A magnitude 7.4 earthquake that struck western Colombia has resulted in over 100 fatalities, raising questions about the significant damage caused despite the quake originating from a depth exceeding 100 kilometers.
According to reports from the Associated Press and Reuters, the earthquake occurred at 7:34 a.m. local time on August 10 near San José del Palmar in Chocó province. The U.S. Geological Survey (USGS) reported the epicenter was at a depth of 107 kilometers, marking it as the strongest earthquake recorded in Colombia in the 21st century.
At least 111 people have died, and 87 others have been injured. The Colombian government reported that approximately 1,600 buildings were damaged, with at least 61 completely collapsed. Areas such as Pereira, Cali, Chocó, and Manizales experienced significant destruction.
Typically, earthquakes that occur at greater depths result in weaker surface shaking. The USGS explains that for earthquakes of the same magnitude, the shaking diminishes with distance from the epicenter, indicating that a quake at a depth of 500 kilometers would produce much less surface shaking than one at 20 kilometers.
The depth of this earthquake, between 103 and 107 kilometers, is classified as a 'mid-depth earthquake' in seismology. The USGS categorizes earthquakes based on depth: shallow (0-70 km), mid-depth (70-300 km), and deep (300-700 km). Thus, this earthquake was considerably deeper than shallow earthquakes.
Despite its depth, the earthquake's magnitude of 7.4 is cited as a primary reason for the extensive shaking experienced. Earthquake magnitude is measured on a logarithmic scale, and according to the USGS, an increase of 1 in magnitude results in a tenfold increase in the amplitude of seismic waves and approximately 32 times more energy released. This indicates that even with reduced surface shaking due to depth, the energy released by the earthquake was substantial.
Susan Vanderleest, a seismologist at Northwestern University, noted that while the earthquake occurred at a significant depth, the large magnitude resulted in strong shaking. She suggested that the quake's size, its inland location, and the strike-slip fault movement may have contributed to the damage in densely populated valley areas.
The impact of an earthquake is not determined solely by depth or magnitude. The USGS states that the intensity of shaking felt in a specific area can vary based on several factors, including the distance from the fault rupture, the direction of the rupture, and the geological conditions of the surface. This means that even the same earthquake can result in different levels of shaking and damage in different locations.
Meanwhile, the Colombian Geological Survey reported that 21 aftershocks were recorded by late on August 10, with the possibility of additional aftershocks occurring.
* This article has been translated by AI.
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