M7.5 Japan Earthquake (01/01/2024) Aftermath and Report

A strong magnitude 7.5 earthquake hit 7 km (4.3 mi) north-northwest of Suzu, located on the Noto Peninsula of Ishikawa Prefecture, Japan, on January 1, 2024, at 15:10 local time. The Japan Meteorological Agency (JMA) officially named this earthquake the 2024 Noto Peninsula Earthquake (Reiwa 6-nen Noto-hantō Jishin 令和6年能登半島地震. The earthquake and its aftershocks caused widespread damage, numerous injuries, and 232 fatalities. Additionally, it triggered Japan's first major tsunami warning since the 2011 Tōhoku earthquake with waves expected to reach 3 m (9.8 ft). Nevertheless, a tsunami measuring over 1.2 m (4 ft) was recorded along the Sea of Japan.

In this blog post, we will dive deep into the earthquake's origin, and aftermath, as well as add Quantectum’s report.

M7.5 Japan Earthquake Origin (January 1, 2024)

Japan is situated at the converging borders of the Pacific, Philippine Sea, Okhotsk, and Amurian Plates. On the eastern and southeastern coasts of the island arc, the Pacific and Philippine Sea Plates undergo subduction at the Japan Trench and Nankai Trough, respectively. On the western coast of Honshu, which borders the Sea of Japan, a convergent boundary extends north to south between the Amurian and Okhotsk Plates. There is a suggestion that this area might be an emerging subduction zone characterized by eastward-dipping thrust faults.

The geological process of rifting followed by inversion has generated a series of coastal faults with the potential to induce earthquakes ranging from Mw6.8–7.9, often accompanied by tsunamis. Among these faults, one particularly noteworthy fault, designated as F43 in the comprehensive list of 60 meticulously evaluated faults, extends to the seafloor just north of the Noto Peninsula, trending WSW–ENE. This distinctive fault, characterized by a southeastward dip, consists of two segments with a combined length of 94.2 km (58.5 mi) and is deemed capable of triggering strong earthquakes. It also triggered the magnitude 7.5 earthquake in Japan on January 1, 2024.

The earthquake and its aftershocks were followed by a fire, which occurred in Wajima around 17:00. Due to damaged roads, firefighters were unable to extinguish the flames, which consumed an estimated 200 buildings, including many homes.

Picture 1: A man looks at the burnt area, following earthquakes in Wajima, Ishikawa prefecture, Japan. Source: @gulftoday

Tsunami Generated by the M7.5 Noto Earthquake

Large parts of Japan's western coast, from Hokkaido to Nagasaki Prefectures were immediately placed under a tsunami warning after the earthquake struck, with evacuation orders issued in Ishikawa, Niigata, Toyama, and Yamagata prefectures. The earthquake triggered a major tsunami warning, the first one since the 2011 Tōhoku earthquake. Tsunami waves of 5 m (16 ft) were expected, though much smaller arrived.

The evacuation orders covered 62,000 people, with 1,000 evacuees finding shelter at the Japan Air Self-Defense Force base in Wajima in Ishikawa Prefecture. The major tsunami warning was later downgraded to a tsunami warning at 20:30, about four hours after the earthquake. These tsunami warnings were later lifted at 10:01 on January 2, about 18 hours after the mainshock.

In Japan's tsunami warning system, waves anticipated to be less than 1 meter are categorized as a "tsunami advisory," those expected to reach up to 3 meters are labeled as a "tsunami warning," and waves forecasted to exceed 5 meters are classified as a "major tsunami warning."

Tsunami waves caused extensive damage in multiple coastal regions. Suzu, for example, where homes were swept away from their foundations, some even pushed further inland. The earthquake and the subsequent tsunami resulted in the destruction or damage of 90 % of the town's structures. Additionally, the tsunami overturned numerous fishing vessels, carrying some onto the shore, and flipped cars, as witnessed during a citywide aerial survey by a news helicopter. In Jōetsu, Niigata, buildings suffered damage from the tsunami, while in the Shiromaru area of Noto, Ishikawa, houses were swept away, leading to a subsequent fire.

Fire

Following the 7.5 magnitude earthquake in Wajima on Monday evening, a substantial fire broke out in the vicinity, destroying over 100 houses and shops, as reported by NHK, Japan's public broadcaster. The fire continues to blaze, and the extent of the damage is ongoing. Wajima, situated in Ishikawa prefecture, is a coastal city affected by this unfortunate incident.

Picture 2: People walk through the damaged marketplace burnt by fire after the earthquake, in Wajima, Ishikawa prefecture, Japan, on January 2. Kyodo News/AP. Source: EditionCNN

M7.5 Noto Earthquake Aftermath

As of January 18, 2024, Japan’s military dispatched dozens of soldiers to the disaster zones to join rescue efforts, with many being rescued; however, the death toll has risen to 232, with dozens injured. The earthquake displaced a total of 31,800 individuals, with approximately 27,700 seeking refuge in 336 evacuation centers solely within Ishikawa prefecture. The severity of the damage was particularly pronounced in Wajima, Suzu, and Noto, although the full extent remained uncertain.

In Wajima, a minimum of 60 houses collapsed, leaving 10 individuals trapped and over 30 people injured. Suzu also reported injuries, with approximately 5,000 houses and 90 % of structures destroyed, including many due to fires. The mayor of Suzu expressed the severity of the situation, stating that about 4,000 to 5,000 households, out of the city's 6,000, were unable to return home, emphasizing the "catastrophic" nature of the damage.

