An earthquake in Peru earlier this year produced significant ground shaking in highland regions of the country. It set off a wave of panic that glacial lakes in the Andes might burst their banks and create devastating floods.
The quake, of magnitude 5.3 on the Richter scale, took place at 1:42am local time on January 28. As reported by the U.S. Geological Survey’s Earthquake Hazards Program, its epicenter was located under the Pacific Ocean, about 55 kilometers from the port of Chimbote in the region of Ancash, where the shaking was most instance. It was felt up and down the coast, as far north as Trujillo and as far south as Lima. The tremors also extended inland.
This earthquake was the first of a cluster. The second occurred five hours later in the town of Ica to the south of Chimbote. The third took place two hours after that, near Arequipa, still further to the south. These were smaller—4.7 and 4.4, respectively—but close enough in time to create a stir in the media, with extensive coverage all day long in national media. Moreover, Peru had experienced mudslides and debris flows in the months before the earthquake, adding to the sense of concern.
— Noticias24 Carabobo (@N24_carabobo) January 28, 2017
The first earthquake was a source of great concern in the highland areas closest to Chimbote, particularly in the Callejón de Huaylas—the long valley along the Santa River, just below the Cordillera Blanca, the mountain chain which contains the largest area of glaciers in Peru. The regional capital of Huaraz and several other sizable towns are located in this valley, which has experienced a number of destructive glacier lake outburst floods. Christian Huggel, a Swiss glaciologist who was working in the area at the time, wrote, “We felt the earthquake here in Huaraz during the night.” He added, “I did not see any damage in the morning, so everything seems to be okay around here.”
Benjamin Morales, the director of Peru’s National Institute for Research on Glaciers and Mountain Ecosystems, told GlacierHub that “the heavy rainfall and landslides in central and southern regions [of Peru]” added to the concern following the earthquakes, sensitizing the whole country to the risk of natural hazards even though risks were not as severe in Ancash and north of the country, where, he said, “rainfall is lower.”
Tony Oliver-Smith, an anthropologist at the University of Florida with extensive experience in the region, indicated to GlacierHub that the timing of the events, in the middle of the rainy season, was significant. He wrote, “Those of us who have worked in the Callejon de Huaylas are always alert to the effects of earthquakes and landslides, particularly in the rainy season,” when soils are moist, and more likely to erode.
The greatest fear was in Carhuaz, a provincial capital to the north of Huaraz. It lies near Huascaran, the tallest peak in the Cordillera Blanca, and the site of one of the world’s largest glacier lake outburst floods in 1970. This event, triggered by an earthquake, led to a debris flow which covered the town of Yungay, with about 6,000 fatalities.
A series of smaller aftershocks which followed the main earthquake kept the tensions high in Carhuaz. A Peruvian newspaper, Primera Página, reported that people were concerned that “blocks of ice would detach from glaciers and fall into the lake.” The resulting waves could overtop the rock walls that rim the lake and create a flood.
The residents of Carhuaz were also aware that the town had become more vulnerable to floods. A few months earlier, villagers had vandalized equipment that had been installed at a high mountain lake, called Laguna 513, directly above the town. The instruments, brought to the region at significant expense, were designed to provide warnings if the lake destabilized and threatened to flood the settlements below. As Morales, Huggel and other sources told GlacierHub, the reasons for this destruction are still not clear; they could have involved distrust of foreigners involved in the project, or beliefs that local spirits were offended by the equipment, or simply rivalry between different political factions.
A recent video offers testimony to the damage at the site:
Whatever the precise motivation of the people who attacked the warning system, the timing of the earthquake, coming soon after it was disabled, added to the concern. Primera Página reported that people felt “unprotected.” Cesar Portocarrero, a Peruvian glaciologist who lives and works in the region, wrote to GlacierHub, “In Carhuaz they felt the shaking and of course they immediately thought about the lake where the early warning system had been completely destroyed. It is very sad that the instruments were taken away.”
In the weeks after the earthquake, the aftershocks abated and concerns diminished. Patricia Hammer, an anthropologist who lives outside Carhuaz, wrote to GlacierHub in February of the “tremor,” saying that it left “little impact here in the highlands.” Nonetheless, the region remains vulnerable to earthquakes and floods. The challenges in establishing locally acceptable warning systems make these risks even greater.