Steve Connor: Island is cut across with fault lines

Share
Related Topics

The Caribbean is riddled with a complex network of tectonic fault lines resulting from the movement of the Caribbean plate which is slipping eastwards at a rate of about 2cm a year, relative to the vast North American plate further to the north.

The boundary of these two tectonic plates lies off the north coast of Haiti but there are several fault-line systems to the south that cut across the country from east to west. It was the sudden "strike-slip" movement of one of these fault lines, the Enriquillo-Plantain Garden fault zone, that led to the disaster.

Scientists calculate that the epicentre of the earthquake, which measured 7 on the Richter scale, was approximately nine miles south-west of Haiti's capital, Port-au-Prince. The point beneath the Earth's surface where the rupture began – its hypocentre – was just six miles away, making it a relatively shallow shock.

"Closeness to the surface is a major factor contributing to the severity of ground shaking caused by an earthquake of any given magnitude," said David Rothery, a planetary scientist at the Open University. "Furthermore, shaking tends to be greatest directly above the source. In this case, the epicentre was only 15km from the centre of Port-au-Prince, which therefore suffered very heavily."

The seismic waves from the initial shock took about 10 minutes to reach the Edinburgh monitoring station of the British Geological Survey (BGS). Scientists there said yesterday that it was the largest earthquake to affect this area of the Caribbean for more than two centuries.

"The situation in Haiti is similar to the San Andreas Fault in California, in that two plates are sliding past one another. The fault in this case is called the Enriquillo-Plantain Garden fault. This fault has been locked for the last 250 years, gradually accumulating stress which has now been released in a single large earthquake," said Roger Musson, a BGS seismologist. "The rupture occurred over a distance of some 17km and the ground probably moved more than a metre. It was a shallow shock and it probably resulted in the rupture of the whole of the Earth's crust above it.

"Most people in Port-au-Prince probably didn't realise they live in an earthquake zone and earthquake safety was not on their list of priorities because the last one there was not within living memory."

Haiti suffered a number of earthquakes in the 18th century: in 1701, 1751 and 1770. The 1751 earthquake, which was probably about 10 times bigger than the current shock, destroyed the recently founded Port-au-Prince and caused severe damage to buildings in neighbouring areas.

According to the US Geological Survey (USGS), the Enriquillo-Plantain Garden fault accommodates a movement of about 7mm a year, nearly half the rate of movement along the boundary of the North American and Caribbean tectonic plates. The USGS has measured more than 30 aftershocks.

"Earthquakes of this size always have aftershocks that can last for many weeks," said Brian Baptie, a seismologist at the BGS. "These always punch above their weight, affecting buildings that have already been damaged and hampering relief efforts."

Landslides are another hazard as they can block roads and cause devastation to the flimsy homes of mountain villages and shanty towns built on hillsides around the capital, said David Kerridge, head of earth hazards at the BGS.

Professor Roger Searle, an earth scientist at Durham University, said that the earthquake released the energy equivalent of half a million tons of TNT but its impact would have been much greater than in developed countries because of poor building standards.

Deadliest earthquakes since 1900

28 July 1976 A 7.5 Richter scale quake struck the city of Tangshan in north-east China, claiming at least 250,000 lives, believed to be the highest earthquake death toll of the 20th century.

26 December 2004 The Boxing Day tsunami was triggered by an earthquake measuring 9.2 on the Richter scale. Some 230,000 people died, across 14 countries.

16 December 1920 A 7.8 quake killed up to 200,000 people in central China's Haiyuan County.

12 May 2008 Up to 87,000 people were killed in China's south-western Sichuan province when a quake measuring 7.8 struck 50 miles from the provincial capital Chengdu, less than a week after Cyclone Nargis struck Burma, killing 146,000.

8 October 2005 An earthquake measuring 7.6 struck northern Pakistan and the disputed Kashmir region, killing 73,000.

31 May 1970 A quake in the Peruvian Andes triggered a landslide, burying the town of Yungay and killing 66,000 people.

21 June 1990 Around 40,000 people died in a tremor in Gilan province, north Iran.

26 December 2003 More than 26,000 lives were claimed when an earthquake destroyed the historic city of Bam in southern Iran.

7 December 1988 An earthquake, 6.9 on the scale, struck north-west Armenia, killing 25,000.

17 August 1999 A magnitude 7.4 earthquake hit Izmit and Istanbul in Turkey; 17,000 died.

React Now

Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Tradewind Recruitment: English Teacher

Negotiable: Tradewind Recruitment: My client is an excellent, large partially ...

Tradewind Recruitment: Science Teacher

£90 - £140 per day: Tradewind Recruitment: I am currently working in partnersh...

Tradewind Recruitment: Year 3 Primary Teacher

£100 - £150 per day: Tradewind Recruitment: Year 3 Teacher Birmingham Jan 2015...

Ashdown Group: Lead Web Developer (ASP.NET, C#) - City of London

£45000 - £50000 per annum + Excellent benefits: Ashdown Group: Lead Web Develo...

Day In a Page

Read Next
 

i Editor's Letter: Science versus religion in the three-parent baby debate

Oliver Duff Oliver Duff
Kylie has helped to boost viewing figures for the talent show  

When an Aussie calls you a ‘bastard’, you know you’ve arrived

Howard Jacobson
Isis hostage crisis: The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power

Isis hostage crisis

The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power, says Robert Fisk
Missing salvage expert who found $50m of sunken treasure before disappearing, tracked down at last

The runaway buccaneers and the ship full of gold

Salvage expert Tommy Thompson found sunken treasure worth millions. Then he vanished... until now
Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

Maverick artist Grayson Perry backs our campaign
Assisted Dying Bill: I want to be able to decide about my own death - I want to have control of my life

Assisted Dying Bill: 'I want control of my life'

This week the Assisted Dying Bill is debated in the Lords. Virginia Ironside, who has already made plans for her own self-deliverance, argues that it's time we allowed people a humane, compassionate death
Move over, kale - cabbage is the new rising star

Cabbage is king again

Sophie Morris banishes thoughts of soggy school dinners and turns over a new leaf
11 best winter skin treats

Give your moisturiser a helping hand: 11 best winter skin treats

Get an extra boost of nourishment from one of these hard-working products
Paul Scholes column: The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him

Paul Scholes column

The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him
Frank Warren column: No cigar, but pots of money: here come the Cubans

Frank Warren's Ringside

No cigar, but pots of money: here come the Cubans
Isis hostage crisis: Militant group stands strong as its numerous enemies fail to find a common plan to defeat it

Isis stands strong as its numerous enemies fail to find a common plan to defeat it

The jihadis are being squeezed militarily and economically, but there is no sign of an implosion, says Patrick Cockburn
Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action

Virtual reality: Seeing is believing

Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action
Homeless Veterans appeal: MP says Coalition ‘not doing enough’

Homeless Veterans appeal

MP says Coalition ‘not doing enough’ to help
Larry David, Steve Coogan and other comedians share stories of depression in new documentary

Comedians share stories of depression

The director of the new documentary, Kevin Pollak, tells Jessica Barrett how he got them to talk
Has The Archers lost the plot with it's spicy storylines?

Has The Archers lost the plot?

A growing number of listeners are voicing their discontent over the rural soap's spicy storylines; so loudly that even the BBC's director-general seems worried, says Simon Kelner
English Heritage adds 14 post-war office buildings to its protected lists

14 office buildings added to protected lists

Christopher Beanland explores the underrated appeal of these palaces of pen-pushing
Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

Scientists unearthed the cranial fragments from Manot Cave in West Galilee