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Shan Xinjian and others of our Institute Visited Taiwan

2015/12/29 9:44:59

From June 15, 2015 to June 21, 2015, researchers Shan Xinjian, Liu Yunhua and Wen Shaoyan of the Institute of Geology, CEA went to Taiwan for cooperative exchange at the invitation of Prof. Hu Zhiqing at the Department of Geosciences, National Taiwan University. Their purpose was to learn the achievements and advantages of Taiwan in research on deformation observations of active tectonics, numerical simulation of earthquakes and dynamic inversion of seismic source, and strengthen cross-straits exchange and cooperation in geosciences. This visit would also promote the implementation of the project “Research on deformation characteristics and mechanism of the Altun-Haiyuan Fault Zone on the northern margin of the Tibetan Plateau” - a key project for cooperative research of Chinese Mainland and Taiwan supported by NSFC. As the visit coincided temporally with the 8th World Chinese Geological Congress in Taiwan. researchers Qu Chunyan, Song Xiaogang and Zhang Guohong of the project team, who attended this meeting, also joined the visit on June 16 after the end of the Congress.

Figure 1. Visiting Department of Geosciences, National Taiwan University and exchanging ideas in cross-straits cooperation project

Prof. Hu Zhiqing introduced the organizational structure, research framework, projects and human resource of the department. The two sides exchanged ideas in details on how to carry out cooperation in the Altun-Haiyuan fault zone, expressed respective opinions on research areas, erection of observation instruments, cooperation, work division and research plan, and formulated a detailed plan. After the exchange of project cooperation, under the leadership of Prof. Hu Zhiqing, the visitors conducted a field observation to the surface rupture zone of the Chi-Chi earthquake, the Tainan mud volcano and the Chishang fault.

Figure 2. Left: Bridge rebuilt after being dislocated by 1999 Chi-Chi earthquake   Right: Shihkangpa Reservoir dislocated in the 1999 Chi-Chi earthquake

The surface rupture zone of the 1999 Chi-Chi earthquake is about 100 km in total. By fault features, it is divided into four sections from south to north: Chushan section, Tsaotun section, Shihkang section and Cholan section. Each section is about 25km long. The representative Shihkang section was selected as the study point. This section was formed in the rock strata on the hanging wall of the Chelongpu fault. In view of the outcrop of the earthquake fault, the areas to the south of Shihkangpa are all of sinistral thrust with certain continuity. The photos in Figure 2 show that the area is close to Fongyuan, the fault turning point. The photos were taken with the lens facing north. This bridge was destroyed by the earthquake and later was restored. As the two fault walls have a large fall, the deck is no longer horizontal. Instead, it is concave in the middle. After passing the bridge, you can see Shihkangpa Reservoir not far from the bridge to its east. This reservoir crosses the two walls of the fault. During the earthquake, the dam body was dislocated and the hanging wall was lifted, resulting in 10m of dislocation of the two fault walls.

The study group moved along the first line of the Qishan fault, and arrived at Yanchao Town and investigated a famous mud volcano in Taiwan: Wushanding volcano. It is the highest mud volcano, about 3.5m high, with a gradient of about 50 degrees. It is a standard mud cone. It erupts once every a few seconds. The erupted slurry is very thick and a mud bubble with a diameter of about 50cm is formed. The Qishan fault now shows obvious activity, resulting in bending of the tunnel near the fault (Figure 3, 4).

In the end, the study group also visited the Chishang Fault generated from squeeze between the Eurasian and Philippine plates. The study group went to the Dapo Primary School on the fault zone (Figure 5). The photo shows that a playground slide has been lifted, and on the right of the slide, there is a creep tester – an instrument monitoring displacement. Here is a section of the Chishang fault with the most obvious creep, with a slip rate about 2~3cm per year. It is very clear that the civil buildings and other buildings along the Chishang fault are destroyed due to the fault creep.

Figure 3. The tunnel passing through Chishang fault was bent due to fault activity

Figure 4. Mud cone of the mud volcano (left) and mud bubble formed in the cone (right)

Figure 5. Observation point at Chishang fault on the playground of Dapo Primary School

Through attending World Chinese Geological Congress, exchange visit to National Taiwan University and field observation on Taiwan Island, the study group to Taiwan had learned more on the research trends, advantaged fields and talent cultivation methods of Taiwan region in the geoscience, further clarified the way and prospect of bilateral cooperation, and deepened understanding on tectonic evolution and arc-continent collision of Taiwan Island.