Small recreational vehicle driving the Dempster Highway near Dawson City, Yukon, Canada. Credit – Robert Postma\/Design Pics Editorial\/Universal Images Group\u2014Getty Images<\/p>\n
High up in Canada\u2019s Yukon Territory, a seismic gun is being cocked and aimed at the little community of Dawson City\u2014population 1,600. If a new study<\/a> in the journal Geophysical Research Letters is correct, that town or one of many others in the region could be rocked by a major earthquake pretty much at any moment. The source of the danger is a 1,000 km (620 mi.) formation known as the Tintina fault that cuts northwest across the Yukon and terminates in Alaska. It has been mostly still for the past 12,000 years but appears to be getting ready to lurch to life.<\/p>\n \u201cOver the past couple of decades there have been a few small earthquakes of magnitude 3 to 4 detected along the Tintina Fault, but nothing to suggest it is capable of large ruptures,\u201d said Theron Finley, a recent PhD graduate at Canada\u2019s University of Victoria and the lead author of the study, in a statement. That\u2019s not the full story, though, Finley says. What the last few decades suggest and what the geological record now shows are two different things\u2014and according to the paper, Tintina is a lot more menacing than it seems.<\/p>\n What caught the interest of Finley and his colleagues is a 130-km (80 mi.) segment of the fault that runs near Dawson City, with surface features suggesting that numerous large earthquakes occurred in relatively recent geological history\u2014during the Quaternary Period, which runs from 2.6 million years ago to the present. To get a better understanding, the researchers used an existing library of high-resolution imagery from airplanes, satellites, and drones, some of them captured by lidar<\/a>\u2014which uses pulsed laser emissions to produce 3D maps of the surface. This allowed them to study that stretch of the fault in unprecedented detail\u2014and find a number of geological secrets hiding in plain sight.<\/p>\n At one point in the Tintina segment, they discovered a fault scarp\u2014or a ridged crack in the surface\u2014where the land broke and shifted by 1,000 m (3,280 ft.). That is a clear fingerprint of a long series of earthquakes, ones that, according to the computer models of the terrain, occurred about 2.6 million years ago. At another spot they found another scarp, misaligned by a more modest 75 m (250 ft.), that they estimate to have been caused by smaller but still considerable quakes that occurred about 132,000 years ago. No evidence of significant quakes turned up at any time in the past 12,000 years, meaning Tintina has been relatively stable throughout the entirety of the Holocene Epoch<\/a>, which runs from 11,700 years ago to the present.<\/p>\n But for modern day folks living in Dawson and elsewhere, that recent period of quiescence is actually bad news. Just because a fault isn\u2019t causing quakes doesn\u2019t mean it isn\u2019t on the move. Finley and his colleagues estimate that Tintina is moving and accumulating strain on the order of 0.2 mm to 0.8 mm a year. Over the course of 12,000 years, those millimeters add up, and when the strain is suddenly released\u2014which it ultimately must be\u2014the result will not be pretty.<\/p>\n “We determined that future earthquakes on the Tintina fault could exceed magnitude 7.5,\u201d said Finley in a statement. \u201cBased on the data, we think that the fault may be at a relatively late stage of a seismic cycle, having accrued a slip deficit, or build-up of strain, of six metres [20 ft] in the last 12,000 years. If this were to be released, it would cause a significant earthquake.\u201d<\/p>\n The estimated 7.5 magnitude of the quake would put it on a scale with some of history\u2019s bigger temblors, including China\u2019s 1976 Tangshan event<\/a> which claimed an estimated 240,000 to 650,000 lives; and the 2010 Haiti quake<\/a>, which killed 300,000. The Yukon Territory is much more sparsely populated than Tangshen or Haiti, meaning fewer casualties. Still, there would quite likely be deaths, along with damage to local highways, mines, and other infrastructure. The area is also prone to landslides which could be triggered by a quake.<\/p>\n \u201cOur results,\u201d the researchers wrote, \u201chave significant implications for seismic hazard in the Yukon Territory and neighboring Alaska. If 12,000 years have elapsed since the last major earthquake, the fault may be at an advanced stage of strain accumulation.\u201d<\/p>\n It is impossible to know exactly when that strain will be released, of course\u2014one of the things that makes seismology such a confounding science. The best the scientists can do is warn locals of the long term risks and leave them to prepare<\/a> go bags, survival kits, and evacuation plans. The Earth will quake at will; we can only react.<\/p>\n Corrections, July 30: The original version of this story misstated the year of the Haitian earthquake. It was 2010, not 2020. In addition, this story misstated how the age of scarps was determined. The researchers used computer modeling, not analysis of erosion. The article also incorrectly stated that individual earthquakes were responsible for the 1,000-meter and 75-meter misalignments in the ground. There were multiple quakes at both sites, not just one at each. <\/p>\n