The Chira Quake of 2021

A 6.1 magnitude event shook the whole Piura Department, and this is what the science knows up to now.

 

By Nelson Peñaherrera Castillo

 

Peru is SHAKING! Magnitude 6.1 Earthquake in Sullana, Peru - YouTube

 

SOJO, Peru – On July 30^th, 2021, noon, it was goin to be another winter-else, sunshine. Some people were inside their homes watching the Peru’s Bicentennial military parade that, due to Covid-19 pandemic, might have in a closed military facility at Lima City. Just ten minutes after the zenith (1710 GMT), the land under the capital of Miguel Checa District, Sullana Province, shook without a sense and violently.

 

At a spot, 25 miles under the surface of rock, sand, and pulverized clay, two huge pressing landmasses, maybe 3300 feet thickness, shocked one each other and started a list of focused events in a portion running from Marcavelica District, just the north of Miguel Checa, and going to the border of provinces Sullana and Piura, at the Curumuy agricultural place. It’s about a curve, at least 25 miles length.

 

According to Peru’s Geophysical Institute (IGP, as its initials in Spanish), the July 30^th event was a 6.1 momentum magnitude, and a VI (read ‘sixth’) calculated intensity for Sullana City, located 11 miles to the east of the epicenter, that ended to be somewhere on Chira River flow, where districts Miguel Checa, Marcavelica, and Ignacio Escudero join.

 

Around, aside Sojo, towns also affected were nearby Tangarará, Monterón (Marcavelica District), Santa Sofia (Ignacio Escudero District), and the not too nearby Jíbito (Miguel Checa District), already in Sullana Metropolitan Area. Next three weeks, about 25aftershocks, mostly fast-paced, magnitudes between 3.5 and 4.3 happened with epicenters encloistered in a land, 4 miles length by 0.6 miles width, near Chalaco Town (Miguel Checa District), 8 miles distance in straight line away the southwest of Sullana Downtown, according to a preliminary deduction based on data reported by IGP.

 

Despite the intensity and the mostly sandy soil over the Sullana Province’s capital city is settled down, damages were not greater than cracks in some cement buildings with bad designed beams, but at the epicenter zone, adobe (dry mud brick) walls broke up to down, and some brought down. The weakness of structures forced many people in Sojo to go out to the streets for spending the night.

 

According to Marcavelica’s Mayor Augusto Chiroque, 40% of buildings in Tangarará Town had some type of damage, including the local school, and another else’s fence, in nearby Santa Sofia [See the pictures down this story], felt down in sections. Tangarará is built on slimy soil, caused by the historic overflows of Chira River, but an additional phenomenon happens in Santa sofia – “the soil is salty,” Architect Raúl Montero observed.

 

According to Mr Montero, Santa Sofia school is built on the town’s lowland where the saltpeter tends to accumulate. As a constant effect, the substance corrodes the steel of beams, decreases balance, and the rest the gravity force itself can do it through the years… or a strong shake in a matter of seconds.

 

Although the effects of the quake or seism concentrated in the border of Chira Middle and Lower Valleys, they also affected many towns in La Huaca District including its capital, just 15 miles to the west of the epicenter, and further places as Chira River Delta, between districts Vichayal and Colán, about 40 miles to the west of the epicenter, or Catacaos District, where it’s affirmed there are damages in the store market at district’s capital, located other 40 miles to the south of the epicenter.

 

Plate tectonics and volcanism in South America - YouTube

 

Presummed guilty

The general explanation for this and other quakes happening not only across Piura Department but a coastal strip beginning in Chile and ending in Colombia is the subduction or embedding that the Nazca Plate, in Pacific Ocean, does under the South American Plate [watch the video above this paragraph], and what can check when every quake event is traced and it’s noticed that, preliminarily, as much eastern (toward the continent) it breaks, the hypocenter tends to be deeper. But according to IGP, the local cause targets to a fault running at the Piura north-occidental quadrant – Huaypirá.

 

It’s about a sliding fracture going 25 miles at the north of Sullana Metorpolitan Area doing a course, approximately 53 miles, in east-west direction, according to Geological, Mining, and Metallurgical Institute (ingemet as in Spanish), what approaching to the little Amotapé Range, within provinces Sullana, Talara (Piura Department), and Contralmirante Villar (Tumbés Department), diverts to the south.

 

According to geologists, this fault could influence in Amotapés formation, maybe the most ancient mountain structure across the department, but they are actually sure it participated in formation of polymetallic deposits in the so-called Lanconés-Eréo Basin, mostly volcanic origin, although evidence of that activity has not been detected since pre-historic times up to today.

 

According to Ingemet, Huaypirá Fault separates two geologically dissimilar land masses: the Cretaceous to the north and much tending to Amotapés, from the Cenozoic to the south, where the July-30^th quake zone is located, but that has seen relatively much active since 2014 with recurrent hypocenters in a point under the border of provinces Sullana and Contralmirante Villar, and other in the western portion of La Huaca District (just adjoining Miguel Checa), according to IGP’s records.

 

Will it happen again?

IGP’s CEO Hernando Tavera stated to Radio Cutivalú of Piura that although all seems to be connected to Nazca Plate subduction, unlike the events broken in Central & Northern Chile and Central & Southern Peru, that tend to be more violent (like Pisco, Peru, August 15^th, 2007), the most probable is that if another strong quake breaks in this area, its magnitude wouldn’t exceed 7.0, what doesn’t necessarily mean it could be 0.9 times stronger because the magnitudes don’t express an aritmethic increasing measure but logarithmic, much greater in proportions.

 

However, Chira Valley do have a timeline of quakes bigger than the magnitude forecasted by Tavera. On December 9^th, 1970, at 23:55 local time (0435, December 10^th, 1970, GMT) a 7.2 event shook almost all Peruvian Northern and Ecuadorian Southern. It’s estimated the epicenter located somewhere in Querecotillo District, which capital city is 8 miles to the north of Sullana Metropolitan Area.

 

The so-called Querecotillo quake left 40 casualties – Sojo, none. Although it’s a relieving balance, Mr Tavera and other specialists say, judging the conduct of the population and its authorities, nothing has been learned in terms of prevention due to the people participate few or not in the drills that are held periodically, especially after Pisco Earthquake (2007). The true fact is that not only in Chira Valley but across Piura Department, aside living together with El Niño events, those come from the sea and the sky, we also have to live together with the quakes, those come from inner Earth.

 

Track the quakes in Piura Department and across Peru (official source).

 

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