Uncertainties are common in the dating of paleoearthquakes.To improve the credibility of the dating of paleoearthquakes,analysis was done on fault activity,sedimentary environment and seismo-geomorphology to investiga...Uncertainties are common in the dating of paleoearthquakes.To improve the credibility of the dating of paleoearthquakes,analysis was done on fault activity,sedimentary environment and seismo-geomorphology to investigate paleoearthquakes along the Zemuhe active fault zone.Grouped trenches were excavated near Daqingliangzi,which revealed three palaeoearthquake events aged 160a,3100a and 5500a～8900a,respectively,including recurrence intervals of about 3000a.Sedimentary processes related to strike-slip fault type earthquakes were discussed,and a sedimentary model was put forward for strike-slip faults at hillsides where drumlin and reverse scarp developed.展开更多
Based on detailed field investigations, this paper describes the geometrical characteristics and tectonic activities of the Zhangjiakou fault at the northwest of Beijing. This fault strikes mainly northwest to west, s...Based on detailed field investigations, this paper describes the geometrical characteristics and tectonic activities of the Zhangjiakou fault at the northwest of Beijing. This fault strikes mainly northwest to west, short parts of which strike near east to west, dipping north, and extends over a length of 70km. It is a major geological and geomorphologicai margin, controlling the neotectonic movement in this region. On the south side of the Zhangjiakou fault are the Late Quaternary unconsolidated deposits, forming basins; while on the other side are Mesozoic volcano debris and Pre-Mesozoic metamorphic rocks, forming lower mountains and hills. The Zhangjiakou fault consists mainly of high-angle inverse strike-slip fault and partially of normal strike-slip fault. Among these, the north-dipping NW-NWW-trending secondary faults, constituting the main fracture of the fault, have inverse characteristics; those near the EW-trending secondary faults are links of the former faults, with a smaller length and normal faulting characteristics. Thus, the Zhangjiakou fault is a north-dipping inverse and partially south-dipping normal strike-slip fault. The Zhangjiakou fault has been continuously active since the Quaternary. With the exception of the western end extension, which has been active since the late Pleistocene, the main part of the fault has been active since the Holocene. The central main segment of the Zhangjiakou fault is more active. Since the mid-late period of the late Pleistocene, the average vertical slip rate of a single fault has been over 0. 07mm/a - 0. 30mm/a. The Zhangjiakou fault has multi-slip surfaces, and the total vertical slip rate reaches 1.33mm/a, estimated from the Qingshuihe river terraces and the relevant drilling data.展开更多
基金funded by the National Key Technology R&D Program(2004CB418401)
文摘Uncertainties are common in the dating of paleoearthquakes.To improve the credibility of the dating of paleoearthquakes,analysis was done on fault activity,sedimentary environment and seismo-geomorphology to investigate paleoearthquakes along the Zemuhe active fault zone.Grouped trenches were excavated near Daqingliangzi,which revealed three palaeoearthquake events aged 160a,3100a and 5500a～8900a,respectively,including recurrence intervals of about 3000a.Sedimentary processes related to strike-slip fault type earthquakes were discussed,and a sedimentary model was put forward for strike-slip faults at hillsides where drumlin and reverse scarp developed.
基金sponsored by the Active Fault Exploration and Earthquake Risk Evaluation Program of City (Grant No. 684[2007],Hebei Provence,China)the Special Earthquake Scientific Research Program,China
文摘Based on detailed field investigations, this paper describes the geometrical characteristics and tectonic activities of the Zhangjiakou fault at the northwest of Beijing. This fault strikes mainly northwest to west, short parts of which strike near east to west, dipping north, and extends over a length of 70km. It is a major geological and geomorphologicai margin, controlling the neotectonic movement in this region. On the south side of the Zhangjiakou fault are the Late Quaternary unconsolidated deposits, forming basins; while on the other side are Mesozoic volcano debris and Pre-Mesozoic metamorphic rocks, forming lower mountains and hills. The Zhangjiakou fault consists mainly of high-angle inverse strike-slip fault and partially of normal strike-slip fault. Among these, the north-dipping NW-NWW-trending secondary faults, constituting the main fracture of the fault, have inverse characteristics; those near the EW-trending secondary faults are links of the former faults, with a smaller length and normal faulting characteristics. Thus, the Zhangjiakou fault is a north-dipping inverse and partially south-dipping normal strike-slip fault. The Zhangjiakou fault has been continuously active since the Quaternary. With the exception of the western end extension, which has been active since the late Pleistocene, the main part of the fault has been active since the Holocene. The central main segment of the Zhangjiakou fault is more active. Since the mid-late period of the late Pleistocene, the average vertical slip rate of a single fault has been over 0. 07mm/a - 0. 30mm/a. The Zhangjiakou fault has multi-slip surfaces, and the total vertical slip rate reaches 1.33mm/a, estimated from the Qingshuihe river terraces and the relevant drilling data.
