Geology And Geophysics

Laquila Earthquake in Italy 2009

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"Laquila Earthquake in Italy 2009"
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The city of L'Aquilia (population approximately 68,500) and several nearby medieval towns and villages in the Abruzzo region of central Italy were hit by an earthquake on the morning of Monday 6 April 2009. The earthquake injured over one thousand people, left an estimated 40-50,000 homeless, and killed 289 people. There were a number of reasons why so many people died in this earthquake, and there has been much hysterical nonsense written about what caused the death toll and what could have been done to prevent so many deaths.

1. The Type and Power of the Earthquake

The first factor to consider in the death toll of the earthquake that struck L'Aquila and surrounding towns and villages is its type and power. The earthquake measured 6.3 on the Richter scale, which was strong enough to be felt through most of central Italy, and to cause damage as far away as Rome. The earthquake was a shallow type with a focus about 10 km (6 miles) underground, and very close to L'Aquila. Shallow focus earthquakes cause much more violent shaking, and hence damage to buildings, than those occurring deeper underground.

If the April 6 earthquake had been an isolated quake out of the blue it is doubtful that a 6.3 magnitude quake would have caused as much damage as it did, but it came after several months of tremors and minor quakes, including a 4.8 magnitude quake that struck the region the day before. The day the earthquake struck, many of the buildings were already structurally weakened or damaged.

2. The Time of Location of the Quake

The next factor to be considered is the time and location of the quake. In this case the epicentre of the earthquake was very close to the heavily populated area of the city of L'Aquila. In any earthquake, the more densely populated the area, the higher the death toll is likely to be. In this earthquake a large proportion of the population were exposed to the dangers of the ground shaking.

The quake hit at 3.32 am local time, which meant that most people were home in bed asleep when the earthquake struck. Many people died in their beds. If the earthquake had struck later in the day when people were out and about, it is quite possible the death toll would have been lower.

3. The Type of Earthquake Zone

The earthquake zones in central Italy are unlike the well-known earthquake zone in California, located around the San Andreas fault. In California there are two tectonic plates moving against each other, and the slippages as tension is released cause the ground to shake. In Italy the earthquake zone is much more complex with the tectonic plates of Africa and Europe being fractured into many micro-plates that move around and create different kinds of faults as they move against each other. There are two major fault systems running north-south and east-west. The L'Aquila earthquake was caused by faulting along the east=west extensional tectonic plates.

Some have suggested that the death toll was high because warnings were ignored and the towns should have been evacuated. The fact is however, that it is not possible to predict the time and location of future earthquakes with any accuracy, and incorrect predictions can cause panic that could be disastrous. It is also not sensible to try to compare the earthquakes in California with those of Italy because their features are so different, and in Italy they are so variable. There had been several minor earthquakes and tremors in the region, especially in the weeks preceding the earthquake, but you cannot evacuate an entire population indefinitely on the off-chance there may be a major earthquake, especially when no major earthquake had hit the region for over 300 years.

4. The Strength and Type of Buildings

Another factor to be considered is the type and strength of buildings in the region. Over 40% of the buildings in L'Aquila were damaged by the quake, with about half of those being uninhabitable. More than 4000 buildings collapsed and most of those had not been specifically designed to withstand earthquakes. As a result there have been accusations that the high death toll was due to poor building codes in the new buildings that were affected.

The problem with this idea is that many of the buildings damaged were medieval and had stood for several hundred years, through all the earthquakes (and wars) of the period. There have been many minor earthquakes in the region in the past, but none of the magnitude of the 2009 earthquake since 1703. Some of the medieval buildings had been damaged in the 1703 quake, such as the cathedral, but many of the buildings were built in the 14th, 15th and 16th centuries, and had withstood everything that nature could throw at them.

Among the medieval buildings damaged in the quake of April 6, 2009 were the Roman Baths in Caracalla (built in AD216), the 16th-century castle in L'Aquila, housing the National Museum of Abruzzo, the bridge, the Porta Napoli (built in 1548), along with numerous other historical buildings. Are the critics who suggest that all buildings that do not meet modern building codes should be knocked down? Such a hysterical response would obviously be absurd. Retrofitting existing medieval buildings is also extremely difficult and expensive.

It is true that many of the modern buildings were not specifically designed to withstand earthquakes, but in a region that has had no major earthquake for over 300 years, it is understandable that this was not taken into account in the design process. It obviously should be taken into account in the future. There are ways to design buildings that are earthquake-resistant, and in areas of extreme seismic activity such as California, it makes sense to insist on adherence to such strict building codes. Perhaps it also makes sense to consider this in Italy too.

The April 6 earthquake followed some four months of smaller tremors, including a magnitude 4.0 earthquake on March 30 and a magnitude 4.8 quake the day before. The relatively high death toll was undoubtedly due to a combination of factors, especially the location of the epicentre being so close to populated areas, and the fact that a series of tremors and small quakes over the previous month or so had already caused structural weakening of many of the buildings. It is a terrible tragedy, but natural disasters are a fact of life, and it is simply not possible to prevent all deaths from earthquakes.

More about this author: Anne StClair

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