Ecological security is a vital problem that people all over the world today have to face and solve, and the situation of ecological security is getting more and more severe and has begun to impede heavily the sustaina...Ecological security is a vital problem that people all over the world today have to face and solve, and the situation of ecological security is getting more and more severe and has begun to impede heavily the sustainable development of social economy. Ecological environment pre-warning has become a hotspot for the modern environment science. This paper introduces the theories of ecological security pre-warning and tries to constitute a pre-warning model of ecological security. In terms of pressure-state-response model, the pre-warning guide line of ecological security is constructed while the pre-warning degree judging model of ecological security is established based on fuzzy optimization. As a case, the model is used to assess the present condition pre-warning of the ecological security of Anhui Province. The result is in correspondence with the real condition: the ecological security situations of 8 cities are dangerous and 9 cities are secure. The result shows that this model is scientific and effective for regional ecological security pre-warning.展开更多
The bolt support quality of coal roadways is one of the important factors for the efficiency and security of coal production. By means of a self-developed technique and equipment of random non-destructive testing, non...The bolt support quality of coal roadways is one of the important factors for the efficiency and security of coal production. By means of a self-developed technique and equipment of random non-destructive testing, non-destructive detection and pre-warning analysis on the quality of bolt support in deep roadways of mining districts were performed in a number of mining areas. The measured data were obtained in the detection instances of abnormal in-situ stress and support invalidation etc. The corresponding relation between axial bolt load variation and roadway surrounding rock deformation and stability was summarized in different mining service stages. Pre-warning technology of roadway surrounding rock stability is proposed based on the detection of axial bolt load. Meanwhile, pre-warning indicators of axial bolt load in different mining service stages are offered and some successful pre-warning cases are also illustrated.The research results show that the change rules of axial bolt load in different mining service stages are quite similar in different mining areas. The change of axial bolt load is in accord with the adjustment of surrounding rock stress, which can consequently reflect the deformation and stability state of roadway surrounding rock. Through the detection of axial bolt load in different sections of roadways, the status of real-time bolt support quality can be reflected; meanwhile, the rationality of bolt support design can be evaluated which provides reference for bolting parameters optimization.展开更多
Aiming at reducing the deficiency of the traditional fire pre-warning algorithms and the intelligent fire pre-warning algorithms such as artificial neural network,and then to improve the accuracy of fire prewarning fo...Aiming at reducing the deficiency of the traditional fire pre-warning algorithms and the intelligent fire pre-warning algorithms such as artificial neural network,and then to improve the accuracy of fire prewarning for high-rise buildings,a composite fire pre-warning controller is designed according to the characteristic（ nonlinear,less historical data,many influence factors）,also a high-rise building fire pre-warning model is set up based on the support vector regression（ SV R）. Then the wood fire standard history data is applied to make empirical analysis. The research results can provide a reliable decision support framework for high-rise building fire pre-warning.展开更多
Pre-warning plays an important role in emergency handling, especially in urban areas with high population density like Beijing. Knowing the information dissemination mechanisms clearly could help us reduce losses and ...Pre-warning plays an important role in emergency handling, especially in urban areas with high population density like Beijing. Knowing the information dissemination mechanisms clearly could help us reduce losses and ensure the safety of human beings during emergencies. In this paper, we propose the models of pre-warning information dissemination via five classical media based on actual pre-warning issue processes, including television, radio, short message service (SMS), electronic screens, and online social networks. The population coverage ability and dissemination efficiency at different issue time of these five issue channels are analyzed by simulation methods, and their advantages and disadvantages are compared by radar graphs. Results show that SMS is the