| 按大地构造观点进行中国地震地质区划的尝试 |
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| AN ATTEMPT TO THE SEISMOGEOLOGICAL REGIONALIZATION OF CHINA ACCORDING TO THE TECTONIC POINT OF VIEW |
| The territory of China can be subdivided into the following seismogeologcal regions andzones.
Marginal Pacific Seismic Domain (Seismic Domain of Eastern China):
Inner Domain: Strong Seismic Region of Taiwan; Deep Seismic Region of Yenji and Mulin
Outer Domain: (Intraplate Seismic Domain) Northern, Weak Seismic Region; Central, Strong Seismic Region (Sino-Korean Paraplatform); Southern, Weak Seismic Region.
North-South Seismic Zone:Interference zone between Eastern and Western Seismic Domain. Tethys-Himalayan Seismic Domain (Seismic Domian of Western China): Inner Domain, Chiefly Himalayan Seismic Zone; Outer Domian (Intraplate Seismic Domian); Northern, Strong Seismic Region; Central, Weak Seismic Region (Tarim Platform); Southern, Strong Seismic Region.
The Strong Sesismio Gegion of the Sino-Korem Paraplatform is further subdividea into:(1)Tranquil Zone of the Ordos; (2)Western, Strong Seismic zone; (3)Weak Seismic Zone of the Taihangshan Uplift; (4)Central, Strong Seismic Zone; (5)Eastern, Strong Seismic Zone; (6)Intermediate Seismic Zone of Jiaoliao; (7)Strong Seismic Zone of the Northern Marginal Fault of the Huaiyang Massif; (8)Weak Seismic Zone of the Nei Monggol (Inner Mongolian) Axis.
China is dominated by three stess fields. The Pla-Asiatic stress field in the north is no more active since Cenozoic time. The Marginal Pacific stress field, corresponding to the Marginal Pacific Seismic Domian, is induced by the westward drift of the Pacific Plates. The Tethys-Himalayan stress field, corresponding to the Tethys-Himalayan seismic Domian, is induced by the northward drift of the Indian Plate.
The Sino-Korean Paraplatform, being composed of granitic rocks, is a rigid body and is characterized by generally NE-SW or NNE-SSW directed deep fault zones, which, when acted upon by E-W compression coming from the Pacific Plate, will cause sudden displacement with dextral shear movements resulting in strong earthquakes. The Northern and Southern, Weak Seismic Regious, being composed of non-grantic rocks, "yield" easily under compression so that strong earthquake seldom occur.
Like Ordors, the Tarim Platform is a rigid massif, and is accordingly devoid of strong earthquekes. On the other hand, the Tibetan Plateau, being acted upon at right angles by the strong compression from the Indian Plate, is characterized by many strong earthquakes and this northward drive causes the Tarim Platform to transfer the stress to the Tienshan, resulting in strong earthquakes in the latter region.
The North-South Seismic Zone, being acted upon by stress both from the Indian Plate and the Pacific Plate, is domianed by strong earthquakes and is therefore considered as the interference zone of the two stress fields.
Tapponier is of the opinion that the earthquake of the Sino-Korean Paraplatform are directly connected with the drifting of the Indian Plate. The author thinks this is unlikely. Sino the Cenozoic tectonic history of the Sino-Korean Paraplatform forms a part of the hist eory of the Marginal Pacific Tectonic Domian, the author prefers to consider the seismicity of the Paraplatform as belonging to the Marginal Pacific Seismic Domian.
Serveral rules govern the production of strong earthquakes.(1)The majority of strong earthquakes occur on deep faults, esp. at the intersection areas of two systems of these faults. (2)In the case of parallel fault zone, when the eastern zone, acted upon by western stress, bursts into strong earthquakes, the western zone often shows weak earthquakes, and vice versa. This means that the western zone is pretected by the eastern zone, in other words, the eastern zone acts as a screen. We call this phenomenon the screen effect. (3)Depressions, esp. Cenozoic depression, often coincide with strong seismic zones while uplifts are characterized by waek earthquakes. (4)Migration of seismic epiceuters often occurs both transversely and longitudinally with regard to the faults. Along a deep fault zone strong earthquakes are localized in resistant sections while smooth sections are free from them. |
| HUANG Ji-qing.1979.AN ATTEMPT TO THE SEISMOGEOLOGICAL REGIONALIZATION OF CHINA ACCORDING TO THE TECTONIC POINT OF VIEW[J].Acta Geoscientica Sinica,1(1):18-31. |
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