M5.9 Earthquake in Gansu Province – China’s 9th Devastating Earthquake

M5.9 Earthquake in Gansu Province Basic Information 

On the 18th of December 2023, at 23:59 local time, a 5.9 magnitude earthquake struck the northwestern province of Gansu, China. The disaster resulted in the loss of at least 135 lives, with over 980 people injured. Additionally, many houses and buildings were damaged or completely destroyed. Media reports indicate that the tremor disrupted power and communication lines. The resulting damage and fatalities have marked it as the 9th most devastating earthquake in China's history. 

Details of the earthquake are as follows: 
- Time: 2023-12-18 at 15:59:30 UTC
 ​  ​ ​ ​ ​ ​ ​ ​ ​ ​ 2023-12-18 at 23:59:30 Shanghai 
- Location: 35.74° LAT, 102.83° LON
- Magnitude: Mww5.9 
- Depth: 10 km (6.2 mi) 
- Provider: U.S. Geological Survey (USGS) 

Picture 1: Location of the magnitude 5.9 earthquake in Gansu province, China, on the 18th of December 2023.

M5.9 Earthquake in Gansu Province Damage and Response 

As of the 21st of December 2023, Thursday, authorities have confirmed 135 fatalities. Within Gansu province, 113 individuals were discovered deceased, and 784 were injured. Meanwhile, the death toll in the neighboring Qinghai province reached 18, with 198 reported injuries. 

Chinese media reported that 78 people were found alive in Gansu province, where rescue operations ended on Tuesday afternoon leading to a shift in focus towards the treatment of the wounded and the resettlement of residents in anticipation of the looming months-long winter. 

Besides causing injuries and fatalities, earthquakes also damaged roads, power and water lines as well as agricultural production facilities. In addition, it also triggered land and mudslides. 

Within 50 km (31 mi) of the epicenter on the side of Qinghai province, the earthquake affected 22 towns and villages, out of that, two villages suffered the worst damage. In Gansu province, more than 207,000 homes were damaged and nearly 15,000 houses collapsed, affecting more than 145,000 people. To help the survivors, more than 128,000 emergency supply items including tents, quilts, and folding beds, were delivered, while some basic food such as steamed buns and instant noodles were provided to the victims. 

The prompt and effective emergency response initiated by the National Development and Reform Commission, along with other departments, commenced shortly after the earthquake and continues to the present. Rescuers face persistent challenges in the high-altitude and remote complex terrain. Despite the earthquake striking a relatively remote region, it remains densely populated. 

Braving below-freezing conditions, rescuers continue the search for survivors and victims, while survivors face months of uncertainty ahead without permanent shelter. Temperatures around the quake epicenter in Gansu province fell to about minus 15 degrees Celsius on Tuesday night. 

Picture 2: Rescuers searching for survivors after the magnitude 5.9 earthquake in Gansu province, China. Credits: Chinese social media Douyin users.

Furthermore, the Organization Department of the Communist Party of China (CPC) Central Committee allocated 100 million yuan (approximately $14.09 million) from CPC membership fees to support disaster relief initiatives in the earthquake-affected provinces of Gansu and Qinghai provinces. 

These funds are specifically designated for primary-level Party members, officials, and individuals actively engaged in disaster relief efforts, as well as Party members and civilians who have faced adversity in the aftermath of the earthquake. Additionally, the allocated dues will be utilized to restore educational facilities for primary-level Party members who suffered damage during the seismic event, as outlined by the department. 

The department emphasized the need for primary-level Party organizations and members situated in the quake-affected regions to serve as exemplars. Their responsibilities include safeguarding the lives and property of the populace with unwavering dedication, effectively executing disaster relief tasks, and contributing diligently to post-disaster reconstruction efforts. 

Quantectum’s Report on M5.9 Earthquake in Gansu Province 

At Quantectum, we run the most advanced Physical Earthquake Forecasting Models of global time-dependent tectonic stresses, local tectonic instabilities of faults and fault zones, critical regions, and tectonic tractions. Based on them, we create earthquake forecasts and past earthquake reports.  