most appropriate way to issue long-term pre-warning for its large population coverage, but it is not suitable for issuing urgent warnings to large population because of the limitation of telecom company's issue ability. TV shows the best performance to combine the dissemination speed and range, and the performance of radio and electronic screens are not as satisfactory as the others. In addition, online social networks might become one of the most promising communication method for its potential in further diffusion. These models and results could help us make pre-warning issue plans and provide guidance for future construction of information diffusion systems, thus reducing injuries, deaths, and other losses under different emergencies.展开更多
In order to accurately test gas concentration and effectively pre-waming when the gas concentration over-limited on work face, used the high-performance and low prices SCM and the low-cost and high transfer efficiency...In order to accurately test gas concentration and effectively pre-waming when the gas concentration over-limited on work face, used the high-performance and low prices SCM and the low-cost and high transfer efficiency bluetooth technology to forecast the gas concentration in real time. The data tested by SCM, then got the corresponding mathematical model of the data. Put forward the idea of using fuzzy structured element theory to dynamic forecast the gas concentration, analyzed the features in abnormal-effusing on work face and judge whether there was the possibility of abnormal gas-effusion. Simulation results show that mathematical model of this system about gas concentration is correct. This system changes coal mine monitoring system＇s traditional way of after-alarming into early-warning, and thus enhances its feasibility.展开更多
This paper summarized theory discussion,main research methods,contents,empirical and engineering researches of farmland prewarning in China.It stated that future researches of farmland pre-warning in China will focus ...This paper summarized theory discussion,main research methods,contents,empirical and engineering researches of farmland prewarning in China.It stated that future researches of farmland pre-warning in China will focus on deepening application of farmland security prewarning models,revealing mechanism of changes in different farmland resources,establishing pre-warning models suitable for research areas,accurate evaluation and prediction of farmland security,and exploring establishing and improving farmland security monitoring system and operating mechanism of all levels.展开更多
In this study, we analyze whether there is a change in driver actions because of voice navigation information provided by utilizing ITS （intelligent transport systems）. Specifically, when a vehicle approaches a sign...In this study, we analyze whether there is a change in driver actions because of voice navigation information provided by utilizing ITS （intelligent transport systems）. Specifically, when a vehicle approaches a signalized intersection, the driver is provided with the voice navigation information that the signal light will shortly change red. We focus on what is effective when the voice navigation information is provided. Even if the timing of the provision of voice information is delayed, we have evaluated whether the vehicle is able to stop safely. From the results of the analysis, by providing voice navigation information, we know that a vehicle will stop safely at a signalized intersection. Even if the information provided by voice navigation has been delayed, it could be shown to be safe compared with the case where no information was provided.展开更多
To quantitatively reveal how rock blocks falling into water affect the impulse waves,the influence of a rigid block on induced first wave and second wave is systematically investigated.The block characteristics includ...To quantitatively reveal how rock blocks falling into water affect the impulse waves,the influence of a rigid block on induced first wave and second wave is systematically investigated.The block characteristics include the initial velocity,density,volume,and incident angle,and the investigated wave behavior characteristics include the maximum kinetic energy of the water,the transformation ratio of the kinetic energy from the block to the waves,the duration of the waves,the maximum movement speed,and the maximum height and width of the waves.The coupled Eulerian-Lagrangian method(CEL)is introduced to establish the numerical models of the fluid-solid coupling,and a laboratory test of a rigid wedge sliding into water demonstrates that it can reasonably describe the dynamic behavior of a landslide-induced wave.A typical process of a block entering water and its energy variation are described and analyzed in detail.Further,the relationship between each characteristic parameter of the block and the waves is quantitatively