In New Zealand we have a potential for very large earthquakes. This computer simulation
shows ground shaking or ground velocities during a potential magnitude 8.4 earthquake
on the plate boundary fault beneath the North Island of New Zealand.
Approximately two thousand times more energy would be
released than during the damaging magnitude 6.2 Christchurch earthquake in 2011.
In this scenario the segment of the plate boundary fault that
ruptures is at five to forty kilometres depth and is shown in the rectangle.
The earthquake rupture starts on the plate boundary fault
about sixteen kilometres beneath Waipukurau. It then moves towards Wellington
many other towns and rural communities would also be affected by a quake of this magnitude.
You can see that the model is running in real time.
The ground shaking is most intense towards the south
as this is the direction of photo rupture in this particular simulation.
Red indicates severe ground shaking with the highest level shown in yellow.
The ground shaking or peak ground velocity in this scenario is comparable to that
felt during the 6.2 February 2011 quake in Christchurch but lasts much longer -
one or two minutes rather than 10 seconds.
Severe shaking reaches Wellington
about a minute after the start of the earthquake.
The earthquake rupture terminates just south of Wellington in Cook Strait.
Shaking continues across the North Island and now also the South Island.
Geological and geodetic records suggest that an earthquake of this size
can occur on average every 500 to 1,000 years in the lower North Island.
The shaking would be felt severely throughout the lower half of the North Island
and the upper South Island.
Such an earthquake would cause extensive damage to New Zealand.
Very approximate losses can also be modeled: If the earthquake happened in day time
the estimates are in the range of 30 fatalities 900 injuries and 10 billion dollars
of direct losses to buildings but this estimation of losses does not include
those from subsequent events such as fires floods or tsunami.
Under this scenario tsunami would be generated due to displacement of the sea floor.
Here is a computer model of the tsunami which we'll show initially at x11 speed.
In the first two minutes the sea level rise is associated with the displacement of
the sea floor during the earthquake rupture. Then the tsunami waves begin to spread
in all directions. The scale bar does not show the maximum tsunami height
which would be between five and seven metres along the Wairarapa coast.
Note how quickly the tsunami travels. Within seven minutes after the
initial shaking the tsunami has already reached parts of the coast.
There would be no time for an official tsunami evacuation warning.
Finally we'll speed up our model again to show how the tsunami spreads along the coast
in the first hour following the earthquake.
The strength and duration of the earthquake shaking
would be the signal to immediately self evacuate all tsunami hazard zones
that is low-lying land in coastal areas.
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