As Japan rebuilds, Christchurch still in limbo a year after quake

One year after the natural disasters that devastated Japan and New Zealand, the progress in the two countries could not be more different.

Illustration by Sarah Lazarovic for The National

This is a tale of two earthquakes.

The first hit Christchurch in New Zealand and then, just as all hope faded of any more survivors being rescued from the rubble, a far bigger quake rent the sea floor off the east coast of Japan, unleashing a devastating tsunami.

By any reckoning, the Japanese earthquake was huge. Measuring 9.0 on the Richter scale, one of the factoids that best demonstrates its magnitude is that it shifted the Earth on its axis by between 10cm and 25cm, prompting Nasa scientists to reassess the trajectories of deep-space rockets it planned to launch.

All this increases the impact of before-and-after pictures of the Japanese quake that have been circulating via social media and email as the first anniversary approaches.

Images of wanton destruction in the immediate aftermath of the tsunami stand in stark contrast to the scene from the same viewpoint now. In many cases, there is no hint of the cataclysmic events.

Christchurch's earthquake, by contrast, measured 6.3, and involved less than one per cent of the force of the Japanese quake. But the relative lack of similarly impressive before-and-after photos emerging from New Zealand hints at a truth that the respective quake magnitudes don't reveal.

It's part of the reason why Christchurch's residents are now familiar with the scientific debate that saw the old Richter scale fall out of academic favour compared to what's known as the modified Mercalli intensity scale. The old scale measures earthquake magnitude but the Mercalli scale measures its effects.

While the Japanese quake had been big, its epicentre was 70km offshore and at a depth of 34km. Christchurch's much smaller February 22 earthquake was less than 10km from the city centre and at a depth of less than 5km. For earthquakes, shallow is bad.

The Mercalli intensity scale divides quakes into 12 categories, ranging from one (barely perceptible) to 12 (cataclysmic). Unsurprisingly, the Japanese quake was given a Mercali score of nine, a rating associated with considerable destruction and in the top 10 since accurate records began a little over a century ago. More surprisingly, the Christchurch quake was also given a Mercalli score of nine.

Or at least that's not a surprise to anyone who was in Christchurch on February 22, where the ground acceleration was measured at 2.2 times the force of gravity, among the highest ever recorded.

One final statistic helps explain the lack of restoration photos from Christchurch. After the devastating March 11 earthquake, Japan's tectonics settled down again and there have been a little over 1,800 aftershocks.

If the citizens of Christchurch now take a kind of dark pride in being dab hands at guessing the magnitude of the tremors, it's because since the quakes began 18 months ago, they've lived through well over 10,000 of them, ranging from the gentle to, as they saw on February 22, the devastating.

Amateur intensity assessment is one of the few upsides. Local reconstruction involves the global reinsurance market and many such corporations won't underwrite Christchurch's reconstruction until the quakes diminish, often defined as three months since an earthquake of 4.0 on the Richter scale is recorded.

Within three days of the anniversary commemorations in Christchurch nine days ago, the city experienced two that were both greater than 4.0.

So while Japan rebuilds, Christchurch's residents are caught in an unsettling state of limbo.

Most of the city centre remains cordoned off and the demolition of its biggest buildings is yet to occur. Thousands of homeowners are yet to hear if their land will be zoned green (allowing repair and rebuilding) or red (never to be built on again).

The human toll of that is evident: stress-indicating behaviours - problem gambling, drinking and domestic violence - are way up, as is the prescription of anti-depressants and the number of people leaving the city for good.

So as the first anniversary of the Japanese quake comes up on March 11, spare a thought for those in Christchurch who had a supposedly gentler and less destructive earthquake.