New Zealand earthquake disrupts infrastructure and raises the sea bed

Monday's earthquake that hit New Zealand's South Island was - at 7.8 on the Richter scale - significantly more powerful than the 2010 Christchurch one that resulted in 185 fatalities (6.3). Yet the fact that it occurred just past midnight and had its epicentre in a sparsely population rural area 57 miles north east of Christchurch meant the 23 km deep tremor directly affected relatively few people. Two deaths were reported; one from a building collapse and the other suspected of being due to an underlying health condition. There is a dramatic set of images and report from the Daily Telegraph here.

The major impact is on key infrastructure disruption. Railway tracks were 'flipped' tens of metres away from their route onto an adjacent road; roads buckled, cracked and were severely distorted; river channels were blocked by falling rocks creating temporary dams; and landslides blocked a number of road and rail routes. One of the most shared video clips has been of three isolated cattle standing on an island of ground after the surrounding farmland has subsided and collapsed. (See below for a clip from the Guardian website).

Tsunami warnings were issued to people living along the eastern coast of South Island with calls for residents to move inland to higher ground. In the end, the waves were no more than 2m high and had little impact but there was a lifting of the coastal sea bed that revealed seaweed-encrusted rocks that were previously submerged. Tectonic uplift, such as this, is known as a isostatic change in sea level. It affects regions at a local scale and can occur as a result of significant ice-mass change, uplift, or seismic activity and can be seen in footage from BBC News here.

New Zealand has had to absorb the cost of three severe earthquakes in recent years: in 2010, 2011 and now in 2016. The repair costs of this latest one is estimated to exceed 2bn (NZ) dollars (about £1.1bn). For a country with a population of around 4.3 million, that withdraws a lot of tax revenue from other expenditure demands.