investigated and fitted.The simulation results show that energy exchange between the block and the water is very rapid after the block collides with the water.The maximum kinetic energy,maximum velocity,duration,and side dimension of the waves mainly increase non-linearly with the above characteristic parameters of the block.The transformation ratio of the kinetic energy from the block to the water,the first wave,and the second wave are usually below 60%,45%,and 30%,respectively.The velocity of the block first decreases and then maintains a constant speed after entering the water.The displacement of the block increases linearly with the initial velocity and density of the block and exponentially increases with the block volume at different times.With the increase in the incident angle of the block,the kinetic energy and scale of the second wave increase correspondingly.展开更多
Mangroves are crucial for protecting coastal areas against extreme disasters such as tsunamis and storm surges.An experimental study was conducted to determine how mangroves can mitigate the tsunami wave propagation.T...Mangroves are crucial for protecting coastal areas against extreme disasters such as tsunamis and storm surges.An experimental study was conducted to determine how mangroves can mitigate the tsunami wave propagation.The test was performed in a flume, where mangrove models were installed on a slope, and dam-burst waves were used to simulate tsunami waves. To study how mangrove forests reduce the impact of tsunamis, this paper measured the heights of the incoming waves under different initial conditions(tsunami wave intensity and initial water depth) and plant factors(arrangement and distribution density) and described the reduction process. The results show that, after passing through the mangrove, the tsunami bore height will decrease within a certain range as the initial water depth increases. However, there is no correlation between the increase of inundation level and the drop of water level. The bore height attenuation is more significant at higher density of mangroves,but after tsunami passing through the mangroves, the relative bore height will decrease. When the distribution density of mangroves is constant, the wave attenuation at different locations(before, on and after the slope)shows different relationships with the initial water depth and wave height for different models. The transmission coefficient(K_(i)) shows a parabolic correlation with its density. The proportion of the energy loss caused by the mangrove resistance to the total energy(E_(b)) is defined as C_(m2). The variation trend of C_(m2) corresponds to the tsunami wave energy attenuation rate(C_(a)) and K_(i).展开更多
To assist the analysis of tsunami hazards for Qatar coastal areas were using numerical model. By Tsunamis waves created from submarine earthquakes of magnitude of (M<sub>w</sub>) 8.6 and 9.0 in Richard sca...To assist the analysis of tsunami hazards for Qatar coastal areas were using numerical model. By Tsunamis waves created from submarine earthquakes of magnitude of (M<sub>w</sub>) 8.6 and 9.0 in Richard scale along the Makran Subduction Zone (MSZ) as well as coastal landslides with soil volume of 1.25 to 2.0 km<sup>3</sup> along Iranian coast inside the Arabian Gulf is considered. TUNAMI-N2KISR model (Al-Salem) was applied in this study to predict the tsunami propagation and magnitude of Tsunami induced wave heights. The model adopts to solve shallow water equations describing nonlinear long-wave theory. The model also incorporate tidal effect inside the Arabian Gulf as a tsunami travel time from Makran Subduction to Qatar coastline takes more than 9 hours with the tidal range of about 1.6 m during Spring Tide event. For coastal landslides, tsunami generation was simulated using a two-layer numerical model, developed by solving nonlinear long-wave equations. Two-layer model was used to determine initial wave deformation generated by a landslide case. Then TUNAMI-N2KISR was use to simulate tsunami wave propagation. Tsunami waves from landslide scenario arrived after 2.5 - 3 hr with maximum tsunami amplitudes along coasts of Ras laffan-Qatar were 0.8 to 1.0 m. Incorporation of ocean tide is found to impose some small effect on tsunami amplitude at Qatar coastline and nearby areas for the Mw 9.0 earthquake due to small tidal range in this area. In addition, it is found that the tsunami arrival time has become shorter.展开更多
