Abstract
After large earthquakes, parts of the fault continue to slip for days to months during the afterslip phase, a behaviour documented for many earthquakes. Yet, little is known about the early stage, i.e., from minutes to hours after the mainshock. Its detailed study requires continuous high-rate position time series close to the fault, and advanced signal processing to accurately extract the surface displacements. Here, we use refined kinematic precise point positioning processing to document the early postseismic deformation for three earthquakes along the South American subduction zone (2010 Mw8.8 Maule, Chile; 2015 Mw8.3 Illapel, Chile; 2016 Mw7.6 Pedernales, Ecuador). First, we show that early afterslip generates significant surface displacement as early as a few tens of minutes after the earthquake. Our analysis of the time series indicates that, over the first 36 hours, more than half of the displacement occurs within the first 12 hours, a time window often disregarded with daily positioning. Thus, estimates of coseismic offsets can be biased by more than 10% if early postseismic displacements are acknowledged as coseismic ones. Finally, these results highlight the difficulty to accurately evaluate the different contribution to the seismic cycle budget and thus the associated hazard on faults.
Highlights
The postseismic phase marks the transition between the earthquake coseismic rupture and the interseismic phase, when the fault is re-locking
Before analysing our observations with a focus on the postseismic phase only, we have first attempted to quantify the impact of early postseismic surface displacements on the estimation of coseismic offsets, a question often raised during the retrieval of coseismic slip distributions using geodetic data e.g
First, we provide a detailed analysis on the emergence of postseismic surface displacement in high-rate kinematic position time series for three subduction zone earthquakes
Summary
The postseismic phase marks the transition between the earthquake coseismic rupture and the interseismic phase, when the fault is re-locking. This is pointed out by Helmstetter and Shaw[19], who have extended the comparison to the rate-and-state friction law under velocity-strengthening (i.e., stable aseismic slip) and velocity-weakening (i.e., unstable slip) regime, the rate-dependent friction law, and an empirical law based on the observed time decay of aftershocks This discrepancy at the early stage of the postseismic phase has been explained based on a theoretical approach[20]. Langbein et al.[21] are among the first to investigate the early postseismic phase They used sub-daily GNSS position time series at 13 sites, with variable positioning intervals (1-minute, 3-minute, and 30-minute) to capture the time evolution of surface displacement after the 2004 Parkfield earthquake, as early as 100 seconds and up to 10 days after the mainshock. Early afterslip might not necessarily scale with the magnitude of the mainshock, as observed at the time scale of a few months[27]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
