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Earthquakes perhaps not our main concern

With each new year comes consternation about new disasters. Because of Christchurch three years ago the most obvious worry in NZ is possible earthquake risk. But since then the possibility of repeat events may have been overblown by media.

Earthquake magnitudes have internationally been assigned grade words. "Great" earthquakes of 8M or higher occur at least once a year on average somewhere around the globe. We can take some comfort in the fact that the last time an above-8M occurred on NZ soil was 1855.

A "major" shake of 7-7.9M occurs globally once every three weeks, but our country has had only four of these since 2010. "Strong" shakes of 6-6.9M happen every 2.7 days somewhere, but NZ has had only 13 in the past 2 years. About 4 "moderate" earthquakes of 5-5.9M occur every day but the rate for NZ is an average of one every 4 days.

"Light" earthquakes of 4-4.9M are large enough to frighten and the norm is for 35 on any given day. In NZ the rate is one every second day. "Minor" shakes of 3-3.9M can be experienced as far-off rumbles and are large enough to be noted - these on average happen globally at the rate of one every 4 minutes. NZ gets about one every 24 hours.

These figures are continually changing upwards as more seismic stations are established detecting both deeper and more remote events, but there is no reason to believe that total numbers of earthquakes in the world are getting averagely higher than at any time in the past, and that includes for NZ.

Of course loss of life always concerns us. NZ gets about 15000 recorded earthquake events per year. But the big ones have only been a handful. They were the Wellington earthquake of 1855, the 1886 Lake Tarawera eruption, the 1929 Murchison earthquake, the 1931 Napier earthquake and the February 2011 tragedy, with relatively few earthquake deaths. Around 600 fatalities in NZ overall have spanned 200 years, which averages three per year. Compare that to the NZ road toll which is about 500-600 per year.

Further, the tragic earthquake deaths in Christchurch during 2010-11 were mostly in one building on one tragic day and were described at our Royal inquiry as an accident waiting to happen because of dodgy renovations of a modern building involving departures from the building code. The Christchurch City Council wore some blame for the high death count rather than the quake. During the actual earthquake period, damage covered the whole region but did not cause equally widespread loss of life.

In the smaller time frame of repeating solar/lunar cycles, clustering can be loosely predicted by what has gone before. Examination of cycles suggests earthquakes could be relatively quiet over the next year at least in NZ , and that the next large (above 7M) earthquake risk for us may be around 2015-16.

Yet some may be considering leaving certain regions. Earthquake activity has indeed increased over the past four years but so in the North Island than the South Island, which has not been well publicised. Earthquake size and frequency has not been that far from normal when averaged over a longer timeframe.

A major problem in NZ seems to be quick recovery. Re-housing newly homeless after a catastrophe requires adequacy of compensation. We have a good civil defence organisation which sits idle most of the time due to lack of use, which is why when required it has been a tad slow getting going.

Administrative and compensatory failure is simply because there have been few fatalities in NZ as a result of catastrophic events. If our history had been more disaster-studded then public outrage would have sorted better after-strategies many years before now, and of this Japan is a good example. Recovery-slowness is part of our political landscape and may happen again post- disaster regardless of where one moves to.

Considering relocating because of earthquake risks is completely understandable given what trauma some families went through and may still be experiencing. Moving from the top or bottom of a cliff would be wise at any time due to the constant threat of ground movement from erosion and slips. But larger destructive earthquakes seldom hit again at the exact same spot, or no one would choose to live in Napier, Edgecumbe, Lake Tarawera, Taupo or Wellington.

The media have a lot to answer for because alarmism sells. Because of the relatively recent proliferation of free online information, print media is facing a decline and is scrambling to retain profits. Stories are getting more fantasy-laden and reportage more emotive. Now, more than ever, readers need to exercise their own instincts of real dangers of impending storms, floods, snows or droughts. We might have happier families if we could find a way to ignore the daily tabloid onslaught of fictional dangers and baseless threats e.g. of imminent tsunami wipe-outs or Alpine Fault blowouts that are mostly business driven.

Potential catastrophes that have never happened or happened long ago are arguably dismissible after a certain period of time. But a now accepted stance of alarmist science is if that we can imagine it, then it will happen, if not now then one day, and media attention which will morph into study projects because of heightened public interest.
This attitude wastes government spending that could be better deployed servicing current social needs. If there is no proven evidence of high risk, is it really worth getting concerned about? Do we not also have a responsibility to children to shield them from unproven fears? Must children always be on some lookout now for catastrophes? As I recall, it was hard enough just growing up.

Ken Ring of www.predictweather.com is the author of the Weather Almanac for NZ, 2014