Very strong and shallow M6.4 earthquake hits San Juan, Argentina


A very strong earthquake registered by the USGS as M6.4 hit San Juan, Argentina at 02:46 UTC (23:46 LT) on January 19, 2021. The agency is reporting a depth of 20 km (12.4 miles). EMSC is reporting the same magnitude and depth.

The epicenter was located about 29 km (18 miles) WSW of Pocito (population 40 969), 43 km (27 miles) SW of San Juan (population 447 048), 45 km (28 miles) SW of Santa Lucia (population 43 565), and 46 km (29 miles) SW of Villa Paula de Sarmiento (population 19 092), Argentina.

There are about 750 000 people living within 100 km (62 miles).

1 000 people are estimated to have felt very strong shaking, 651 000 strong, 216 000 moderate, and 6 561 000 light.

Image credit: TW/SAM, Google

The USGS issued a yellow alert for shaking-related fatalities. Some casualties are possible and the impact should be relatively localized. Past events with this alert level have required a local or regional level response.

A green alert was issued for economic losses. There is a low likelihood of damage.

Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. The predominant vulnerable building types are adobe block and rubble/field stone masonry construction.

Recent earthquakes in this area have caused secondary hazards such as landslides and liquefaction that might have contributed to losses.

The quake was followed by a series of aftershocks, including M5.0 at 03:03 UTC, M4.9 at 03:08 UTC, M5.3 at 03:37 UTC, M4.9 at 03:51 UTC, and M4.8 at 04:01 UTC.

The governor of San Juan urged people to stay calm and 'put into practice all the measures that we have learned to prevent incidents.'

Initial reports mention houses damaged in the small town of Media Agua, damaged roads, power outages, and injuries.

There are currently no reports of casualties or serious damage.

Estimated population exposure to earthquake shaking

Selected cities exposed

Regional seismicity

Featured image credit: TW/SAM, Google


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