The Devastating Impact of the Caraballeda Earthquake

The earthquake that hit Caraballeda, Venezuela on June 24 caused severe destruction across coastal areas. The quake disrupted life for residents in cities like Caracas, La Guaira, and Catia La Mar. The combination of two sequential earthquakes, geological conditions, and shallow depth contributed to the magnitude of the disaster.

The Twin Earthquake Phenomenon

The main reason for the unprecedented damage was the occurrence of two earthquakes within 39 seconds, known as a ‘doublet.’ Initially, a quake of 7.2 magnitude occurred, followed by a more intense 7.5 magnitude tremor. This pattern forced structures to endure prolonged, chaotic shaking, testing their limits far beyond normal conditions.

David Oglesby, a geophysics professor at the University of California, identified the first quake as the trigger that initiated the second one. This doublet effect compounded the devastation, resulting in over 2,200 fatalities and extensive property damage.

The Geographical Impact

Seismic waves from the initial quake expanded in all directions, though those heading east reached a critical juncture at the San Sebastián fault. This event activated the second tremor, with the rupture spreading more than 100 miles toward Caracas. According to William Barnhart from the United States Geological Survey, this eastward rupture maximized the quake’s impact on densely populated areas.

The primary rupture began along the Boconó fault, acknowledged for producing significant quakes in the past. Satellite images confirmed the second quake’s trajectory along the San Sebastián fault, explaining the extensive shaking experienced in Caracas.

Ground Displacement and Directivity

Scientists analyzed satellite data to assess how much the ground shifted post-quake. In regions like La Guaira, located near the fault line, the ground moved 1.5 feet westward. The San Sebastián fault’s strike-slip nature facilitates such horizontal movements.

“Directivity very likely contributed to the strong ground motion in Caracas and the area overall,” noted Dr. Oglesby.

Movement amplified seismic wave strength, affecting areas to the east. As waves gathered like an advancing wavefront, they increased shaking intensity, potentially rendering buildings irreparable.

Shallow Depth Concerns

The quakes originated just six miles below the surface, translating to powerful ground shaking. Vitor Silva of the Global Earthquake Model Foundation explained that shallow quakes cause more significant surface disruptions, akin to a shallow explosion. The proximity of energy release points to populated areas magnified destruction.

This shallow activity extended impact through soft, sedimentary surfaces that amplified seismic waves. The result was strong tremors in areas like Caraballeda and other coastal cities, reaching far from the epicenter.

Unconsolidated Soil Influence

The seismic impact was exacerbated by the geological makeup of the region. Areas like Caraballeda are built on flat, sedimentary zones, which can worsen the effects of seismic waves. Soft soil tends to amplify shaking if it resonates with a building’s natural swaying frequency. Understanding these factors is crucial for constructing resilient structures in quake-prone areas.

Reports indicate at least 152 buildings were destroyed in Caraballeda, primarily on unconsolidated soil. High-rise collapses were prevalent along the coastline, illustrating the destructive power of the fault lines in soft soil areas.

Building Standards and Compliance

Venezuela’s building codes are respected in Latin America for their thoroughness. However, the scale of destruction suggests that many structures didn’t adhere to these standards. Although a comprehensive study is pending, it’s suspected some builders ignored codes, leading to weakened buildings.

Soft stories—lower floors with insufficient structural support—contributed to collapses. Some buildings showed structural defects, with columns failing due to inadequate steel reinforcement. Older constructions might not have met updated standards, raising concerns about building integrity and safety.

While some buildings stood with internal damage, allowing occupant escape, others collapsed entirely. Engineers must focus on updating and following building standards to prioritize both human survival and structural integrity moving forward.