In this study,the Radio Direction Finding method is proposed for the detection of electromagnetic signals,in the VLF band,to try to anticipate the occurrence of potentially destructive geophysical events.The experimen...In this study,the Radio Direction Finding method is proposed for the detection of electromagnetic signals,in the VLF band,to try to anticipate the occurrence of potentially destructive geophysical events.The experimentation concerns the interception of electromagnetic anomalies in Sierra Leone,in the five-day time window,associated with seismic events that could potentially generate tsunamis.The area of investigation is Sierra Leone,whose coastline is subjected to tidal wave hazards triggered by earthquakes generated in the Mid-Atlantic Ridge.Although Sierra Leone is not affected by recurrent earthquakes,there is nevertheless a low probability,estimated at 2 percent,of the occurrence of destructive earthquakes in the next 50 years.Also in estimates,the risk of rogue and potentially damaging waves is estimated to strike the Sierra Leone coast at least once in the next 10 years.The Radio Direction Finding experiment carried out continuously 24/7,has shown a close relationship between increased radio-anomalies,in the frequencies of 6,000 Hz,a time window between electromagnetic anomaly detection and the imminence of an earthquake,and higher frequency times for the risk of earthquake occurrence in the Mid-Atlantic Ridge.展开更多
Tsunami induced by earthquake is an interaction problem between liquid and solid.Shallow-water wave equation is often used to modeling the tsunami,and the boundary or initial condition of the problem is determined by ...Tsunami induced by earthquake is an interaction problem between liquid and solid.Shallow-water wave equation is often used to modeling the tsunami,and the boundary or initial condition of the problem is determined by the displacement or velocity field from the earthquake under sea floor,usually no interaction between them is consid-ered in pure liquid model.In this study,the potential flow theory and the finite element method with the interaction between liquid and solid are employed to model the dynamic processes of the earthquake and tsunami.For model-ing the earthquake,firstly the initial stress field to generate the earthquake is set up,and then the occurrence of the earthquake is simulated by suddenly reducing the elastic material parameters inside the earthquake fault.It is dif-ferent from seismic dislocation theory in which the relative slip on the fault is specified in advance.The modeling results reveal that P,SP and the surface wave can be found at the sea surface besides the tsunami wave.The surface wave arrives at the distance of 600 km from the epicenter earlier than the tsunami 48 minutes,and its maximum amplitude is 0.55 m,which is 2 times as large as that of the sea floor.Tsunami warning information can be taken from the surface wave on the sea surface,which is much earlier than that obtained from the seismograph stations on land.The tsunami speed on the open sea with 3 km depth is 175.8 m/s,which is a little greater than that pre-dicted by long wave theory,(gh)1/2=171.5 m,and its wavelength and amplitude in average are 32 km and 2 m,respectively.After the tsunami propagates to the continental shelf,its speed and wavelength is reduced,but its amplitude become greater,especially,it can elevate up to 10 m and run 55 m forward in vertical and horizontal directions at sea shore,respectively.The maximum vertical accelerations at the epicenter on the sea surface and on the earthquake fault are 5.9 m/s2 and 16.5 m/s2,respectively,the later is 2.8 times the former,and therefore,sea water is a good shock absorber.The acceleration at the sea shore is about 1/10 as large as at the epicenter.The maximum vertical velocity at the epicenter is 1.4 times that on the fault.The maximum vertical displacement at the fault is less than that at the epicenter.The difference between them is the amplitude of the tsunami at the epicenter.The time of the maximum displacement to occur on the fault is not at the beginning of the fault slipping but retards 23 s.展开更多
基金Undertheauspicesof China Postdoctoral Science Foundation (No.2004035175), and the Natural Science Founda-tionof Anhui Provincial Bureau of Education (No.2003KJ043ZD)
文摘Ecological security is a vital problem that people all over the world today have to face and solve, and the situation of ecological security is getting more and more severe and has begun to impede heavily the sustainable development of social economy. Ecological environment pre-warning has become a hotspot for the modern environment science. This paper introduces the theories of ecological security pre-warning and tries to constitute a pre-warning model of ecological security. In terms of pressure-state-response model, the pre-warning guide line of ecological security is constructed while the pre-warning degree judging model of ecological security is established based on fuzzy optimization. As a case, the model is used to assess the present condition pre-warning of the ecological security of Anhui Province. The result is in correspondence with the real condition: the ecological security situations of 8 cities are dangerous and 9 cities are secure. The result shows that this model is scientific and effective for regional ecological security pre-warning.
