The knowledge that hydrostatic pressure is equal to the gravity value of the overlying rocks in studying a dynamic state of certain underground site is argued. It is suggested that the stress field T in the crust is a...The knowledge that hydrostatic pressure is equal to the gravity value of the overlying rocks in studying a dynamic state of certain underground site is argued. It is suggested that the stress field T in the crust is a combination or superposition of total hydrostatic pressure P with differential stress σ,and the total hydrostatic pressure P at any point in the crust comprises two parts: one is spherical stress tensor P<sub>G</sub> caused by the gravity, and the other is spherical stress tensor P<sub>s</sub> caused by tectonic stress; therefore P could not be attributed to the gravity of overlying rocks only. The results obtained by a finite-element simulation indicate that the tectono-original additional hydrostatic pressures P<sub>s</sub> decrease gradually from the compressive zone （p<sub>c</sub><sup>S</sup>） to the shear zone (P<sub>SH</sub><sup>s</sup>)and to the tensile zone （P<sub>T</sub><sup>s</sup>）, i.e.P<sub>c</sub><sup>s</sup>】P<sub>sH</sub><sup>s</sup>】P<sub>T</sub><sup>s</sup> in the same depth. On the basis of the above-mentioned research, the method of measurement and calculation of metallogenetic depth corrected by P<sub>s</sub> is展开更多
There are two models of ultrahigh pressure metamorphism (UHPM) zone in Dabie: the model of under thrusting returning which even arrives at the mantle and the superimposed model of tectonics in the crust. There are tw...There are two models of ultrahigh pressure metamorphism (UHPM) zone in Dabie: the model of under thrusting returning which even arrives at the mantle and the superimposed model of tectonics in the crust. There are two points of view in the argument about formation depth of ultrahigh pressure metamorphism: (1) the depth can be calculated by hydrostatic equation; (2) the high pressure was composed of gravity, tectonic and other forces instead of merely gravity force. Some misunderstandings of mechanical conceptions presented in the paper showing the hydrostatic viewpoints should be open to question. The main conceptions are: (1) the confining pressure was only formed by gravity, and the differential stress was only formed by tectonic force; (2) the differential stress is not big enough to lead to form ultrahigh pressure metamorphism; (3) once tectonic overpressure goes beyond the limited strength of rocks the tectonic force would disappear and the rocks would be broken or rheomorphied at the same time. A short discussion in basic mechanics is made in this paper for a perfect process for discussing the argument.展开更多
The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree ...The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electroneg- ativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal-gas system conductivity in an electrostatic field. The quantity of gas adsorbed and AP result from competition between the depth of the adsorption potential well, the coal molecular electronegativ- ity, and the Joule heating effect. △P peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity,△P, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the△P.展开更多
The law of variation of deep rock stress in gravitational and tectonic stress fields is analyzed based on the Hoek-Brown strength criterion. In the gravitational stress field,the rocks in the shallow area are in an el...The law of variation of deep rock stress in gravitational and tectonic stress fields is analyzed based on the Hoek-Brown strength criterion. In the gravitational stress field,the rocks in the shallow area are in an elastic state and the deep,relatively soft rock may be in a plastic state. However,in the tectonic stress field,the relatively soft rock in the shallow area is in a plastic state and the deep rock in an elastic state. A method is proposed to estimate stress values in coal and soft rock based on in-situ measurements of hard rock. Our estimation method relates to the type of stress field and stress state. The equations of rock stress in various stress states are presented for the elastic,plastic and critical states. The critical state is a special stress state,which indicates the conversion of the elastic to the plastic state in the gravitational stress field and the conversion of the plastic to the elastic state in the tectonic stress field. Two cases stud-ies show that the estimation method is feasible.展开更多
