Changes in Groundwater Level Possibly Encourage Shallow Earthquakes in Central Australia: The 2016 Petermann Ranges Earthquake

The mechanisms of unusual shallow intraplate earthquakes that occasionally occur in stable cratons remain poorly understood. Here we analyze coseismic and postseismic displacement fields associated with the 2016 Petermann Ranges earthquake in central Australia using interferometric synthetic aperture radar data. The earthquake ruptured a previously unmapped fault and was dominated by thrust slip motion of up to 95 cm within the top 3 km of the crust. Postseismic deformation analysis suggests that a combination of poroelastic rebound and afterslip are responsible for the observed signals. The inferred afterslip overlapping spatially with the coseismic rupture highlights that the postseismic slip is coupled with the pore fluid flow around the fault zones. Analysis of historic groundwater‐level changes suggests that shallow seismicity around the Petermann Ranges may have been triggered by environmental stress perturbations due to the fluctuations of groundwater level; however, it is not easy to document statistical significance of this correlation. Plain Language Summary Shallow surface‐rupturing earthquakes have been observed globally. However, how these events are triggered and why they sometimes occur within stable continents is largely unknown. We carefully study the coseismic and postseismic deformation of a 2016 Mw 6 earthquake in central Australia to determine the source parameters and slip distributions. We find the coseismic slip and early afterslip are concentrated at depths shallower than 3 km, and poroelastic rebound substantially contributes to the early period of postseismic deformation. We further investigate potential mechanisms to explain rock failure at such shallow depth and find a possible relationship between the fluctuations of groundwater level and the occurrence of shallow seismicity in the region. The results of this study help shed light on the processes and causes of shallow earthquakes.