Quito earthquakes prompt review of preparedness; Cuenca is at lower risk while the coast is at highest risk

As strong earthquake aftershocks continue to plague Quito and the surrounding area, Quito Mayor Mauricio Rodas urged residents to avoid attending public events as well as unnecessary travel on roads prone to landslides. Quito experienced 4.7 and 4.0 aftershocks on Saturday and Sunday. Saturday’s quake injured 13, one critically.

Among the events cancelled over the weekend were the games of Quito’s two professional football teams.

The high number and strength of the aftershocks following Tuesday’s 5.1 earthquake, prompted a joint press conference on Saturday with Rodas and President Rafael Correa. As of Sunday afternoon, there had been almost 90 measurable aftershocks.

Correa said that the government was learning a hard lesson in earthquake preparedness. “This event is unprecedented in terms of aftershocks and has reminded us that we must strengthen our responses,” he said. He added that he has instructed the country’s interior ministry to strengthen building codes, saying that 70% of structures in Quito are not strong enough to withstand a major earthquake, which he described as 6.7 or higher on the Richter Scale.

Correa said he has also instructed the country’s emergency agencies to reevaluate procedures and be prepared to respond to disasters similar to those suffered in Haiti, Peru and Chile in the last five years. “We have to be ready for catastrophic destruction,” he said.

How vulnerable is Ecuador to a catastrophic earthquake? Very vulnerable, according to the historic record.

The country lies on the eastern rim of the seismically active area known as the Pacific Ring of Fire, according the Ecuador’s Geophysical Institute. There have been at least 37 earthquakes estimated to be of magnitude 7 or higher on the Richter Scale since 1541, when written records by the Spanish were first kept, the institute says. The government estimates that more than 80,000 died in those quakes.

It is important, officials say, that residents know the level of risk of the areas in which they live. For example, Manta is at high risk for a catastrophic earthquake whereas Cuenca is at relatively low risk. Countrywide, the area of greatest risk, says the institute, is the coast, particularly the area from Manta to the Colombian border. Other areas at high risk include the northern Andes, including the cities of Ibarra, Ambato, Riobamba and Quito.

One of the six most powerful quakes in history struck the northern coast of Ecuador in 1906, killing 2,000 near Esmeraldas and sending a tsunami across the Pacific Ocean that killed hundreds more in Hawaii and Japan. The quake measured 8.9 on the Richter scale, equaling the recent quake in Chile. Another killer quake, measuring 7.3, hit a hundred miles to the south in 1999, devastating the town of Bahia de Caraques. Thirteren years later, many buildings in Bahia still show the scars of that quake and a number of buildings still stand abandoned.

In the Andes, Riobamba, Ambato and Ibarra have been destroyed by large earthquakes in the 19th and 20th century while Quito has suffered serious damage on three occasions before last week’s quakes. Ambato is still rebuilding from a 1949 quake that registered 7.1 magnitude.

“No area of Ecuador is entirely free from danger except for the eastern Amazonia,” says Institute director Hugo Yepes, “but we know that some areas, because of geology and geography, are in much more danger than others and that is where we need to focus our attention. Even though we put the Northern Andes in the same zone as the coast, the coast is actually much more vulnerable,” says Yepes. “Not only will the quakes there be of greater magnitude but because they usually occur offshore, there is a risk of tsunamis.”

According to Yepes and the institute, the area least vulnerable to earthquakes, outside of the Amazon, is the southern Andes. “In recorded history, Cuenca has not suffered a destructive earthquake and it has been more than 400 years since Loja has seen serious damage.”

Yepes explains that the southern Andes are older, with more settled mountains and consequently less seismic activity. “It is very important to understand,” Yepes cautions, “that all of Ecuador, including the southern Andes, is vulnerable and we must remain vigilant.”

Institute officials say that Cuenca has seen a number of earthquakes over the years in the 4.2 to 4.5 magnitude range, the most recent in 2008. “Since the Spanish arrived almost 500 years ago, Cuenca has probably not had an earquake above 4.5 or 4.6 magnitude,” says Yepes. “This is why so many of its historic buildings remain intact.”

Photo captions: USGS earthquake risk map for Ecuador; Debris falls on highway north of Quito following an aftershock (Credit: El Comercio)