Focal depths of the 2008 Ms6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated.Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M≥3.0 were ...Focal depths of the 2008 Ms6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated.Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M≥3.0 were determined using the seismic depth phase sPL;additionally,the focal depths of 232 earthquakes were measured by fitting the threecomponent waveforms of the P and S waves.The source depth of the main shock is^12 km.The majority of the aftershocks with magnitude M≥3.0 occurred in the brittle upper crust at the depths range of 12-18 km.Further,the Source mechanisms of the 232events around the Panzhihua earthquake source area were determined,and the results show that the earthquakes have predominantly strike-slip mechanisms in the Dianzhong Block,but display complexity of the focal mechanisms outside and near the boundary of the Dianzhong block.The 232 earthquake mechanisms from this study are combined with the solutions from the Global Centroid Moment Tensor (GCMT) catalog to derive 2D stress field.The inversion results show that the Dianzhong block is predominantly under a strike slip faulting regime and the direction of the maximum principal compressionσ1 is northwestsoutheast (NW-SE)-trending.The distribution is coincide with GPS velocity field.However,orientations of principal stress axes as well as the faulting types change outside and near the Dianzhong block.The results show that the tectonic stress field in the study area is predominantly controlled by the southeast (SE)-trending horizontal movement and clockwise rotation of the Dianzhong block as a result of the eastward movement of eastern Tibetan meeting the old and rigid South China block (SCB).The Panzhihua earthquake ruptured at^12 km depth where the tectonic stress regime is under the SE-direction horizontal compression and the NE-direction horizontal extension.展开更多
This paper presents some questions to the formula of pressure=depth×specific gravity from the viewpoint that the hydrostatic pressure is equal to the gravity of overlying rocks and the rocks in a static fluid sta...This paper presents some questions to the formula of pressure=depth×specific gravity from the viewpoint that the hydrostatic pressure is equal to the gravity of overlying rocks and the rocks in a static fluid state, which is drawn from the research and analysis of the research field and the corresponding problems of the pressure state in the deep crust and the formation depth of the UHP metamorphic rocks. In this research, the underground rocks are considered as the solid possessing some rheological behaviors to discuss the polysource stress state and to obtain a more reasonable method for the calculation of depths using the model of the unbalanced force solid. It is suggested from this paper that the P/SW method for the calculation of the ultrahigh pressure stemming only from the gravity has obviously overstated the formation depth of the UHP metamorphism. The formation model emphasizing the effect of the gravity, the tectonic force and the metamorphic force of the facies change concludes that such UHP minerals as coesite may have been produced in the inner crust.展开更多
文摘The knowledge that hydrostatic pressure is equal to the gravity value of the overlying rocks in studying a dynamic state of certain underground site is argued. It is suggested that the stress field T in the crust is a combination or superposition of total hydrostatic pressure P with differential stress σ,and the total hydrostatic pressure P at any point in the crust comprises two parts: one is spherical stress tensor P<sub>G</sub> caused by the gravity, and the other is spherical stress tensor P<sub>s</sub> caused by tectonic stress; therefore P could not be attributed to the gravity of overlying rocks only. The results obtained by a finite-element simulation indicate that the tectono-original additional hydrostatic pressures P<sub>s</sub> decrease gradually from the compressive zone （p<sub>c</sub><sup>S</sup>） to the shear zone (P<sub>SH</sub><sup>s</sup>)and to the tensile zone （P<sub>T</sub><sup>s</sup>）, i.e.P<sub>c</sub><sup>s</sup>】P<sub>sH</sub><sup>s</sup>】P<sub>T</sub><sup>s</sup> in the same depth. On the basis of the above-mentioned research, the method of measurement and calculation of metallogenetic depth corrected by P<sub>s</sub> is
文摘There are two models of ultrahigh pressure metamorphism (UHPM) zone in Dabie: the model of under thrusting returning which even arrives at the mantle and the superimposed model of tectonics in the crust. There are two points of view in the argument about formation depth of ultrahigh pressure metamorphism: (1) the depth can be calculated by hydrostatic equation; (2) the high pressure was composed of gravity, tectonic and other forces instead of merely gravity force. Some misunderstandings of mechanical conceptions presented in the paper showing the hydrostatic viewpoints should be open to question. The main conceptions are: (1) the confining pressure was only formed by gravity, and the differential stress was only formed by tectonic force; (2) the differential stress is not big enough to lead to form ultrahigh pressure metamorphism; (3) once tectonic overpressure goes beyond the limited strength of rocks the tectonic force would disappear and the rocks would be broken or rheomorphied at the same time. A short discussion in basic mechanics is made in this paper for a perfect process for discussing the argument.
