Mexico+City+Earthquake

[[image:mexico_city.jpg width="262" height="179" align="right"]]
__** Where it happened **__
 * Mexico is located in Central America between North and South America.
 * Capital – Mexico City.
 * East of the Pacific Ocean and west of the Caribbean Sea.
 * Population – 111,211,789
 * GDP per capita - $14,534
 * HDI – 0.854
 * Former Spanish colony
 * __What happened__ (McLeish 2007) **
 * 19th September 1985
 * Occurred 65 km off the Pacific (west) coast of Mexico.
 * Measuring 8.1 on the Richter scale.
 * Quake was felt as far away as Houston, Texas (1,200 km north)
 * Quake struck at 7:17am and lasted for approx 3 minutes.
 * On Pacific coast – part of a mountain broke away falling onto farm labourers.
 * Approx 10,000 deaths reported but as thousands of bodies were never found, actual figure 60,000 – 100,000.
 * 50,000 people injured.
 * 250,000 – 300,000 people made homeless.
 * Total cost of damage – US$12.5 billion.
 * Much of the infrastructure destroyed and collapsed and some were on fire, aided by ruptured gas pipes.
 * Communications damaged and underground railway failed and many were trapped win the tunnels.
 * US Mexican Embassy issued a Tsunami warning along western South and North American coasts – some coastal areas experienced a mini Tsunami but caused less damage then originally feared.
 * __Why it happened__ **
 * Subduction zone – destructive plate margin
 * Oceanic Cocos plate subducted beneath continental North American plate.
 * Mexico City was damaged mostly even though it wasn’t located on the epicentre and it sits on a broad river basin formed about 30 million years ago.
 * Lava thrown out of nearby volcanoes blocked entrance to basin and created Lake Texcoco.
 * As the capital expanded, the lake was drained leaving the densely populated city located on soft clay.
 * The layers of the clay made the seismic waves 50 times stronger, phenomenon known as Resonance.
 * The vibrations caused sub-soils to behave like liquid due to liquefaction and this caused many buildings to sink into the ground.
 * __Future plans__ **
 * Mexican government funded a sophisticated early warning system.
 * When seismic activity occurs, sirens automatically sound giving the people a minutes warning before the quake.