Magnitude 7.5 quake follows 7.2 temblor in Venezuela within 39 seconds

A magnitude 7.2 earthquake struck Venezuela on Wednesday evening, followed 39 seconds later by a magnitude 7.5 event. The back-to-back quakes killed more than 900 people and flattened numerous structures. Seismologists described the sequence as a doublet, an event in which two quakes of similar size occur within minutes to days of each other.

The short interval between the two main shocks left little time for residents to react before the stronger second tremor arrived.

Doublet definition and past examples A doublet involves two earthquakes in the same seismic sequence that fall within 0.4 magnitude units of each other. Some researchers use a broader definition that includes events separated by hours or days. Past doublet sequences include a 1992 California event and a 2019 Ridgecrest sequence in which a magnitude 6.4 quake preceded a magnitude 7.1 shock by about 34 hours.

A 2023 quadruplet sequence in western Afghanistan produced four magnitude 6.3 quakes over one week and killed 2,400 people.

Venezuelan damage and building resilience More than 900 people died in Venezuela and countless buildings collapsed. Officials issued an unprecedented public warning after the doublet struck.

“Caution should be taken that that building could get worse from an aftershock." — Maria Mohammed, president of the Structural Engineers Assn. of Southern California A damaged structure is not as strong as before the first quake, increasing risk during subsequent shaking. The Venezuela sequence is expected to draw renewed attention to building codes and infrastructure resilience.”

California planning and fault interactions Researchers have modeled a hypothetical doublet on the Newport-Inglewood and Palos Verdes faults that could produce magnitude 7.25 and 7.05 quakes hours apart. A separate scenario under study involves a magnitude 7.8 San Andreas event followed by a magnitude 7 quake on the Hollywood and Raymond faults.