基金the National Natural Science Foundation of China(No.41272177)the Henan Polytechnic University Doctor Foundation(No.WS2013A11)
文摘The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electroneg- ativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal-gas system conductivity in an electrostatic field. The quantity of gas adsorbed and AP result from competition between the depth of the adsorption potential well, the coal molecular electronegativ- ity, and the Joule heating effect. △P peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity,△P, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the△P.
基金Projects 40272114 and 40572160 supported by the National Natural Science Foundation of China
文摘The law of variation of deep rock stress in gravitational and tectonic stress fields is analyzed based on the Hoek-Brown strength criterion. In the gravitational stress field,the rocks in the shallow area are in an elastic state and the deep,relatively soft rock may be in a plastic state. However,in the tectonic stress field,the relatively soft rock in the shallow area is in a plastic state and the deep rock in an elastic state. A method is proposed to estimate stress values in coal and soft rock based on in-situ measurements of hard rock. Our estimation method relates to the type of stress field and stress state. The equations of rock stress in various stress states are presented for the elastic,plastic and critical states. The critical state is a special stress state,which indicates the conversion of the elastic to the plastic state in the gravitational stress field and the conversion of the plastic to the elastic state in the tectonic stress field. Two cases stud-ies show that the estimation method is feasible.
基金supported by the National Natural Science Foundation of China (Grant No. 41974063)the Basic Research Fund of the Institute of Earthquake Forecasting, China Earthquake Administration (Grant No. 2015IES010302)the State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences (Grant No. SKLGED2018-4-3-E)
文摘Focal depths of the 2008 Ms6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated.Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M≥3.0 were determined using the seismic depth phase sPL;additionally,the focal depths of 232 earthquakes were measured by fitting the threecomponent waveforms of the P and S waves.The source depth of the main shock is^12 km.The majority of the aftershocks with magnitude M≥3.0 occurred in the brittle upper crust at the depths range of 12-18 km.Further,the Source mechanisms of the 232events around the Panzhihua earthquake source area were determined,and the results show that the earthquakes have predominantly strike-slip mechanisms in the Dianzhong Block,but display complexity of the focal mechanisms outside and near the boundary of the Dianzhong block.The 232 earthquake mechanisms from this study are combined with the solutions from the Global Centroid Moment Tensor (GCMT) catalog to derive 2D stress field.The inversion results show that the Dianzhong block is predominantly under a strike slip faulting regime and the direction of the maximum principal compressionσ1 is northwestsoutheast (NW-SE)-trending.The distribution is coincide with GPS velocity field.However,orientations of principal stress axes as well as the faulting types change outside and near the Dianzhong block.The results show that the tectonic stress field in the study area is predominantly controlled by the southeast (SE)-trending horizontal movement and clockwise rotation of the Dianzhong block as a result of the eastward movement of eastern Tibetan meeting the old and rigid South China block (SCB).The Panzhihua earthquake ruptured at^12 km depth where the tectonic stress regime is under the SE-direction horizontal compression and the NE-direction horizontal extension.
文摘This paper presents some questions to the formula of pressure=depth×specific gravity from the viewpoint that the hydrostatic pressure is equal to the gravity of overlying rocks and the rocks in a static fluid state, which is drawn from the research and analysis of the research field and the corresponding problems of the pressure state in the deep crust and the formation depth of the UHP metamorphic rocks. In this research, the underground rocks are considered as the solid possessing some rheological behaviors to discuss the polysource stress state and to obtain a more reasonable method for the calculation of depths using the model of the unbalanced force solid. It is suggested from this paper that the P/SW method for the calculation of the ultrahigh pressure stemming only from the gravity has obviously overstated the formation depth of the UHP metamorphism. The formation model emphasizing the effect of the gravity, the tectonic force and the metamorphic force of the facies change concludes that such UHP minerals as coesite may have been produced in the inner crust.
