SATELLITE GEODETIC OBSERVATIONS OF THE COSEISMIC AND POSTSEISMIC DEFORMATION ASSOCIATED WITH THE 2010 MW 7.1 DARFIELD AND 2011 MW 6.3 CHRISTCHURCH EARTHQUAKES IN NEW ZEALAND

This paper investigates coseismic and postseismic deformation associated with the September 2010 Darfield and February 2011 Christchurch earthquakes in New Zealand using satellite geodetic observations. InSAR analyses of Envisat and ALOS are combined with high-quality campaign and continuous GPS data to constrain the rupture geometry and slip distribution of the 4 September 2010 Darfield earthquake. The inferred source model shows a very complex pattern involving rupture of multiple fault planes. The main rupture occurred on a previously unrecognized strike-slip Greendale Fault with as much as ~ 5 m of slip between depths of 3 and 8 km. A number of other faults were also active during this event including a northeast-striking blind reverse fault near Charing Cross, coincident with the earthquake hypocenter, and another blind reverse fault west of the Greendale fault near Hororata. TerraSAR-X InSAR observations of postseismic deformation shows shallow deformation on the Charing Cross reverse fault and a small amount of afterslip on the Greendale Fault. For the 22 February 2011 Christchurch earthquake, which is a large and late aftershock of the Darfield event, we utilized GPS together with X-band InSAR from Cosmo-Skymed and L-band InSAR from ALOS to investigate its source parameters. We find that the deformation pattern observed can be well explained by a slip on a single planar fault running into Christchurch city with a peak slip of ~ 2.5 m occurring at a depth of ~ 5 km. We report on postseismic deformation following this event analyzed by the integration of TerraSAR-X and GPS measurements.