Once the adrenalin, shock and awe wear off, Cantabrians and all New Zealanders will recognise that Saturday's devastating earthquake was most remarkable for its lack of casualties.

A shallow, fierce earthquake which could cripple around 500 buildings in a built-up urban environment and cause around $2 billion in damage did not directly claim a life with its force.

The word "miracle" is overused and thus devalued, yet Canterbury's fortune in misfortune comes close to warranting the freakish, supernatural meanings that it conveys.

Those affected will not be feeling necessarily fortunate. Beside the crushing physical damage to homes, businesses, offices and cars, which can in itself overwhelm the most stoical, lives and dreams are ruined.

The psychological damage and fear will remain for many, particularly children, long after the diggers and men in high-visibility vests disappear. Urban services we rely on so unthinkingly are shown to be fickle in the face of nature's violence; basics such as power and water, phones, roads and drains taken away in an instant.

The timing of the 4.35am earthquake seems to have been critical in preserving lives. Few people appear to have been moving about on the city pavements which were covered with debris or driving on roads splintered by cracks or slips.

Even in homes which were broken apart by the shake, residents by and large found themselves spared. One man hit by falling masonry remains in Christchurch Hospital's intensive care ward; most others presented with moderate injuries only.

Even far less severe earthquakes and natural disasters have killed, leaving families and communities to grieve and try to farewell loved ones amid the ruins of their homes and towns.

One expert pointed out on Saturday that the Canterbury earthquake was similar in force to that which caused hundreds of thousands of deaths in Haiti, a more densely populated and poorly constructed location.

Christchurch and its neighbouring centres face an unprecedented reconstruction effort in local terms. The reassurance so carefully spelled out by Prime Minister John Key of Earthquake Commission funding and of central government assistance will help to provide hope of resolution. Mr Key's urgent visit to the city of his childhood was a necessary duty performed with clarity and purpose.

Civil defence and emergency service officials also acted and communicated through the weekend to a high standard of professionalism. Authorities can plan for such disasters but the reality, as in Christchurch, is that they must deal with peculiar circumstances.

It must have been difficult for the first 90 minutes or so of darkness to estimate reliably the extent of the catastrophe. Once assessments could be made and reports collated, the civil defence response seemed better than for the near-misses of threatened tsunamis in the past few years.

Beyond Canterbury, New Zealanders have been jolted back into a realisation that their country is known as the Shaky Isles for a reason. Earthquake experts have repeated their predictions of a major shake in Wellington and probably something bigger still along the alpine fault of the South Island.

The message from Civil Defence to be prepared as a household, community or business for the "big one" no longer seems like so much over-caution.

One piece of infrastructure in Auckland was out of action for a short time at the weekend, with widespread although well-managed effects.

Christchurch now faces weeks if not months of being without multiple roading or utility services, even its main university and much of its central business district.

The city and region will need the resources of central government and the goodwill of their fellow Kiwis to make the unbearable bearable. We must offer whatever it takes.