Slip-rates And Segmentation Feature Of Surface Ruptures Caused By Earthquakes Along The Altyn Tagh Fault Zone Since Late Quaternary

The Tibetan Plateau is the most mysterious highland on continents in the world. Its average elevation reaches 4000m and it attracts numerous explorers and scientists. The process of formation and evolution of the Tibet Plateau influence the tectonic patterns and climate of China continent greatly. The Altyn Tagh fault Zone, as the northern boundary of the Tibetan Plateau, winds more than 1500km from Lazhulong in Tibet province to Kuantanshan in Gansu province. Its linear character is conspicuous on satellite images and topographic maps with a strike of N75癊. In recent years, accompanying further studies on the Tibetan Plateau, the Altyn Tagh fault zone becomes a pop topic of geoscientific research. Ten years ago, China Seismological Bureau organized a group who worked on the Altyn Tagh fault, finished a detailed study on the large fault and compiled a book named " The Active Altyn Tagh Fault Zone". Even by now, this work is one of the most systematic works on active tectonics on the fault. Meanwhile, scientists from other countries are working on the fault zone diligently. As the northern boundary of the Tibetan Plateau, the Altyn Tagh fault separates two tectonic units: the Tarim basin and the Tibetan Plateau. The geomorphology features north to the fault and south to the fault are totally different and the elevation difference reaches 3000m. To study such a long fault zone is of great importance to know the formation and evolution of the Tibetan Plateau and its contribution to the uplift of the Tibetan Plateau and underthrusting of the India Plate.This thesis is focused on slip-rates of the Altyn Tagh fault and the segmentation features on its eastern part. The specific items are:1, the surface rupture segmentation on the eastern part of the Altyn Tagh fault and its seismological features,2, the sinistral slip-rate of the whole Altyn Tagh fault,3, the contribution of strike-slip on the Altyn Tagh fault in assimilating the underthrusting of India Plate beneath Euro-Asia Plate,4, the relationship between strike-slip on the Altyn Tagh fault and vertical and horizontal movement of the Northern Qilianshan thrust.With the progress of technology, new methods come forth continuously and furnish new ways for scientific research. In the last century, tremendous progresses in chronology, remote-sensing, computer and astronomy allow us to study geology with new methods. With satellite images and aerial photos we can observe any place on the Earth without stepping out our office. With help of fast computers, numerous satellite images can be analyzed in short time. All of these technologies improve our efficiency of working greatly.During the process of research, the following methods were adapted.First, by analyzing the TM and Spot images on the fault in detail, the surface ruptures of the fault and geometrical relationship between different parts of the Altyn Tagh fault are found. After that, mapping the terraces of rivers across the fault and alluvial fans near the fault, by this, offset features of different geological bodies near the fault and segmentation of the fault are analyzed. Then the sites, where chronological samples for dating are gathered, are determined.Secondly, by field investigating, chronological samples are collected and the indoor analysis results are corrected. By dating the samples collected in the fieldwork, ages of offset terraces or alluvial fans are obtained. According to offset features and ages of the terraces and fans, segmentation the fault is determined and its strike-slip rate is calculated.Because of drought climate and scarcity of plant in the study region, it is hard to find carbons in the region. Regarding the condition of chronology laboratory in our institute and the possible ages of the samples, thermo-luminescent dating method is adapted.To calculate the strike-slip rate on a fault, two variables are indispensable. One is displacement and the other is the age of the displacement. To get the slip-rate accurately, only offset of terraces and alluvial fans is u...