Earthquake epicentral distribution - seismic focal depth

In China, shallow, middle and deep earthquakes are distributed, but the vast majority (99%) of the earthquakes belong to shallow crustal earthquakes.

Middle-source earthquakes occur mainly in two regions. One is the western boundary of the Pamir area, the focal depth of the range of 100-160km; the other is the island of northeast and southeast of the sea, the focal depth of the maximum depth of 270km. The former is the edge of the Hindu Kush source seismic zone, which is part of the Pacific island arc seismic belt. The deep earthquakes are only distributed in Yanbian, Hunchun and Heilongjiang provinces of MuLing and Mudanjiang, and the focal depth is 400-600 km. The earthquake here is due to the Western Pacific Japan arc groove Benioff caused by the band inserted into the mainland of China.

The shallow earthquakes, which are widely distributed in the mainland of China, are generally in the range of 0-30 km in the crust, and more than 90% of the strong earthquakes above magnitude 6 occur in the depth range of 10-25 km. In addition, due to the different crustal structure, the distribution of these shallow earthquakes in different places are also slightly different.

Taiwan earthquake is an island arc seismic belt, the earthquake occurred and plate subduction, so shallow source earthquakes are distributed from 0-70km, they are only located in latitude 23 ° -24.2 ° range.

In the eastern part of China, the crustal thickness of the South China Earthquake is 28 ~ 40km, the focal depth of the earthquake is the shallowest, generally in the range of 5-20km. The crustal thickness of the North China Earthquake is 30-45 km, and the seismic focal depth ranges from 5 to 30 km. The depth of shallow earthquakes in the northeastern seismic zone is less than 20km, the crustal thickness in the Sichuan-Yunnan earthquake area is 40-55km, and the depth of the shallow earthquakes is in the depth range of 5-40km.

The crustal thickness of the seismic zones in western China and Qinghai-Tibet Plateau ranges from 50 to 70 km, and their focal depths are gradually reduced from south to north. The depth of the shallow earthquakes ranges from 10 to 70 km. In the southern part of the plateau, the focal depth is 15-70 km, the central part is 10-40 km, and the northern part is 10-30 km.

The crustal thickness of the seismic zone in Xinjiang is 45-60 km. The source of the western Tianshan seismic belt is deeper, 10-50 km, and the eastern part is 10-30 km.

Source: Atlas of China's Natural Disaster System