Tsunami modelling with COMCOT and most other modelling software is based on a series of combined bathymetry and topography grids i.e. rectangular arrays of elevation/depth data, also called Digital Elevation Model (DEM) grids. These elevation modelling grids usually use Mean Sea Level as reference elevation level (zero elevation). These are prepared by processing and merging individual sources of elevation (e.g. LiDAR, topographic maps) and bathymetry (e.g. nautical charts, sonar) data into array grids. XYZ and ESRI ARC ASCII formats are two most commonly used data formats, compatible with most of GIS software. There are other proprietary formats for some simulation software. DOI: https://doi.org/10.21420/mhxg-7x67 Cite as: GNS Science. (2020). Elevation Modelling Grids [Data set]. GNS Science. https://doi.org/10.21420/MHXG-7X67

Tsunami propagation model outputs are snapshots of tsunami amplitude in a modelling domain at a given interval. The modelling domain for tsunami propagation includes the source region and the study area. Tsunami inundation model output show the simulated inland tsunami height and typically only for a limited area that is much smaller than the whole modelling domain. COMCOT is a tsunami simulation model used at GNS and by other parties to obtain tsunami propagation and inundation model output data. To get tsunami propagation model output, either linear or nonlinear shallow water equations can be use and a bathymetry data is needed. While to get tsunami inundation model output, COMCOT should be set to solve the nonlinear shallow water equations, and both topography and bathymetry data should be merged and then used in the simulation. Details of the specific procedures and outputs are usually provided in specific reports or papers for each project. DOI: https://doi.org/10.21420/747H-WJ91 Cite as: GNS Science. (2020). Tsunami Propagation and Inundation Model Outputs. GNS Science. https://doi.org/10.21420/747H-WJ91

On 5 March 2021, at 2.27 AM local time (4 March 2021, 13:27:34 UTC), a Mw 7.3 earthquake woke up the North Island of New Zealand with strong and long shaking. Its epicentre was located about 170 km NE offshore Gisborne in the Hikurangi subduction zone. This was the first tsunami of a triplet occurring on the same day. The tsunami propagated from the source region to the north shore of New Zealand, with a very localised and limited impact. Maximum amplitudes of ~32.3 cm and ~6.6 cm were respectively recorded at East Cape (LOTT) and North Cape (NCPT) coastal tsunami gauges, located ~105 km and ~660 km away from the epicentre. At 6.41 AM (17:41:23 UTC), 4 hours and 14 minutes later, another earthquake triggered a tsunami in the southwestern Pacific region with a magnitude Mw 7.4 earthquake. This was located further north (~ 900 km) than the previous one, 50 km south of Raoul Island (New Zealand) on the Kermadec subduction zone. At 8.28 AM (19:28:33 UTC), 1 hour and 47 minutes later, a Mw 8.1 earthquake occurred very close to the earlier Mw 7.4 earthquake, 80 km southeast of Raoul Island. It triggered a third tsunami that was recorded on New Zealand DART stations and coastal gauges, and all around the Pacific Ocean. Those data presents the arrival times and amplitudes of the first and third tsunamis on the New Zealand coastal gauges. DOI: https://doi.org/10.21420/P606-J332 Cite data as: GNS Science. (2021). Pacific Ocean sea-level records of the 5 March 2021 triplet of tsunamis [Data set]. GNS Science. https://doi.org/10.21420/P606-J332