What makes earthquakes so deadly?

As Colombia reels from one of the strongest earthquakes in its recorded history that killed at least 250, just weeks after more than 6,000 deaths in twin quakes in neighbouring Venezuela, many turned to scientists to learn why this series of tremors was so deadly. Moving plates Colombia and Venezuela sit on the boundaries of several moving tectonic plates, whose slow, constant friction creates a build-up of energy that is periodically released, causing an earthquake. German Prieto, a geologist at the National University of Colombia (UNAL), told Reuters that Colombia’s quake involved the Nazca plate sliding beneath the South American plate far beneath under the earth’s crust, which is just about 40 kilometres deep in the Andean region. The US Geological Survey estimated the magnitude of Monday’s quake at 7.4, striking at a depth of 100 km, versus the 7.2 and 7.5 magnitudes of Venezuela’s late June quakes, at a shallower depth of less than 20 km. A woman walks past the rubble of a collapsed building after an earthquake in Pereira, Colombia on August 11, 2026. —AFP/File The depth of the epicenter in Colombia’s quake sent tremors as far as Panama, but gave energy more room to dissipate, averting a far worse disaster. “Colombia is a seismic country and we have to be prepared for these natural disasters,” Prieto said. “You can’t predict or prevent them, but their effects can be mitigated.” Motion and magnitude An earthquake’s magnitude is measured by a logarithmic scale that gets bigger with every unit, so that a quake of magnitude 7 is more than 30 times stronger than one of magnitude 6. Colombia’s strongest earthquake, one of magnitude 8.8 that struck some 50 km off the northern Ecuadorean coast in 1906, unleashing a powerful tsunami that killed hundreds, released 126 times more energy than Colombia’s latest quake. Another factor is motion. The events in Colombia and Venezuela were strike-slip earthquakes, set off by the horizontal movements of Earth’s cr