The number of earthquakes has increased throughout Ecuador in recent months, including those felt in Cuenca and the southern sierra region. According to the Austro Seismic Network at the University of Cuenca, the number of perceptible earthquakes in Azuay, Cañar and Loja Provinces has increased from 4.13 in March to 5.46 so far in July.
Henry Bermeo, director of the Seismic Network says that the monthly count is based on earthquakes above 3.0 on the Richter scale. “Below that range, the events are generally not felt beyond a few kilometers of the epicenter and then, only if they are relatively shallow.”
Bermeo said all except two of the earthquakes felt in Cuenca and Azuay Province occurred outside of the province. “Two were centered in the Cajas Mountains, in January and May, but they were 3.1 and 3.2 magnitude and were not felt in most of the province,” he says.
According to geologic surveys conducted by the University of Cuenca and the U.S. Geologic Survey, Azuay Province and most of the southern sierra are at lower risk for major earthquakes. “The region is composed of older, more stable geologic structures and is less susceptible to major seismic movement than other areas of Ecuador,” the USGS said in 1997 report. “The Cajas Mountains are one the oldest outcrops of the Andes mountain chain, and hence, more stable.”
Bermeo points out, however, that the Cuenca area is still at risk for damaging earthquakes. “There are at least two geologic faults in the area, one beginning near Girón and running north past Cuenca to the west, another east of the city, near Paute.” He says earthquakes in 1887 and 1893 that caused widespread damage in Cuenca were probably associated with the two faults.
According the USGA, the 1887 and 1893 quakes had an estimated magnitude of between 4.7 and 5.1. Bormeo says events of that magnitude or greater will inevitably occur again. “Even though this area is at lower risk of catastrophic earthquakes, such as those that have occurred on the coast, we are still within an active seismic zone where continental plates collide and should always be prepared.” He added that it “very worrisome” that an estimated 60 percent of structures in Azuay Province do not meet the modern earthquake construction code.
He adds that he also worries that not enough attention is given to earthquake preparation in the province. “Planning for a possible disaster should be an ongoing effort, not one that gets attention only after a major earthquake, like the 2016 event.”
The historic record shows that Ecuador’s coast is the most vulnerable area for major earthquakes, with a potential for quakes of 9.0 in magnitude or greater. A 1906 quake, centered near Esmeraldas and estimated to be 8.8 to 9.1 in magnitude, killed hundreds in northern Ecuador and southern Colombia and caused a tsunami that killed residents of Hawaii and Japan. More recently, the April 2016 7.8 magnitude earthquake in Manabi Provivince killed 663 and destroyed thousands of structures.
In the sierra, earthquakes of magnitudes of 6.0 or greater have killed hundreds in Ambato and Quito and caused extensive damage.
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 government estimates that more than 80,000 people died in those quakes.