9 November 2018

Landslides from the M=6.7 6th September 2018 Hokkaido Iburi-Tobu Earthquake – a first technical report

Posted by Dave Petley

Landslides from the M=6.7 6th September 2018 Hokkaido Iburi-Tobu Earthquake – a first technical report

On 6th September 2018 a M=6.7 earthquake struck Hokkaido in Japan. This event, now known as the Hokkaido Iburi-Tobu Earthquake, was remarkable for the number of landslides that it triggered. I posted extensively about it at the time, and thereafter. The journal Landslides has an initial short report about the landslides triggered by this event (Yamagishi and Yamazaki 2018).  The key points that they note include:-

  • Landslides claimed 36 lives out of a total of 41 fatalities in total, thus representing the most significant impact of the earthquake.
  • Landslides were triggered over a 20 x 20 km area in the vicinity of Atsuma Town.
  • To date over 6,000 landslides triggered by the earthquake have been mapped.
  • Interestingly however, only about 1,000 debris deposits have been identified.  Whilst this might seem paradoxical, it is a sign that many of the landslides combined to form a single, complex deposit.
  • Most of the landslides were shallow failures, with a planar or spoon-shaped rupture surface.
  • Most of the landslides occurred in airfall ash and pumice layers, typically 1.5 m thick, erupted from Tarumai volcano at about 9000 years BP.

The authors speculate that the large number of landslides triggered by this earthquake was a result of the vulnerability of the local geology to seismically-induced triggering, possibly compounded by high groundwater levels as a result of the recent passage of Typhoon Jebi, which had deposited over 100 mm of rainfall in the preceding three days.

Hokkaido Iburi-Tobu Earthquake

Planet Labs image showing landslides triggered by the 6 September 2018 M=6.7 Hokkaido Iburi-Tobu Earthquake. 4-band Planetscope image collected on 20th October 2018, used with permission.



Yamagishi, H. & Yamazaki, F. 2018.  Landslides by the 2018 Hokkaido Iburi-Tobu Earthquake on September 6. Landslides. https://doi.org/10.1007/s10346-018-1092-z

Planet Team (2018). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/