By Liam Higgins
According to the record, the deadly 7.8 magnitude earthquake that struck Ecuador’s northern coast is a once-every-50-to-100-year event. The quake killed more than 600, destroyed or severely damaged 45,000 structures, and left 30,000 people homeless.
“This was an earthquake of historic proportions,” said Alexandra Alvarado of Ecuador’s Geophysical Institute. “It’s terrible power reminds us that we must always be prepared in Ecuador, especially on the coast. This is the area that is most prone to large earthquakes due to the subduction zone between continental plates,” she says.
So, what is the vulnerability of other areas of Ecuador to powerful earthquakes? Are Quito or Cuenca at risk for a “big one” of their own?
The historic record and modern research show that vulnerability varies significantly from one part of the country to another. The coast is more vulnerable than Quito, for example, and Quito is more vulnerable than Cuenca.
Ecuador lies on the eastern rim of the seismically active area known as the Pacific Ring of Fire. There have been at least 38 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 people died in those quakes.
It is important, officials say, that residents know the level of risk of the areas where 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 higher risk include the northern Andes, including the cities of Ibarra, Ambato, Riobamba and Quito. The area of lowest risk is the far-eastern portion of the Ecuador’s Amazon region.
An overview of relative risk is shown in a earthquake risk map developed by the U.S. Geological Survey. The USGA is currently revising the map based on data collected in the 2016 earthquake. A USGA spokesman said that, based on information gathered after 2016, the extreme danger zone will be extended south on the coast to include the Santa Elena peninsula.
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 powerful 2014 quake in Chile.
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The town of Pedernales, the epicenter of the 2016 earthquake, suffered a 7.8 quake in 1942 but, because of the quake’s depth and lack of population in the area at the time, no deaths were reported
Several other strong earthquakes have occurred near the Ecuador-Colombian border during the last century. A powerful 8.2 earthquake 20 miles north of the border generated a tsunami in 1979 killed an estimated 400 people, mostly in Colombia.
Another powerful earthquake, measuring 7.2, hit 80 miles south of the 2016 quake, in 1998, devastating Bahia de Caraquez. Sixteen years later, many buildings in Bahia still showed the scars of that quake when the 2016 quake occurred.
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. Ambato still shows damage from a 1949 quake that registered 6.8 magnitude and killed more than 5,000.
“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 some of the coast, the coast is actually much more vulnerable,” says Yepes. “Not only will the quakes there be of greater magnitude but because they often occur offshore, there is a risk of tsunamis.”
According to Yepes and Geophysical Institute records, 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 geology and are consequently less seismically active. Cajas National Park, to the west of Cuenca, is one of the oldest regions of the Andes mountain chain.
Institute officials say that Cuenca has seen a number of earthquakes over the years estimated in the 3.9 to 4.2 magnitude range, the most recent in 2010. The strongest, estimated at 4.2, occurred in 1885 and destroyed several mud structures in the historic district. “Since the Spanish arrived almost 500 years ago, Cuenca has probably not had an earthquake above the mid-4’s magnitude,” says Yepes. “This is why so many of its historic buildings remain intact.”