Based on the horizontal movement velocities and their error estimations of 144 GPS stations in North China de-duced from the results obtained from multiple GPS measurements carried out in the period of 1992~2001, the ...Based on the horizontal movement velocities and their error estimations of 144 GPS stations in North China de-duced from the results obtained from multiple GPS measurements carried out in the period of 1992~2001, the horizontal deformation in the area is studied. The movements, entire deformations, local deformations, activity patterns and intensities along the boundary zones are derived. And then the risk of strong earthquake in the area is estimated. In the research, the horizontal displacement observations can be considered as the sum of three parts. The first part is the entire motion following Eurasian plate, which can be derived from NUVAL-IA model; the second part is the relative motions and deformations between the sub-tectonic blocks in the studied area, which can be derived from a set of displacement observations determined by the expanded QUAD method in the paper; the third part is the local deformations and errors in the sub-tectonic blocks, which can be described as the inhomoge-neous strains of the block. The method and results are introduced in detail in the paper.展开更多
The tendency and dynamic characteristics of horizontal movement along the Shanxi fault zone have been analyzed using the data obtained from 6 repeated measurements (1996～2001) in the GPS monitoring network arranged a...The tendency and dynamic characteristics of horizontal movement along the Shanxi fault zone have been analyzed using the data obtained from 6 repeated measurements (1996～2001) in the GPS monitoring network arranged along the Shanxi fault zone. The results indicate: (1) the tendentious activity of the present stage is characterized by a W trending movement along the northern segment of the zone, an E trending movement along the southern segment and counter clockwise differential activity on the whole, but the intensity of the tendentious activity is not high. The tendentious differential movement is only about 3 mm/a in the direction perpendicular to the fault zone from the south to the north, and its stretch in the SN direction is only 1 mm/a and mainly occurs along the north segment of the fault; (2) The azimuth of the principal compressive stress field reflected by the tendentious movement is 72°; (3) The property of annual activity is not the same, even contrary to one another or deviates from the tendentious activity. Therefore, the parameters of the strain field derived from them dont reflect the physical characteristics of the basic stress field. (4) The high frequency movement (yearly) does not only exist but is also complicated by an intensity several times higher than that of the tendentious movement; (5) Obvious differential movements, including strike slip, can not be seen in either in secular activity or annual activity on both sides of any fault. The tendentious movement not only verifies the conjecture of “strong in the south and weak in north”, which is the basic feature forcing the western boundary of the North China area, but it also extends to the hinterland of North China. The fact that there is no obvious differential activity on both sides of the fault might indicate that the differential activity among the intraplate blocks is completed by gradual variation in a certain space, rather than the abrupt change bordered by a fault or narrow stripe zone. The obvious dynamic activity might indicate: (1) there is stress disturbance in the basic stress field; (2) the inhomogeneous or non synchronous variation that appeared in the regional stress and strain fields was due to the different physical property of the medium; (3)the response occurred because of a variety of external variations. The movement in 2001 shows that the Daixian county and its adjacent area might be the boundary segment for the relative differential activity. More attention should be paid here.展开更多
基金State Key Basic Research Development and Programming Project Mechanism and Prediction of Strong Continental Earthquakes (G1998040703).
文摘Based on the horizontal movement velocities and their error estimations of 144 GPS stations in North China de-duced from the results obtained from multiple GPS measurements carried out in the period of 1992~2001, the horizontal deformation in the area is studied. The movements, entire deformations, local deformations, activity patterns and intensities along the boundary zones are derived. And then the risk of strong earthquake in the area is estimated. In the research, the horizontal displacement observations can be considered as the sum of three parts. The first part is the entire motion following Eurasian plate, which can be derived from NUVAL-IA model; the second part is the relative motions and deformations between the sub-tectonic blocks in the studied area, which can be derived from a set of displacement observations determined by the expanded QUAD method in the paper; the third part is the local deformations and errors in the sub-tectonic blocks, which can be described as the inhomoge-neous strains of the block. The method and results are introduced in detail in the paper.
文摘The tendency and dynamic characteristics of horizontal movement along the Shanxi fault zone have been analyzed using the data obtained from 6 repeated measurements (1996～2001) in the GPS monitoring network arranged along the Shanxi fault zone. The results indicate: (1) the tendentious activity of the present stage is characterized by a W trending movement along the northern segment of the zone, an E trending movement along the southern segment and counter clockwise differential activity on the whole, but the intensity of the tendentious activity is not high. The tendentious differential movement is only about 3 mm/a in the direction perpendicular to the fault zone from the south to the north, and its stretch in the SN direction is only 1 mm/a and mainly occurs along the north segment of the fault; (2) The azimuth of the principal compressive stress field reflected by the tendentious movement is 72°; (3) The property of annual activity is not the same, even contrary to one another or deviates from the tendentious activity. Therefore, the parameters of the strain field derived from them dont reflect the physical characteristics of the basic stress field. (4) The high frequency movement (yearly) does not only exist but is also complicated by an intensity several times higher than that of the tendentious movement; (5) Obvious differential movements, including strike slip, can not be seen in either in secular activity or annual activity on both sides of any fault. The tendentious movement not only verifies the conjecture of “strong in the south and weak in north”, which is the basic feature forcing the western boundary of the North China area, but it also extends to the hinterland of North China. The fact that there is no obvious differential activity on both sides of the fault might indicate that the differential activity among the intraplate blocks is completed by gradual variation in a certain space, rather than the abrupt change bordered by a fault or narrow stripe zone. The obvious dynamic activity might indicate: (1) there is stress disturbance in the basic stress field; (2) the inhomogeneous or non synchronous variation that appeared in the regional stress and strain fields was due to the different physical property of the medium; (3)the response occurred because of a variety of external variations. The movement in 2001 shows that the Daixian county and its adjacent area might be the boundary segment for the relative differential activity. More attention should be paid here.
