Post-seismic induced deformation after great earthquakes in the 21st century

Abstract:

Surface deformation after major earthquakes shows an ongoing transient signal known as post-seismic relaxation, which extends thousands of kilometers from the rupture area and continues in time for up to decades. The magnitude of this transient motion violates the secular/linear assumption made in current terrestrial reference frame definitions, which have significant ramifications for regional tectonic interpretations and global studies such as sea level rise that require reference frame accuracy greater than this level. In this study we show the importance of accounting for the post-seismic relaxation signal in GPS time series when defining a stable reference frame and estimating inter-seismic velocities. We investigate by means of long-term GPS time series analysis the far-field post-seismic effect of Sumatra Mw 9.1 and Macquarie Ridge Mw 8.1 earthquakes and show how deformation from great earthquakes can introduce a change in the long-term horizontal velocity rate of up to 5mm/yr. We show also how post-seismic deformation can affect regional tectonic interpretations and the detection of low strain fault zones in rapid rotating micro-plates. We highlight the role of post-seismic deformation on the characterization of the earthquake cycle as seen from long-term GPS time series.