The magnitude 5.9 earthquake in the Gansu province reached level VIII macroseismic intensity, which was associated with violent shaking and could seriously damage the area's buildings and infrastructure, according to Quantectum’s ground motion modeling results. The macroseismic intensity map below also lists potentially exposed cities. The most potentially exposed cities were Linxia Chengguanzhen (pop. 274,000), Qu’ao (pop. 3,000), Madang (pop. 6,000), Wangge’ertang (pop. 4,000), and Damai (pop. 4,000). 

Picture 3: Macroseismic intensity map for the magnitude 5.9 earthquake in Gansu province, China.

The image below displays one of the corresponding tectonic waves that enhanced tectonic tractions and led to multiple earthquakes along it, including the magnitude 5.9 earthquake in Gansu province in China. Tectonic waves travel through or over the Earth and are usually generated by relative movements of the Earth's tectonic plates (earthquakes). In other words, tectonic waves are formed by slow deformations in the Earth’s crust. When traveling through regions characterized by high shear traction their interaction can cause earthquakes. Read more about the advanced modeling of tectonic waves and their utilization in Quantectum’s earthquake forecasting here. 

Picture 4: Tectonic waves that triggered the magnitude 5.9 earthquake in Gansu province, China.

The earthquake, depicted as the black column on the tectonic traction chart below, occurred during a notable increase in the shear traction field, marked by the red line, and the rise of the dynamic traction field, marked by the blue line. These variations in traction were linked to the activity of multiple active tectonic waves passing through the region. 

 
Picture 5: Chart of shear stress field and dynamic traction field for the magnitude 5.9 earthquake in Gansu province, China. 

The constant dynamics of tectonic activity, characterized by the continual movement and interaction of Earth's crustal plates, contributed to the progressive accumulation of stress along fault lines in Gansu province. As these stress levels intensified, they eventually reached a critical threshold, triggering the release of energy in the form of seismic waves, culminating in the observed magnitude 5.9 earthquake. The region of the earthquake has been also characterized by high normalized shear stress with an approximately N-S-directed maximum horizontal compression. 

Shear stress is a force that acts parallel to the Earth’s surface, causing one layer to slide over an adjacent layer. Normalized shear stress refers to the measurement of this force in relation to the area over which it is applied. In addition, maximum horizontal compression denotes the direction in which the strongest compressive forces are acting horizontally. In this context, the maximum horizontal compression is directed approximately north to south. This alignment implies that the geological forces causing compression are primarily exerted in this specific orientation.

Picture 6: Shear stress map in the area of magnitude 5.9 earthquake in Gansu province, China.

Earthquake Forecast for China 

Especially in the western part of the country, we can observe increases in the shear traction values by the end of the year 2023. Our UHD models indicate that regional fault systems in Xinjiang-Xizang, southern Xinjiang, and Xizang-Qinghai will be strongly unstable due to intense chaotic synchronizations along them. The image below shows regions where the critical earthquake-triggering potential will have a maximum during the rest of the year 2023. The graph shows the probability of earthquake triggering in different magnitude levels, calculated based on the shear traction – and critical instability alarm field. 

Picture 7: Critical earthquake-triggering potential in China by the end of the year 2023. 

Conclusion 

Following the magnitude 5.9 earthquake that struck Gansu province on December 18, 2023, the aftermath has been severe, resulting in profound consequences for the landscape and communities of the region. 

Its destructive aftermath and the loss of lives elevated it to the rank of the 9th most devastating earthquake in Chinese history. As the impacted communities deal with the consequences, there is an imperative need to not only prioritize immediate relief efforts but also contemplate enduring strategies for resilience and preparedness. 

To learn more about the seismicity in China, you can read our blog about it here. 

Sources: 
1) Diviggiano, Alessandro, Yin, Xiaoyu, and Lee, Liz. 2023. Chinese earthquake victims pulled to safety in subfreezing weather, 132 confirmed dead. Accessed on 20-Dec-2023. Available at: https://www.independent.ie/world-news/asia-pacific/chinese-earthquake-victims-pulled-to-safety-in-subfreezing-weather-132-confirmed-dead/a922852715.html 
2) Xinhua. 2023. CPC Organization Department allocates 100 mln yuan to aid quake-hit regions. Accessed on 20-Dec-2023. Available at: https://english.news.cn/20231220/94f559d5a7f84e9c87a52a0e4b14d6b8/c.html