The recent seismic doublet that occurred in Venezuela reactivated the debate on seismic risk in Latin America and highlighted the vulnerability of cities to large-scale events.
In Argentina, the National Institute of Seismic Prevention (INPRES) updated the national seismic hazard map in 2022, after four decades, incorporating new technologies and monitoring data.
Classification of seismic zones in Argentina
The Argentine territory is organized into five hazard levels, from zone 0 (very low risk) to zone 4 (maximum risk):
- Zone 4 (very high hazard): south of San Juan and north of Mendoza, including their capitals.
- Zone 3 (high hazard): center of Mendoza, north and east of San Juan, west of La Rioja, and northwest of San Luis.
- Zone 2 (moderate hazard): north of Salta and Jujuy, Tucumán, Catamarca, west of Córdoba, northeast of Chubut, and part of Tierra del Fuego.
- Zone 1 (reduced hazard): center and north of Tierra del Fuego, south of San Luis, west of La Pampa, and sectors of Mendoza.
- Zone 0 (very reduced risk): Buenos Aires, Entre Ríos, Corrientes, Misiones, a large part of Formosa, Chaco, and Santa Fe.
The map shows that there are no longer areas of zero risk: all provinces present some level of seismic threat, including urban centers far from the mountain range.
Argentine seismic history
The most destructive earthquakes were concentrated in the central-west of the country:
- Mendoza 1861: destroyed the city and caused thousands of casualties.
- San Juan 1944: considered the greatest national seismic tragedy, with around 10,000 deaths.
- San Juan 1977: a seismic doublet was recorded, with two earthquakes separated by just 30 seconds.
These antecedents show that the Andean region is the most exposed and that complex phenomena such as seismic doublets are possible in Argentina.
Geological origin and active faults
Earthquakes in Argentina originate from faults in the South American Plate, highly fractured in the Andean region bordering Chile. The interaction with the Nazca Plate generates tectonic stresses capable of activating deep and surface faults.
INPRES defines a fault as a fracture in the Earth’s crust where blocks of rock move. When the accumulated tension exceeds a limit, the release of energy produces an earthquake. Active faults are those that have moved in recent times and are associated with the most significant earthquakes.
Risk of seismic doublet
Geologist Andrés Folguera, a researcher at Conicet, explained in an interview with Infobae that a doublet occurs when a first earthquake modifies tensions and activates a neighboring fault.
It is not a replica, but two main events of similar magnitude. Although the probability is low, the precedent of San Juan 1977 shows that it is possible in Argentina.
Prevention and regulations
INPRES maintains that, although it is not possible to predict an earthquake with precision, updating maps and constant monitoring allow for improved prevention. The key lies in:
- Seismic-resistant regulations: construction adapted to risk zones.
- Public education: dissemination of self-protection measures.
- State intervention: regulation of public and private buildings.
The Venezuelan experience shows that, in the presence of a doublet, both the response capacity and the resilience of the infrastructure are put to the test.
Argentina presents a diversity of seismic risks, concentrated in the northwest and central-west.
The national seismic history and recent international episodes underline the need to maintain monitoring, reinforce construction regulations, and educate the population to reduce the impact of future events.