基金the State Key Research Development Program of China(No.2016YFC0600705)the Fundamental Research Funds for the Central Universities(No.2015XKZD06)+1 种基金the National Natural Science Foundation of China(Nos.51227003,51404250,51504243,51474215,51404262 and 51323004)the Natural Science Foundation of Jiangsu Province,China(Nos.BK20150191 and BK20140213)
文摘The bolt support quality of coal roadways is one of the important factors for the efficiency and security of coal production. By means of a self-developed technique and equipment of random non-destructive testing, non-destructive detection and pre-warning analysis on the quality of bolt support in deep roadways of mining districts were performed in a number of mining areas. The measured data were obtained in the detection instances of abnormal in-situ stress and support invalidation etc. The corresponding relation between axial bolt load variation and roadway surrounding rock deformation and stability was summarized in different mining service stages. Pre-warning technology of roadway surrounding rock stability is proposed based on the detection of axial bolt load. Meanwhile, pre-warning indicators of axial bolt load in different mining service stages are offered and some successful pre-warning cases are also illustrated.The research results show that the change rules of axial bolt load in different mining service stages are quite similar in different mining areas. The change of axial bolt load is in accord with the adjustment of surrounding rock stress, which can consequently reflect the deformation and stability state of roadway surrounding rock. Through the detection of axial bolt load in different sections of roadways, the status of real-time bolt support quality can be reflected; meanwhile, the rationality of bolt support design can be evaluated which provides reference for bolting parameters optimization.
基金Supported by the National Natural Science Foundation of China(11072035)
文摘Aiming at reducing the deficiency of the traditional fire pre-warning algorithms and the intelligent fire pre-warning algorithms such as artificial neural network,and then to improve the accuracy of fire prewarning for high-rise buildings,a composite fire pre-warning controller is designed according to the characteristic（ nonlinear,less historical data,many influence factors）,also a high-rise building fire pre-warning model is set up based on the support vector regression（ SV R）. Then the wood fire standard history data is applied to make empirical analysis. The research results can provide a reliable decision support framework for high-rise building fire pre-warning.
基金Project supported by the Science Fund from the Ministry of Science and Technology of China(Grant No.2018YFC0807000).
文摘Pre-warning plays an important role in emergency handling, especially in urban areas with high population density like Beijing. Knowing the information dissemination mechanisms clearly could help us reduce losses and ensure the safety of human beings during emergencies. In this paper, we propose the models of pre-warning information dissemination via five classical media based on actual pre-warning issue processes, including television, radio, short message service (SMS), electronic screens, and online social networks. The population coverage ability and dissemination efficiency at different issue time of these five issue channels are analyzed by simulation methods, and their advantages and disadvantages are compared by radar graphs. Results show that SMS is the most appropriate way to issue long-term pre-warning for its large population coverage, but it is not suitable for issuing urgent warnings to large population because of the limitation of telecom company's issue ability. TV shows the best performance to combine the dissemination speed and range, and the performance of radio and electronic screens are not as satisfactory as the others. In addition, online social networks might become one of the most promising communication method for its potential in further diffusion. These models and results could help us make pre-warning issue plans and provide guidance for future construction of information diffusion systems, thus reducing injuries, deaths, and other losses under different emergencies.
文摘In order to accurately test gas concentration and effectively pre-waming when the gas concentration over-limited on work face, used the high-performance and low prices SCM and the low-cost and high transfer efficiency bluetooth technology to forecast the gas concentration in real time. The data tested by SCM, then got the corresponding mathematical model of the data. Put forward the idea of using fuzzy structured element theory to dynamic forecast the gas concentration, analyzed the features in abnormal-effusing on work face and judge whether there was the possibility of abnormal gas-effusion. Simulation results show that mathematical model of this system about gas concentration is correct. This system changes coal mine monitoring system＇s traditional way of after-alarming into early-warning, and thus enhances its feasibility.
文摘This paper summarized theory discussion,main research methods,contents,empirical and engineering researches of farmland prewarning in China.It stated that future researches of farmland pre-warning in China will focus on deepening application of farmland security prewarning models,revealing mechanism of changes in different farmland resources,establishing pre-warning models suitable for research areas,accurate evaluation and prediction of farmland security,and exploring establishing and improving farmland security monitoring system and operating mechanism of all levels.
