Building structures experienced by severe earthquake attack should be carefully inspected to identify their condition status - they can either be continuously and safely functioned or strengthening/rehabilitation activities should be put in place. This reflects the increasing need of structural health monitoring, under the environment of more frequent natural disasters.

On the other aspect, buildings may be exposed to multiple hazards including earthquake, fire, progressive collapse and post-earthquake fire. Multiple hazards are low-frequency but high-consequence events, thus multi-hazard resilience is of a strong demand for critically-important building and infrastructure facilities. This is what we are researching at Griffith School of Engineering.

The largest tsunami measurement we have so far is 1.4 metres in Sendai however the biggest tsunami waves often come a few hours after the earthquake. With every increase in magnitude of an earthquake the level of shaking increases about ten times and the amount of energy increases about 32 times. This means that when you compare this event to the earthquake in the same region in 2011, this event involved around 100 times less shaking and around 900-1000 times less energy. But it was still a big earthquake. The difference in terms of the tsunami is that we are talking about waves of up to three metres  instead of 10-20 m.
 
A three metre tsunami can still cause significant damage. Tsunami waves below one metre are likely to only impact cars, people, and less resistant structures but at the three metre mark can damage more significant buildings and structures.
 
This earthquake occurred in the same general area as the 2011 quake but it was smaller so has only affected part of the area. It occurred slightly closer to the coast and was shallower than the quake in 2011 which means that the tsunami waves will reach shore faster.
  
On the NZ earthquake.
 
The Japanese quake and the earthquake in New Zealand are not directly related, one did not cause the other, but are both a result of shifts in the Pacific plate. The Pacific plate is the fastest moving ocean plate so earthquakes occur along the edges of the plate regularly. The earthquake activity we have seen over the last week is not unusual.

The earthquake today, 22 November 2016 is magnitude 6.9 and 10km off the coast. A tsunami of 1m, with a possible increase to 3m has been reported. The seawall at Fukushima Daiichi is 5.7m and will be able to contain this level of tsunami.

The Great East Japan earthquake of 11 March 2011 was magnitude 9.0, 130km off the coast and produced a tsunami of 14m at the Daiichi nuclear power plant within one hour of the earthquake. This flooded the plant and caused the loss of reactor cooling.

Fukushima Daiichi plant parameters currently show all reactor cooling systems normal with reactor temperatures in the range 20-25oC. The heat produced in the reactors is now so low that temperatures cannot rise quickly, even in the event of a prolonged loss of supply.

A magnitude 6.9 earthquake at a shallow depth of 11.4 km below the ground surface and 37 km south east of Namie, in Japan occurred on November 22, 2016 at 20:59:49 UTC.

This earthquake was the result of very complex tectonic activities in the east coast of Japan between four major tectonic plates including the North America plate, Eurasia plate, Pacific plate, and Philippine Sea plate.

Looking at the location of the epicentre, it seems the Namie earthquake has been mainly due to the Pacific plate pushing against the North America Plate (creating compressive stresses) causing subduction of the Pacific plate beneath the North America plate with the average sliding rate of 85mm/year.

The Peak ground acceleration is estimated to be around 0.22g with the maximum ground velocity of 20 cm/s. Since this earthquake happened offshore a Tsunami warning was issued. This earthquake is considered a strong to very strong earthquake with light to moderate possible damage to buildings and infrastructure.

Analysing the initial data indicates that possibly one or several fault lines in the offshore of Sendai toward the south, directing to south west have been activated in this earthquake.

A strong earthquake has struck off the coast of Japan in the same general region that was affected by the 2011 earthquake and tsunami. What we do know is that the highest wave so far has been about 90 cm and that the evacuation process has been running efficiently.

In general, with the size of the earthquake experienced, I would not expect any wave to reach the heights of those experienced in 2011, but that does not mean that this event will not be damaging. Tsunamis as small as 90 cm can be extremely damaging and so in a sense, we are “watching this space”. In this modern age of media communications we are now able to watch live TV coverage and gauge the nature and extent of this event. One concern is not necessarily the size of the earthquake itself but whether or not it might generate submarine landslides that can themselves generate large tsunamis.

Today's event is much smaller than the 2011 catastrophic event. The earthquake maybe an aftershock of the 2011 event. It has affected the same region as the 2011 event

A regional tsunami has been generated - smaller than 2011 but still potentially dangerous.  People who live in the region have been advised to evacuate with authorities taking no chances after the 2011 disaster.

Residents in the region are still struggling to recover from the 2011 event resulting in compound socio-psychological impacts on survivors. Aftershocks will continue in the region for days to weeks to come.

This earthquake was a normal faulting earthquake that occurred at a shallow depth within the plate that overlies the Tohoku subduction zone, which generated the 2011 Mw 9.0 event. It indicates east-west extension within the overriding plate, presumably due to the relaxation of horizontal stress that built up before the 2001 event.  It occurred about 30 km offshore of Fukushima and generated a 60 cm tsunami.  It is very unlikely that this earthquake will have a large impact on Japan.

The recent earthquake off the coast of Japan, near Fukushima, should remind the world that the real harm from such events is from structural, economic and social damage and apprehension, whereas most people outside the immediate area will remember the great earthquake of 2011 for its cause of a nuclear power plant disaster at Fukushima Daiichi – a disaster that did not lead to any discernible injuries due to radiation exposure. The harm caused by the nuclear plant accident was almost entirely in two forms: deaths, injuries and social disruption due to evacuation and other emergency actions that were largely unnecessary; and psychological damage due misinformation and fear of radiation.