A powerful earthquake in Colombia has renewed attention on why some earthquakes cause far more deaths and destruction than others. The disaster, which killed at least 250 people, came only weeks after devastating earthquakes in neighbouring Venezuela that claimed more than 6,000 lives.
Moving tectonic plates
Colombia and Venezuela lie near the boundaries of several moving tectonic plates. The constant movement of these plates causes energy to build up beneath the Earth’s surface. When that energy is suddenly released, it produces an earthquake.
According to Colombian geologist German Prieto, the recent Colombian earthquake occurred when the Nazca Plate moved beneath the South American Plate. The U.S. Geological Survey estimated the quake at magnitude 7.4 and about 100 kilometres deep.
Although the earthquake was felt as far away as Panama, its depth allowed some of its energy to dissipate, reducing the potential for even greater destruction.
Magnitude and ground movement
Earthquake magnitude is measured on a logarithmic scale. A magnitude 7 earthquake releases more than 30 times the energy of a magnitude 6 earthquake.
The way the ground moves also matters. The recent earthquakes in Colombia and Venezuela were largely strike-slip earthquakes, involving horizontal movement along faults. This type of movement can produce violent shaking that poses a serious threat to buildings.
Aftershocks can create additional danger, particularly for people returning to structures already weakened by the initial earthquake. Colombia recorded more than 100 aftershocks by Tuesday afternoon.
Buildings and terrain
The quality of buildings and infrastructure can determine whether an earthquake becomes a major disaster.
Countries such as Japan and Chile have strict earthquake-resistant building regulations. Their structures are often designed to be strong but flexible enough to move during intense shaking without collapsing.
By contrast, poorly constructed buildings and informal housing can result in heavy casualties, particularly in densely populated areas.
Colombia began developing earthquake-resistant construction standards in the 1970s and introduced its first building code in 1984. Its current building regulations were established in 2010.
Soft ground can also make earthquakes more destructive. Mexico City, for example, was built on a former lake bed, causing the soil to amplify earthquake vibrations. Similar effects were reported in Venezuela’s coastal La Guaira region and parts of western Colombia.
Preparing for future earthquakes
Scientists say it is impossible to predict or prevent earthquakes, but their impact can be reduced through proper preparation.
Experts recommend stronger building regulations, improved construction standards and wider networks of seismic monitoring stations. Sharing earthquake data between countries is also important because many major faults lie close to national and continental borders.
Scientists warn that the historical earthquake record does not include every possible type of ground movement, meaning communities can still be surprised by the way future earthquakes behave.
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