文摘In this study, we analyze whether there is a change in driver actions because of voice navigation information provided by utilizing ITS （intelligent transport systems）. Specifically, when a vehicle approaches a signalized intersection, the driver is provided with the voice navigation information that the signal light will shortly change red. We focus on what is effective when the voice navigation information is provided. Even if the timing of the provision of voice information is delayed, we have evaluated whether the vehicle is able to stop safely. From the results of the analysis, by providing voice navigation information, we know that a vehicle will stop safely at a signalized intersection. Even if the information provided by voice navigation has been delayed, it could be shown to be safe compared with the case where no information was provided.
基金funded by the Second Tibetan Plateau Scientific Expedition and Research Program (STEP) (Grant No. 2021QZKK0202)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA20030301)+1 种基金the National Natural Science Foundation (Grant No. 41790432 and U22A20603)the fellowship of China Postdoctoral Science Foundation (Grant No. 2020M683369)
文摘To quantitatively reveal how rock blocks falling into water affect the impulse waves,the influence of a rigid block on induced first wave and second wave is systematically investigated.The block characteristics include the initial velocity,density,volume,and incident angle,and the investigated wave behavior characteristics include the maximum kinetic energy of the water,the transformation ratio of the kinetic energy from the block to the waves,the duration of the waves,the maximum movement speed,and the maximum height and width of the waves.The coupled Eulerian-Lagrangian method(CEL)is introduced to establish the numerical models of the fluid-solid coupling,and a laboratory test of a rigid wedge sliding into water demonstrates that it can reasonably describe the dynamic behavior of a landslide-induced wave.A typical process of a block entering water and its energy variation are described and analyzed in detail.Further,the relationship between each characteristic parameter of the block and the waves is quantitatively investigated and fitted.The simulation results show that energy exchange between the block and the water is very rapid after the block collides with the water.The maximum kinetic energy,maximum velocity,duration,and side dimension of the waves mainly increase non-linearly with the above characteristic parameters of the block.The transformation ratio of the kinetic energy from the block to the water,the first wave,and the second wave are usually below 60%,45%,and 30%,respectively.The velocity of the block first decreases and then maintains a constant speed after entering the water.The displacement of the block increases linearly with the initial velocity and density of the block and exponentially increases with the block volume at different times.With the increase in the incident angle of the block,the kinetic energy and scale of the second wave increase correspondingly.
基金The National Natural Science Foundation of China under contract Nos 51809047 and U22A20585the Fujian Provincial Natural Science Foundation under contract No.2019J05029.
文摘Mangroves are crucial for protecting coastal areas against extreme disasters such as tsunamis and storm surges.An experimental study was conducted to determine how mangroves can mitigate the tsunami wave propagation.The test was performed in a flume, where mangrove models were installed on a slope, and dam-burst waves were used to simulate tsunami waves. To study how mangrove forests reduce the impact of tsunamis, this paper measured the heights of the incoming waves under different initial conditions(tsunami wave intensity and initial water depth) and plant factors(arrangement and distribution density) and described the reduction process. The results show that, after passing through the mangrove, the tsunami bore height will decrease within a certain range as the initial water depth increases. However, there is no correlation between the increase of inundation level and the drop of water level. The bore height attenuation is more significant at higher density of mangroves,but after tsunami passing through the mangroves, the relative bore height will decrease. When the distribution density of mangroves is constant, the wave attenuation at different locations(before, on and after the slope)shows different relationships with the initial water depth and wave height for different models. The transmission coefficient(K_(i)) shows a parabolic correlation with its density. The proportion of the energy loss caused by the mangrove resistance to the total energy(E_(b)) is defined as C_(m2). The variation trend of C_(m2) corresponds to the tsunami wave energy attenuation rate(C_(a)) and K_(i).
