Exploration On Active Faults And Establishment Of Quaternary Key Sequences In Changchun City

Changchun City active fault exploration and seismic risk assessment project is one of the major scientific project (2004-1138) that Cities active fault exploration and seismic risk assessment of sub-project. The core of this work is resolve the item of city's fracture, fractured latest activities, fractured deep background, risk in earthquakes of fracture, ground fault danger and disaster reduction measures.The active fault is a modern structure, which is closely related to earthquakes and geological disasters, directly threat to the security of the city and project safety. Development of all active faults in urban areas, including the lie concealed active fault which is known as the drop-off fracture. It would control the way down a city-devastating earthquake damage, which should caused heavy casualties. Earthquake fracture cause the fault surface which is the most serious fault with the displacement and destruction that modern technology is still unable to resist. This phenomenon attracted great attention from Chinese and foreign scientists, and also attracted great attention from all governments.With rapid economic development, the construction of large cities and urban centers growing scale are rapid growth in population density. In this situation, how to make people more secure in living environment, has become an issue of great concern in today's society. The city's geological and seismic activities as one of the major risk factors. Seismic and geological activity is the direct cause of the active fault, it has great significant that active fault exploration and seismicrisk assessment project in many cities. The facts have proved that the building structures of the city or town, can be effectively avoided active faults, also decide the city or buildings can be effectively avoided the earthquake disaster.Changchun, located in the integration of the mountains and plains,the side of Zhang guang cai Range and Song liao Basin basining , the eastern of the southeast apophysis of Song liao Basin. East North - the work area NNE fault rupture backbone, but also to the development of a West-North and South–North fault to rupture. The East–North is the main fault rupture Yi tong– Shu lan (1),Song liao Basin eastern margin fracture (2);The West-North fault is the second Song hua River fault (3), Ying di zi– Fan jia tun fracture (4),East Liao River fracture (5);a north-south fault rupture is Yi tong River fracture(6).East-North and West-North fault rupture crossed each other to form a tectonic earthquake construct, become strong earthquake belts. Su lan-Yi tong rupture occurred the northern Jilin 5.0 magnitude earthquake in June 1937, the eastern margin of Song liao Basin occurred Chang chun yu shu 5.8 magnitude earthquake in April 1960, Changchun Fan jia tun 5.2 earthquake occurred in October 1966.In addition, the sudden and devastating earthquake disaster brought great psychological pressure and infection of the efficiency and impact on social stability and economic development.Summing up the above, we can see that the study of active faults in Changchun areas and active fault map will be of advantage to scientific significance,also to the social and economic.The circum-Pacific seismic belt of northeast, in theory should be the earthquake-prone zone. Therefore, we should be fully aware of the basic geology, specially the study of activities are closely related to the seismic fracture for the survival for humanity and social development. Changchun geological and construct evolution of the long form to the east-north of the construct system, which has entered a new period of construct movements, occurred in the Tertiary-Quaternary period of the Himalayan movement. Mesozoic strata regional uplift and erosion accepted, formed from the southeastern to westnorthern region in favor of the topography. Since most of the tertiary period to uplift, the Quaternary Pleistocene began sinking. As Quaternary loose sedimentary cover serious rock outcrop small faults were not very evident. This is the fault of the area of research and prediction of seismic activity caused certain difficulties. Therefore, multidisciplinary and comprehensive study of the comprehensive use of various techniques for the Changchun and its surrounding areas, the new round of active faults investigations have important practical significance.Objective of this article is to study the different terrain in the target zone, controlled Quaternary geology unit within the borehole, analysis of the core drilling stratigraphic sections, the system's formation and testing of the samples collected, analyzed and compared borehole profile section Quaternary strata. According to two bored standards stratigraphic sequence, sedimentary characteristics, age, pollen analysis and field survey, the establishment of the Quaternary standard section, as a next step the basis of active fault exploration.The course of the study in this article exploration and controlled through the establishment of Quaternary research section the main line to the key issues. The Quaternary sediments to study the causes and times for breakthrough research, focus on the activities fracture geometry and kinematics. Discovery and discriminate of ancient earthquake, Multidisciplinary integration of the integrated use of the method means Quaternary geology and seismic geologic studies.In a comprehensive analysis of various information based on the basis of remote sensing data distribution issues with the goal of the plane fault, seismic geological surveys conducted field. Completion of the inspection point 45 field geological and structure, fault line or across a fault recourse through the 25 km long route, The Quaternary sediments observed section 18, completed the Quaternary sediment sample thermoluminescence age 27, 14C dating samples3. Geophysical work in the case has not yet been completed, in order to expose the fault launched a sound frequency electric field measured the earth, completed a total of 25 lines, 826 points physical measurements, the total length of 8260m lines. Excavation of trenches eight, complete earthwork 470 m3 .After drilling exploration, compilation, sample tests, and field investigations Quaternary geological survey and laboratory tests analysis establishment of the Mid- Pleistocene to Late-Pleistocene loess deposit, Late Pleistocene diluvial material and the Late Pleistocene - Holocene alluvial material for the standard sections.The Mid-Pleistocene to Late-Pleistocene loess deposit mainly in the second floor of corrugated, the largest thickness 30m above, lithology mainly clay or silty clay. In some areas, which lack Middle Pleistocene loess accumulation and the Late Pleistocene loess deposit directly above coverage in the Cretaceous.Distribution of Late Pleistocene diluvial material limited, only a few larger gully along or in gullies Formations, with stratification, but sorting and frictional extent of grains are relatively poor, belonging to the causes diluvial material. This accumulation and Yi tong River sediment level terraces belonging to the same period in heterogeneous product.Late Pleistocene - Holocene alluvial distributed Yi tong River and other major rivers in the level terraces. Late Pleistocene alluvial deposits with the dual structure in evidence, sedimentary rhythm clearly, obvious local sedimentary section. Late Pleistocene alluvial terraces constitutes a level below, and directly covered by Holocene alluvial or black soil. Holocene alluvial distributed Yi tong River or other major rivers in the upper level terraces, fully with the organic-rich dark gray dye mainly sandy clay. Some of the higher terraces in river valley on both sides, formed black soil in this period.