The BBC news article New Zealand quake: The geological impact of a 'complex' tremor says:
The powerful earthquakes which hit New Zealand were some of the most complex ever recorded, say scientists.
Most earthquakes are the result of rupture on a single fault plane. But the twin quakes led to the rupture of at least six faults, including a newly identified one at Waipapa Bay.
The article describes several resulting changes after the 7.8 magnitude 2016 Kaikoura earthquake, including seabeds raised above the surface, a dangerous 150m-high landslide dam has formed on the Hapuku River, and a town completely cut-off by landslides:
Kaikoura itself was completely cut off by landslides. About 1,000 tourists and locals have been evacuated by sea from the small town...
The image below is one of several from the article.
It's hard for me to understand what happened. It seems there were actually two distinct major earthquakes in rapid succession, and a lot of other motion and changes in nearby related faults. Was seismic data alone used to reach this conclusion, or is it a complex analysis of seismic, satellite, and ground-truth data used to "reconstruct" what actually happened? Is there some more technical description of the analysis available?