by Xinhua writers Tan Huiting and Tian Rui
MEXICO CITY/CARACAS, Aug. 13 (Xinhua) -- A series of powerful earthquakes in Venezuela and Colombia, along with recent seismic events in Peru and Chile, has raised concern over whether South America is entering a period of unusually intense seismic activity.
Experts, however, said there is no evidence of an abnormal increase in earthquakes across the region, and the perception that earthquakes are becoming more frequent may partly reflect faster access to seismic information and heightened public attention after recent devastating quakes caused heavy casualties.
DIFFERENT TECTONIC SETTINGS
A magnitude-7.4 earthquake struck Colombia on Monday, with its epicenter about 20 km from San Jose del Palmar in the western department of Choco and at a depth of 96 km, according to the Colombian Geological Service.
The death toll in Colombia has risen to 281, with 3,971 people injured, 379 missing and more than 100,000 affected, the country's National Unit for Disaster Risk Management said Thursday.
Less than two months earlier, neighboring Venezuela was hit by two powerful earthquakes measuring magnitude 7.2 and 7.5 on June 24. The two shallow quakes, both at a depth of about 10 km, occurred less than a minute apart. Venezuelan authorities have put the death toll at more than 6,300.
Despite their geographical proximity, the earthquakes in Venezuela and Colombia occurred in different tectonic settings.
Feliciano De Santis, president of the Geological Society of Venezuela, told Xinhua that both countries lie on the South American Plate, but the tectonic processes responsible for their earthquakes differ.
In Venezuela, seismic activity is largely associated with the boundary between the Caribbean and South American plates, where horizontal movement produces predominantly strike-slip faulting. Colombia, by contrast, is strongly affected by the subduction of the Nazca Plate beneath the South American Plate.
Those differences help explain the characteristics of the recent earthquakes.
In Venezuela, De Santis said, earthquakes are often shallow, allowing seismic energy to produce particularly intense shaking near the epicenter and fault zone.
The Colombian quake, however, occurred much deeper. Although seismic energy weakens as it travels toward the surface, deeper earthquakes can be felt across a much wider area and produce varying degrees of damage over a broader region.
Andres Folguera, a geologist with Argentina's National Scientific and Technical Research Council, also said the two earthquakes involved different geological processes, with shallow faulting involved in Venezuela and deeper plate deformation behind the Colombian event.
NO EVIDENCE OF ABNORMAL SEISMIC CYCLE
Wang Tun, deputy director of the Key Laboratory of Mountain Hazards and Engineering Safety under the Chinese Academy of Sciences and head of the Institute of Care-Life in Chengdu, said the two epicenters were about 1,200 km apart and that there was no direct stress-triggering relationship between the events.
"They should be regarded as independent earthquakes," he said.
The recent events, Wang added, do not indicate that the South American Plate has entered a period of heightened activity.
De Santis reached a similar conclusion, saying current data provide no sufficient basis for describing seismic activity in South America as abnormal.
According to the Venezuelan geologist, global earthquake catalogs show that strong earthquakes are not rare on a worldwide scale, with roughly 15 to 20 earthquakes of magnitude 7 to 8 occurring in a typical year.
A more systematic assessment of whether 2026 has been unusual would require comparing the full year's global seismic record with data from previous years, he said.
Wang said the growing perception among the public that earthquakes are occurring more frequently is partly related to improvements in seismic monitoring and information services.
People today receive data on earthquake magnitude, location and aftershocks almost immediately, while the severe casualties caused by the recent Venezuela and Colombia earthquakes have further increased public sensitivity to seismic events.
The successive strong earthquakes do not mean that other South American countries also face a higher probability of a major quake this year, Wang said.
Nor would the seismic activity spread along the Pacific "Ring of Fire" toward Asia as a chain reaction, he added, noting that the distance over which stress changes from a magnitude-7.5 earthquake could significantly trigger another event is far smaller than the distance across the Pacific.
Scientists also caution against trying to predict which country might be struck next.
"These things cannot be predicted," De Santis said, stressing that disaster prevention is far more important than attempts to forecast the precise time and location of future earthquakes.
PREVENTION MATTERS MORE THAN PREDICTION
Whether a powerful earthquake develops into a major disaster depends on far more than magnitude alone.
Earthquake depth, local geology, the way seismic waves travel, population density and, crucially, the quality of buildings can all determine the scale of casualties and destruction.
These factors explain why earthquakes of similar magnitudes can produce sharply different outcomes between countries, cities or even neighborhoods within the same city, De Santis said.
For countries along South America's active plate boundaries, experts said, earthquakes themselves cannot be prevented. However, the scale of the disasters they cause can be substantially reduced through safer buildings, effective warning systems and stronger public preparedness.
Wang said current technology still cannot reliably predict when and where the next major earthquake will strike.
"Prevention is more effective than prediction," he said.
Strengthening buildings, expanding the use of seismic isolation and energy-dissipation technologies, improving construction codes and ensuring that those standards are strictly enforced can significantly cut casualties and economic losses, Wang said.
Earthquake early-warning systems and stronger public preparedness are also essential, he added.
De Santis pointed to Chile, one of the world's most earthquake-prone countries, as an example of how strict construction standards can reduce losses from powerful earthquakes.
He said governments in seismic zones should continuously update building codes, strengthen oversight throughout the design, construction, inspection and maintenance process, and assess and reinforce vulnerable existing structures.
Public education is equally important, De Santis said. People should know evacuation routes in their homes, schools and workplaces and understand how to respond calmly and correctly when strong shaking begins, he added. ■
