Widespread liquefaction hampers reconstruction after M7.6 earthquake in Ishikawa, Japan

Widespread liquefaction hampers reconstruction after M7.6 earthquake in Ishikawa, Japan

In the aftermath of the January 1 earthquake, the city of Wajima in Ishikawa Prefecture faces significant challenges due to liquefaction, severely impacting infrastructure and complicating relief efforts. Continuous aftershocks further hinder the restoration process, with houses, roads, and manholes notably affected. Governor Hiroshi Hase has requested a comprehensive investigation from the central government to address the escalating situation, emphasizing the need for seismic reinforcement of underground infrastructure.

In the wake of the January 1, 2024 M7.6 earthquake in Japan, the city of Wajima, located in Ishikawa Prefecture, has been severely impacted by liquefaction, a phenomenon that reduces the strength of soil due to seismic activity, particularly affecting coastal areas.

This has significantly hampered relief and restoration efforts in the region, with continuous aftershocks further complicating the situation. Liquefaction has led to visible and dramatic changes in the landscape, including protruding manholes, tilted or partially buried houses, and deformed roads.

Fumihiko Imamura, a professor at Tohoku University’s International Research Institute of Disaster Science, explains that liquefaction occurs when moisture in the soil breaks loose from grains of soil due to the shaking caused by an earthquake. This process can cause water to rise up, leading to the surfacing of sand on land and the elevation of manholes.

The phenomenon was not limited to Wajima but was also severe in cities like Suzu in Ishikawa, and extended across a wide area of the Sea of Japan coast, affecting regions from Uchinada near Kanazawa to Niigata and Joetsu in Niigata Prefecture. Notably, during the Great East Japan Earthquake in March 2011, areas far from the epicenter, such as reclaimed land in Urayasu, Chiba Prefecture, also experienced liquefaction, indicating the widespread potential for this phenomenon.

Ishikawa’s Governor, Hiroshi Hase, called for a comprehensive investigation into the liquefaction phenomenon, especially in Uchinada, recognizing that the town requires support for such a large-scale study. The restoration of manhole covers and underground sewage pipes, which are critical for the area’s infrastructure, necessitates specialized repairs.

One of the overarching challenges highlighted by the earthquake’s aftermath is the lack of seismic reinforcement across many of Japan’s pipelines. As of the end of March 2022, out of 86 594 km of major pipelines requiring seismic reinforcement, only about 55% had been reinforced.

Imamura points out that Japan’s disaster response tends to be reactive, based on experiences from previous events. However, the unique challenges posed by liquefaction, which can overlap with other disaster types like earthquakes and tsunamis, demand a more proactive and prepared approach.

The reconstruction in the Tohoku region post-3/11 was accelerated by the tsunami’s cleansing effect, but the recovery from liquefaction presents a more complex challenge, requiring long-term efforts to solidify the ground and restore the affected areas fully.

References:

1 Quake-induced liquefaction hampers Noto reconstruction – The Japan Times – February 16, 2024

2 Liquefaction triggered by Noto Peninsula Earthquake causes extensive damage – NHK – January 23, 2024

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