Earthquakes generally occur when they’re the last thing you’re thinking about. You can’t live your life worrying every day if today will be when it happens. The knack instead is to know what to do when a bad one hits and be prepared to cope if necessary for several days without official assistance. Individuals need to take personal responsibility for ensuring they have food, water, torches, batteries, a radio and cash on hand in an emergency kit. PHOTO: GETTY IMAGES Thursday evening’s strong earthquake in remote Fiordland shook up residents of the South, especially locals in Te Anau, Milford Sound and Queenstown. Yesterday morning, assessments were under way of damage to some homes and of whether the quake had compromised bridges and roads. Fortunately, there were no injuries. The time of day, 9.14pm, helped, most people being inside and tucked up or close to it for the night. However, the mental trauma of going through a significant earthquake should not be minimised. Fiordland is the country’s most seismically active region. It experiences relatively frequent large earthquakes, some of them very powerful indeed, and there are always smaller tremors occurring which, due to its hard-to-access terrain, go undetected because of a much sparser network of seismometers there. This latest quake was triggered about 50km below the surface in the mountains between George Sound and the Northwest Arm of the Middle Fiord of Lake Te Anau. There are different scales for recording magnitude, but GeoNet registered the quake as 6.3 on the local magnitude scale while the United States Geological Survey measured it as having a moment magnitude of 5.9. That makes this the largest Fiordland quake in 17 years, almost to the day. At 9.22pm on July 15, 2009, a magnitude-7.8 earthquake struck near Dusky Sound, further south than Thursday’s. It was the strongest quake since the February 3, 1931, Hawke’s Bay event and caused a small tsunami and set off hundreds of landslips. On August 21, 2003, at 12.12am, there was a 7.2-magnitude earthquake just offshore of Secretary Island, felt as far away as Sydney, and 10 years earlier, on August 10 at 12.51pm, a magnitude-7.0 was centred in almost the same place. Looming not far away from the steep peaks and fiords is the Alpine Fault, which runs offshore at the mouth of Milford Sound and marks the boundary between the Australian and Pacific plates. Scientists give this a 75% chance of rupturing in the next 50 years and generating a magnitude-8 or thereabouts earthquake. There are major concerns about the possible death toll from a tsunami in Milford Sound following such a quake or as a result of large-scale landslips. Questions were asked yesterday about the robustness of the Civil Defence website on Thursday evening and why the National Emergency Management Authority issued a tsunami warning for the coast from Milford Sound to Puysegur Point. Officials have apologised for the site going down at a key time, apparently due to a firewall-related problem. Director of civil defence emergency management John Price told RNZ ‘‘you cannot always rely on technology’’ and that was why there were also emergency mobile phone alerts, social media posts and radio announcements during these events. A phone alert for a possible tsunami was issued to about 40 people living near Milford Sound within 10 minutes of the quake. That was after receiving advice from Earth Sciences New Zealand, he said. A local-source tsunami is likely to have hit the shore well before 10 minutes is up. But the question is, was a tsunami warning actually warranted? After all, the earthquake was generated deep under the Fiordland mountains, almost 30km in a straight line from the open sea. ESNZ says it made a rapid decision of the tsunami risk, thinking the seafloor could have been displaced or landslips triggered, based on the quake’s size and location. Once it was better assessed about 20 minutes later, their advice changed. Evacuating to higher ground was great practice for those who live by the sea. But it seems the warning was made purely out of an abundance of caution. Damned if you do and damned if you don’t. But this is another timely reminder for us — that blanket warnings can cause warning fatigue, and the repercussions of that in a real emergency don’t bear thinking about.
