A Study On The Characteristics Of Recent Tectonic Deformation And Earthquake Activity In North China

Block motion is one of the most remarkable features of present tectonic deformation in the Chinese mainland. The active block theory has been formed as the more and more scientists are convinced of universality of block activities by studies. The active blocks are geological elements with similar motion modes, which were formed in Late Cenozoic and cut and enclosed by strong active tectonic belts from Late Quaternary to present-day. Deformation and major earthquakes usually occur along their boundaries. The active blocks have four basic characteristics: newly generating, layering and ordering, entirety and solid. The Chinese mainland and its adjacent regions could be divided into six active tectonic block regions(the first order): Tibet, West Region, North China, South China, Northeast China and China-Burma region. The North China active tectonic block region is located at East Chinese mainland and borders to Tibet, West region, South China and Northeast China active tectonic block regions. Its earthquake activity and tectonic deformation are the strongest in eastern China, and it is one of regions in the Chinese mainland with high seismicity. There are dense population and highly developed economy in North China. The capital of China is also located, in the North China. It is important for earthquake prevention and disaster reduction to study tectonic deformation and seismicity regularity of this region. This thesis is focused on detailed studying recent tectonic deformation and earthquake activity of North China. The purpose is to reveal the relationship of tectonic deformation and earthquake activity between active tectonic block and their boundaries. The author has also studied the mechanism of tectonic deformation and strong earthquake activity in North China.1 The active tectonic blocks and strong earthquake activity in the Chinese mainlandBy studying the relationship between active blocks and strong earthquake activity in the Chinese mainland, the author further confirms that strong earthquakes are obviously controlled by active blocks. More than 52% earthquakes(M>6.0), more than 73% earthquakes(M>7.0) and 100% earthquakes(M>8.0) occur along boundaries belonging to the first and second order blocks. Major earthquakes often occur in the belts where several active blocks interact. Especially there are more and denser strong earthquakes in the belts where several active tectonic block regions interact. The activity of active blocks is different at varied tectonic positions. The activity of western active blocks is obvious stronger than that of the eastern active blocks with the South-North Earthquake Belt as a boundary. The activity of Tibetan active tectonic block region is strongest in the west part of the Chinese mainland, and the activity of North China active tectonic block region is strongest among eastern active tectonic block regions2 The North China active tectonic block region and its strong earthquake activityAfter studying tectonic evolution characteristics of the North China active tectonic block region based on previous research, author has postulated that the main tectonic elements have rejuvenilezed. Some boundaries followed the old tectonic belts, and some boundaries were newly formed during geological evolution history. By geology, geophysics, strong earthquake activity data and so on, the North China active tectonic block region could be divided into three active tectonic blocks(Ordos, North China Plain and East Shandong-Yellow Sea active tectonic blocks)as second order active tectonic block. Some active tectonic blocks could be divided into lower order active tectonic blocks further(sub-block, min-block).By studying strong earthquake activity within the North China active tectonic block region, it is confirmed that active tectonic blocks control strong earthquake distribution. Between boundaries andblock interiors, the differences of the density of earthquakes(M>5.0) are more than 2.5 times, and that of the energy released in per square kilometers exceed 30 times. The 7 great ear...