Background: On September 6th, 2018, at 3:07 local time, a strong earthquake of magnitude Mw = 6.6 struck the east Iburi region in Hokkaido, Japan. Many serious damages such as landslide, liquefaction and collapse of houses occurred from this earthquake. Liquefaction caused road deformation and inclination of houses in Sapporo city, Hokkaido. In order to understand the damage caused by the earthquake, and find a solution to mitigate the liquefaction-induced damage in Sapporo city, a preliminary investigation of the 2018 Hokkaido Iburi-tobu earthquake was conducted from 18 to 20 September 2018. Results: The damages to the houses at Satozuka town and Utsukushigaoka town in Sapporo city are focused on. The damage at Satozuka was so enormous that the residents could not continue to live in their houses. Although the inclination of houses can be seen by visual inspection at Satozuka, there were few houses where the inclination can be judged visually at Utsukushigaoka. Therefore we did a field survey of inclined houses by using a digital angle meter at Utsukushigaoka. Conclusions: The inclination of 57 houses at Utsukushigaoka was measured, and the maximum value and direction of inclination are shown on the map. The houses located at the reclaimed land of the former river and former valley plain were inclined. Therefore, the old terrain greatly affected to the inclination of houses. These liquefactioninduced damage occurred in the same area where liquefaction occurred during the 2003 Tokachi-oki earthquake.

Background: In April 2016, Kumamoto City, Japan, and its surroundings were hit by a sequence of strong and devastating earthquakes including two significant events, one on April 14 th , 2016, at 21:26 JST (Mw6.2) and the other on April 16 th , 2016, at 01:25 JST (Mw7.0). These disasters caused 120 fatalities (including indirect fatalities), 2337 people injured and 177,914 residential houses were damaged. This paper aims to ascertain the damage to residential houses and buildings caused by liquefaction during this earthquake and suggests possible mitigation methods. Results: Field reconnaissance was conducted in the target area on May 27 th-30 th , 2016. The post-earthquake inclination angle and the tilt direction of 68 affected houses and buildings in the liquefied sites in Kumamoto City were measured by using a laser rangefinder (Leica DISTO D 510). Ground structure and condition were also determined from topographic maps, bore data and the calculated liquefaction resistance factor, F L. Conclusions: Based on this investigation, the inclination angle of the houses in the target area seems to be related to the type of building structure and their foundation as well to the local ground composition. The tilt direction has a tendency to be associated with the location of the nearby river. The results presented could be useful to develop future liquefaction mitigation measures for detached residential houses.

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This paper is focusing on the geo-disasters induced by the 2018 Hokkaido Iburi-tobu earthquake in Japan and the 2018 Sulawesi earthquake in Indonesia. The Hokkaido Iburi-tobu earthquake occurred at east of Iburi region in Hokkaido, Japan on September 6th, 2018. Tremendous number of landslides occurred in the mountain areas at Iburi region. Uplift and sinking of road and inclination of houses were caused by liquefaction in the south eastern part of Sapporo city. The Sulawesi earthquake happened at Central Sulawesi Province, Indonesia on September 28th 2018. The ground displacement triggered by the fault movement caused damage to roads and houses. The large scale ground flows induced by liquefaction occurred in some different sites. This paper reviews the damage induced by the geo-disasters and considers the lessoned learnt from the damaging earthquakes happened in 2018.

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