Scientists are warning residents of Vancouver and other cities in earthquake zones to take heed of new evidence that megaquake aftershocks can pose a great danger for years, even hundreds of kilometres from the epicentre of the original earthquake.

Even though Greater Tokyo is located 400 kilometres from the epicentre of the devastating magnitude 9.0 earthquake that struck Japan’s east coast in March 2011, the incidence of smaller earthquakes in the city of 36 million people jumped 10-fold after the megaquake, say U.S. and Japanese seismologists in an article in the journal Science Thursday.

Today, two years later, the rate of earthquakes in Tokyo is three times higher than it was before the megaquake, likely because of the stress caused by the relatively distant quakes on the fault located beneath Tokyo.

Santiago, Chile, saw a similar increase in earthquakes after the February 2010 magnitude 8.8 megaquake, which was also 400 kilometres away.

“Aftershocks just one magnitude smaller than their main shock are common, and there is a small probability that an aftershock will be larger than its main shock,” wrote Ross S. Stein of the U.S. Geological Survey and Shinji Toda of Tohoku University. ”Thus, they cannot be dismissed as harmless.”

The authors noted that Tokyo and Santiago have each been nearly destroyed twice by earthquakes since being founded around 1600.

“Other great cities within reach of earthquakes, such as Vancouver, Taipei, Manila, Lima, and Jakarta, could suffer a similar fate,” they warned.

Megaquakes assumed to reduce subsequent risk

The recent findings about aftershocks haven’t yet been incorporated into national assessments of earthquake risk, Stein and Toda note.

In fact, models used to assess earthquake risk usually assume that a megaquake reduces the risk of subsequent earthquakes by relieving accumulated stress on the fault at the epicentre, they said.

They hope that will change with the launch in 2014 of an open model of earthquake risks and consequences called the Global Earthquake Model.

The researchers suggested that better post-earthquake monitoring and modelling based on the results is needed around the world in order to help scientists understand whether the increased rate of earthquakes in cities like Tokyo after a megaquake some distance away means that a large quake is more likely to hit the city itself.

“Without this knowledge,” they added, “governments will be reluctant to act.”

Also on HuffPost:

Loading Slideshow...
  • A worker checks radiations on the window of a bus at the screening point of the Fukushima Dai-ichi nuclear plant at Okuma in Fukushima prefecture Wednesday, June 12, 2013. (AP Photo/Toshifumi Kitamura, Pool)

  • Workers move bags of contaminated earth at a collection site after a decontamination operation at Naraha town in Fukushima prefecture on June 13, 2013. (TOSHIFUMI KITAMURA/AFP/Getty Images)

  • In this Wednesday, June 12, 2013 photo, the crippled Fukushima Dai-ichi nuclear power plant is seen through a bus window in Okuma, in Fukushima prefecture. (AP Photo/Noboru Hashimoto, Pool)

  • Kansai Electric Power Co. senior official Ikuo Morinaka, left, leaves a press conference held after he filed applications for safety inspections by the Nuclear Regulation Authority (NRA), in Tokyo, Monday, July 8, 2013. (AP Photo/Koji Sasahara)

  • In this June 12, 2013 file photo, workers in protective gear walk past thousands paper cranes at the emergency operation center of tsunami-crippled Fukushima Dai-ichi nuclear power plant, in Okuma in Fukushima prefecture. (AP Photo/Noboru Hashimoto, File)

  • In this June 12, 2013 file photo, the steel structure for the use of the spent fuel removal from the cooling pool is seen at the Unit 4 of the Fukushima Dai-ichi nuclear plant at Okuma in Fukushima prefecture, Japan. (AP Photo/Noboru Hashimto, File)

  • A worker cleans the surface during a decontamination operation at Naraha town in Fukushima prefecture on June 13, 2013. (TOSHIFUMI KITAMURA/AFP/Getty Images)

  • Bags of contaminated earth are stored at a collection site after a decontamination operation at Naraha town in Fukushima prefecture on June 13, 2013. (TOSHIFUMI KITAMURA/AFP/Getty Images)

  • A worker, left, checks radiations on the window of a bus during a press tour, at the screening point of the Fukushima Dai-ichi nuclear plant in Okuma, Fukushima prefecture Wednesday, June 12, 2013 (AP Photo/Noboru Hashimoto, Pool)