Why South America's Recent Quakes Have Been So Lethal
A look at the geological and human factors that made the recent earthquakes in Colombia and Venezuela so destructive.
The recent earthquakes that have devastated parts of Colombia and Venezuela have raised urgent questions about why these tremors proved so lethal. Colombia is still reeling from a magnitude 7.4 quake that killed at least 250 people, just weeks after twin quakes in neighboring Venezuela claimed more than 6,000 lives.
Geologists point to the region's position atop several moving tectonic plates. In Colombia's case, the Nazca plate is sliding beneath the South American plate. The U.S. Geological Survey placed Monday's quake at a depth of 100 kilometers, which sent tremors as far as Panama but allowed energy to dissipate before causing even greater destruction.
Venezuela's June quakes, with magnitudes of 7.2 and 7.5, struck at a much shallower depth of less than 20 kilometers. Shallower quakes concentrate their energy closer to the surface, making them far more dangerous for buildings and people.
Magnitude alone doesn't tell the full story. The logarithmic scale means a magnitude 7 quake is over 30 times stronger than a magnitude 6. Colombia's deadliest recorded earthquake, an 8.8-magnitude event off the Ecuadorean coast in 1906, released 126 times more energy than this week's tremor.
The type of motion also matters. Both the Colombian and Venezuelan quakes were strike-slip events, caused by horizontal movement of the Earth's crust. This produces a shaking pattern that is particularly damaging to structures. Aftershocks add to the danger, with Colombia registering more than 100 by Tuesday afternoon.
Infrastructure and terrain play a decisive role in determining casualties. Chile and Japan enforce strict building codes that allow structures to flex without collapsing. In contrast, informal housing and weak engineering can turn a moderate quake into a catastrophe, as seen in Haiti's 2010 earthquake, which killed over 300,000 people.
Colombia adopted its first earthquake-resistant building code in 1984 and updated it in 2010, but experts say compliance and local conditions remain critical. Soft soils, like those in Mexico City or Venezuela's La Guaira coast, amplify shaking and worsen damage.
Seismologists stress that while earthquakes cannot be predicted or prevented, their impact can be reduced through preparation, robust construction, and international data sharing. As one expert noted, the geological record is long but incomplete, and surprises are inevitable. The key is building resilience before the next tremor strikes.