The twin earthquakes that struck Venezuela on June 24—which have so far claimed almost 2,300 lives, with thousands of others still unaccounted for amid the rubble—have led to unfounded concerns about violent seismic events becoming globally more common. The worries are based on a series of seismic events taking place over the past few months from Afghanistan to the Pacific Rim. Although seismologists have debunked the dot-joining efforts, the Venezuelan catastrophe has yielded more serious worries about twin earthquakes—doublets, which involve two strong quakes of similar intensities striking the same region in quick succession, compounding death and destruction. In the South American nation, the two tremors were separated by a mere 39 seconds.
Doublets are rare, but five of them have been recorded over the last seven decades—in New Zealand’s Taranaki region in March 1960; in California in November 1987, when two quakes occurred in a farming region about half a day apart; in Pakistan in February 1997, when two strong quakes struck Balochistan just 19 seconds apart; in Iran in August 2012, when the East Azerbaijan province was rocked twice within minutes; and in Turkey and Syria in February 2023, when quakes of magnitudes 7.8 and 7.5 struck nine hours apart. Seismologists say doublets defy Bath’s law, which follows Swedish seismologist Markus Bath’s 1965 observation that the largest aftershock is typically about 1.2 magnitudes smaller than the main one.
India needs to be wary about doublets as seismologists consider the Himalayan range one of the world’s most seismically volatile regions. The boundary where the Indian tectonic plate grinds against the Eurasian plate creates immense stress in the Earth’s crust. This pressure props up the Himalayas and causes numerous faultlines, where a rupture in one fault can quickly trigger another in a connected fault, contributing to a devastating doublet in this fragile ecosystem.
The possible impact of such a doublet cannot be ignored, considering that over 40 percent of India’s population lives in the Upper Indo-Gangetic Plain—the food bowl of the country—and the Northeast region, both vulnerable to severe seismic events. To begin, we need to understand the operating procedures that would kick in if such a tragedy strikes. As Venezuela is reminding us, the first steps following a doublet are the most critical ones.