Ascension : Met Office Ascension Island Base - The Met Office Weather Report
Submitted by The Islander (Met Office) 09.09.2010 (Article Archived on 23.09.2010)

UK - A dry and pleasant start to the week with plenty of sunshine, but this turned to outbreaks of rain, particularly in the west, by the weekend.

Past week’s Weather

A small earthquake and engineering related interlude…

the early hours of Saturday morning large parts of the South Island of New Zealand were woken by the shaking and destruction caused by an earthquake measuring 7.0 on the Richter scale.  The epicentre was approximately 13 miles west of Christchurch and it has been estimated that two thirds of houses in the city have been damaged, many becoming structurally unsafe.  Although there have been reports of damage and power outages from as far a field as Dunedin (223 miles to the south west of Christchurch), there have thankfully only been 2 serious injuries.

The mayor of Christchurch has declared a State of Emergency since the quake due to the large numbers of buildings damaged and people affected.  Which got me thinking…earthquakes are not a new invention…New Zealand itself is thought to experience more than 14,000 earthquakes a year with only 20 or so having a magnitude in excess of 5.0.  And there are other areas of the world which are particularly earthquake prone so why isn’t every building destroyed at even the smallest of quakes?  The answer lies in their design.

For many years engineers have struggled to combat the effects of seismic activity within structures and there are a variety of different solutions to the problem.  Some involve mounting huge concrete blocks within the building which are designed to damp the oscillations that build up by moving in opposition to them.  The Taipei 101 skyscraper uses a steel pendulum weighing 660 tons and is suspended within the building from the 88^th to the 92^nd floor.  Other methods try to isolate the base of the structure from the ground underneath, allowing the two things to move independently.  Apparently the Mausoleum of Cyprus is the oldest structure of this type in the world.  In Peru the Inca civilisation built dry stone walls so that they could move slightly and resettle without collapsing.

Different methods are used in different situations across the world with the aim of designing buildings in earthquake prone zones to withstand ‘the Big One’.  The question is how big will ‘the Big One’ be?!  In New Zealand a network of instruments across the island records data which is then used by engineers to inform building regulations.  This is so that buildings of the future can hopefully withstand whatever is to come.