Scientists studying Kaikoura tsunami need your help

Needles Point on the Marlborough coast that was raised by 2-3 m in the 7.8 earthquake. The gravel in the foreground and abundant seaweed is likely to have been washed up by the tsunami. Photo / GeoNet

Scientists are still trying to understand the strange tsunami activity that occurred in last month's 7.8 Kaikoura Earthquake - and have called upon people to help them.

Environment Canterbury geological hazard analyst Helen Jack said those who self-evacuated after the November 14 midnight quake "did the right thing".

"The earthquake triggered a tsunami and if it hadn't been for the substantial coastal uplift in many places, and the low tide at the time, it could have been much more damaging," she wrote in a GeoNet blog post.

Presently, the only report of the tsunami impacting property was water flooding 140m inland south of Kaikoura, badly damaging one home at Little Pigeon Bay.Residents of Sumner, Redcliffs, Port Levy and Pigeon Bay locals also reported tsunami waves striking the coast without causing damage.

The tsunamis hit different areas at different times on the morning of the quake, indicating the earthquake and aftershocks caused the waves.

However, there were numerous reports of the sea leaving seaweed, shellfish and fish stranded above high tide level, along with observations of the sea level falling below low tide, rising and falling quickly, and strange surges and currents.

"There is still a lot to untangle about what happened in the Kaikoura earthquake - 10faults that ruptured and still counting," Jack said.

The tsunami was an "important part" of the wider picture and GNS Science staff were collecting observations of the tsunami to help understand what happened in this event and what might happen in future events.

Sub-tidal shellfish found intact high on the beach near Needles Point. These are likely to have been washed up by the tsunami. Photo / GeoNet

The tsunami observations collected would be used in the New Zealand Tsunami Database entry related to this event and may be used to direct further fieldwork to investigate tsunami impacts.

"People's observations are also really important for us to improve our knowledge of tsunami impacts and to calibrate our tsunami models."

People who noticed unusual behaviour of the sea during the quake, or who saw items damaged by it, were asked to complete an online survey.