Furthermore, Japan's nuclear plant at Shika in Ishikawa province saw a rise in water level by around 3 meters since Monday's massive earthquake, operators reported. According to Hokuriku Electric Power Company, which operates the Shika power plant, the seawater level at the intake spot “was 3 m (9.8 f) higher than usual between 5.45 p.m. and 6 p.m. on Monday,” Japanese public broadcaster NHK reported.

Quantectum’s Report on M7.5 Japan Earthquake

Details of the mainshock:
- Time: 2024-01-01 at 07:10:09 UTC
              2024-01-01 at 16:10:09 Tokyo
- Location: 37.50° LAT, 137.24° LON
- Depth 10 km (6.2 mi)
- Focal mechanism: Thrust Fault
- Provider: USGS 

Picture 3: Location of the M7.5 earthquake in Japan on the 1^st of January 2024.

Quantectum tectonic stress model indicated that the tectonic shear stress in central and southern Japan increased in December 2023. At the time of the earthquake, the region was under high to very high shear stresses and the NW-SE-directed horizontal compression. The focal mechanism of the latest event is a thrust fault with NW-SE compression which is in good agreement with this model. The focal mechanism refers to the orientation of the fault plane and the direction of the fault slip during an earthquake. In this case, the observed focal mechanism matches the expectations based on the Quantectum model, suggesting a correlation between the model's forecast and the actual seismic event.

Picture 4: NW-SE-directed horizontal compression in the area of the M7.5 earthquake in Japan.

The seismic event was attributed to the local T-synchronization of seismic sequences near the western coast of Honshu, highlighted by the red color in the picture below. This phenomenon suggests a synchronization of seismic activities in that particular area. The indication is that the maximum instability of the region was anticipated to reach its peak in four days (marked by a red line on the graph below). This timeframe suggests a critical period during which heightened seismic activity or further events might occur, emphasizing the dynamic and evolving nature of tectonic processes in the region.

Picture 5: T-synchronization of seismic sequences near the western coast of Honshu.

The following graph illustrates the forecasted shear traction field (red line) and the dynamic traction field (blue line) in the epicentral region of the M7.5 earthquake in Japan. It can be concluded that the earthquake was preceded by increments in these fields due to the presence of strong tectonic waves and the established rotational singularity. Animation on this phenomenon is available on Quantectum’s X page here.

Picture 6: Shear traction field and dynamic traction field.

The seismic impact was felt widely, affecting the lives of a staggering 13 million individuals who felt the tremors caused by the earthquake. The intensity of the seismic activity was measured at a significant level VIII on the macroseismic intensity scale, which indicates severe shaking and moderate-to-heavy potential damage. Notably, in the cities of Toyama and Kanazawa, the macroseismic intensity registered at level V, reflecting a substantial and perceptible impact in those areas. In contrast, the bustling metropolis of Tokyo experienced a slightly lower macroseismic intensity, measured at level III, indicating a milder influence.

Picture 7: Macroseismic intensity map for the M7.5 earthquake near the west coast of Honshu, Japan.

Ground Effects by M7.5 Earthquake in Japan

The Geospatial Information Authority of Japan reported that certain regions in the country experienced westward displacement, with the maximum shift observed at Wajima reaching up to 1.3 m (4 ft 3 in) due to crustal deformation. At Anamizu, the land moved westward by 1 m (3 ft 3 in). However, the agency noted that these movements might be attributed to slope variations or local ground shifts. Additionally, the agency highlighted instances of crustal uplift, noting a rise of 4 m (13 ft) in western Wajima and 1.1 m (3 ft 7 in) in northern Suzu.

Conclusion

In the aftermath of the 2024 Noto Peninsula Earthquake, the devastating impact on Wajima, Suzu, and Noto unfolds, revealing widespread destruction, injuries, and a tragic loss of over 78 lives. The detailed geological insights and Quantectum's report is accessible here. As of January 3, 2024, the aftermath shows a grim picture of displaced individuals, collapsed houses, and an uncertain count of missing persons. Despite ongoing rescue efforts, the death toll has tragically risen to 64, with many more injured. Statements from local authorities, especially the mayor of Suzu, emphasize the catastrophic nature of the damage.

The recovery journey ahead is challenging, but the resilience of the affected communities, coupled with collaborative response measures, will be instrumental in rebuilding lives and communities devastated by the 2024 Noto Peninsula Earthquake.

Sources

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2) Mulia, Iyan E.; Ishibe, Takeo; Satake, Kenji; Gusman, Aditya Riadi; Murotani, Satoko. 2020. Regional probabilistic tsunami hazard assessment associated with active faults along the eastern margin of the Sea of Japan. Earth, Planets and Space. 72 (123): 123. doi:10.1186/s40623-020-01256-5. S2CID 221463717.
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6) Zhanjiu, Higa. 2024. "根こそぎ倒壊のビル、転覆した船… 能登の上空から見た甚大な被害" [Uprooted buildings, overturned ships... The extensive damage seen from above Noto] (in Japanese). The Asahi Shimbum. Accessed on 03-Jan-2023. Available at: https://www.asahi.com/articles/ASS123VWTS12UTIL00M.html.
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