Implementing Localised Deformation Models into a Semi-Dynamic Datum.

The New Zealand Geodetic Datum 2000 (NZGD2000) has an associated deformation model that allows horizontal coordinates to be reduced to a reference epoch of 2000.0 and is therefore a semi-dynamic datum. Currently, the deformation model does not account for either discrete or continuous horizontal deformation that can be associated with localised events such as earthquakes and landslides. Such events will distort the geodetic network by as little as a few millimetres a year, or as much as several metres in a matter of seconds. Using the August 2003 M 7.2 Fiordland earthquake as a case study, we demonstrate the implementation of a Localised Deformation Model (LDM) into the NZ National deformation model. LDMs employ triangulated interpolation techniques that predict surface displacement. In the Fiordland earthquake, eleven existing monitoring sites were resurveyed immediately following the earthquake and movements of up to 17 cm were observed. To model the associated co-seismic deformation, a LDM was generated from surface displacements predicted by a dislocation model of the earthquake. The LDM covered an area of approximately 56,000 km2. The implementation of a LDM into the NZGD2000 deformation model was successfully demonstrated. [ABSTRACT FROM AUTHOR]