed. The DD catalog contains moderate‐sized aftershocks that concentrate outside high slip regions, primarily in areas that produced earthquakes during the interseismic cycle, and outside areas of aseismic slip. Development of rapid relative location approaches linking new seismicity to better constrained global catalogs could aid with near real‐time hazard assessment in areas lacking local data.