09:15 〜 09:30
[G01-5-04] Restoring the New Zealand Geodetic Datum after the 2016 Kaikoura Earthquake
The 14 November 2016 magnitude 7.8 Kaikoura Earthquake and ensuing earthquake sequence resulted in widespread damage in the North Canterbury and Marlborough regions of the South Island of New Zealand. The earthquakes generated horizontal displacements of several metres and vertical displacements approaching 10 metres.
The deformation caused by these earthquakes needs to be incorporated in the New Zealand Geodetic Datum.
The datum includes a deformation model which accounts for both ongoing secular deformation and episodic earthquake related deformation. This enables a spatial reference system in which the coordinates of fixed ground marks are substantially constant over time despite the secular tectonic movement of the marks, thereby allowing the geospatial community to confidently combine and use spatial datasets from different epochs.
A challenge following earthquakes is to incorporate the resultant deformation into this datum in a timely way. Until this is done the datum does not provide a consistent spatial reference frame. Spatial data generated after the earthquake is likely to be out of terms with pre-earthquake data. Surveys conducted relative to local control marks may obtain significantly different coordinates depending on which marks are used.
The datum is updated using GNSS and InSAR data to derive models of the deformation caused by the earthquake sequence. Although the deformation model update is based on geophysical models of subsurface fault ruptures, the focus in building the model is to accurately reflect the surface deformation rather than accurately modelling the faulting.
The implementation of the model also needs to account for the needs and expectations of the geospatial community it serves. This may lead to different implementation methods in the near-field, where there is significant local relative movement, and in the intermediate and far field deformation, where the local deformation is predominantly translation.
The deformation caused by these earthquakes needs to be incorporated in the New Zealand Geodetic Datum.
The datum includes a deformation model which accounts for both ongoing secular deformation and episodic earthquake related deformation. This enables a spatial reference system in which the coordinates of fixed ground marks are substantially constant over time despite the secular tectonic movement of the marks, thereby allowing the geospatial community to confidently combine and use spatial datasets from different epochs.
A challenge following earthquakes is to incorporate the resultant deformation into this datum in a timely way. Until this is done the datum does not provide a consistent spatial reference frame. Spatial data generated after the earthquake is likely to be out of terms with pre-earthquake data. Surveys conducted relative to local control marks may obtain significantly different coordinates depending on which marks are used.
The datum is updated using GNSS and InSAR data to derive models of the deformation caused by the earthquake sequence. Although the deformation model update is based on geophysical models of subsurface fault ruptures, the focus in building the model is to accurately reflect the surface deformation rather than accurately modelling the faulting.
The implementation of the model also needs to account for the needs and expectations of the geospatial community it serves. This may lead to different implementation methods in the near-field, where there is significant local relative movement, and in the intermediate and far field deformation, where the local deformation is predominantly translation.