文摘To assist the analysis of tsunami hazards for Qatar coastal areas were using numerical model. By Tsunamis waves created from submarine earthquakes of magnitude of (M<sub>w</sub>) 8.6 and 9.0 in Richard scale along the Makran Subduction Zone (MSZ) as well as coastal landslides with soil volume of 1.25 to 2.0 km<sup>3</sup> along Iranian coast inside the Arabian Gulf is considered. TUNAMI-N2KISR model (Al-Salem) was applied in this study to predict the tsunami propagation and magnitude of Tsunami induced wave heights. The model adopts to solve shallow water equations describing nonlinear long-wave theory. The model also incorporate tidal effect inside the Arabian Gulf as a tsunami travel time from Makran Subduction to Qatar coastline takes more than 9 hours with the tidal range of about 1.6 m during Spring Tide event. For coastal landslides, tsunami generation was simulated using a two-layer numerical model, developed by solving nonlinear long-wave equations. Two-layer model was used to determine initial wave deformation generated by a landslide case. Then TUNAMI-N2KISR was use to simulate tsunami wave propagation. Tsunami waves from landslide scenario arrived after 2.5 - 3 hr with maximum tsunami amplitudes along coasts of Ras laffan-Qatar were 0.8 to 1.0 m. Incorporation of ocean tide is found to impose some small effect on tsunami amplitude at Qatar coastline and nearby areas for the Mw 9.0 earthquake due to small tidal range in this area. In addition, it is found that the tsunami arrival time has become shorter.
文摘In this study,the Radio Direction Finding method is proposed for the detection of electromagnetic signals,in the VLF band,to try to anticipate the occurrence of potentially destructive geophysical events.The experimentation concerns the interception of electromagnetic anomalies in Sierra Leone,in the five-day time window,associated with seismic events that could potentially generate tsunamis.The area of investigation is Sierra Leone,whose coastline is subjected to tidal wave hazards triggered by earthquakes generated in the Mid-Atlantic Ridge.Although Sierra Leone is not affected by recurrent earthquakes,there is nevertheless a low probability,estimated at 2 percent,of the occurrence of destructive earthquakes in the next 50 years.Also in estimates,the risk of rogue and potentially damaging waves is estimated to strike the Sierra Leone coast at least once in the next 10 years.The Radio Direction Finding experiment carried out continuously 24/7,has shown a close relationship between increased radio-anomalies,in the frequencies of 6,000 Hz,a time window between electromagnetic anomaly detection and the imminence of an earthquake,and higher frequency times for the risk of earthquake occurrence in the Mid-Atlantic Ridge.
基金National Natural Science Foundation of China (40521002 and 40474013).
文摘Tsunami induced by earthquake is an interaction problem between liquid and solid.Shallow-water wave equation is often used to modeling the tsunami,and the boundary or initial condition of the problem is determined by the displacement or velocity field from the earthquake under sea floor,usually no interaction between them is consid-ered in pure liquid model.In this study,the potential flow theory and the finite element method with the interaction between liquid and solid are employed to model the dynamic processes of the earthquake and tsunami.For model-ing the earthquake,firstly the initial stress field to generate the earthquake is set up,and then the occurrence of the earthquake is simulated by suddenly reducing the elastic material parameters inside the earthquake fault.It is dif-ferent from seismic dislocation theory in which the relative slip on the fault is specified in advance.The modeling results reveal that P,SP and the surface wave can be found at the sea surface besides the tsunami wave.The surface wave arrives at the distance of 600 km from the epicenter earlier than the tsunami 48 minutes,and its maximum amplitude is 0.55 m,which is 2 times as large as that of the sea floor.Tsunami warning information can be taken from the surface wave on the sea surface,which is much earlier than that obtained from the seismograph stations on land.The tsunami speed on the open sea with 3 km depth is 175.8 m/s,which is a little greater than that pre-dicted by long wave theory,(gh)1/2=171.5 m,and its wavelength and amplitude in average are 32 km and 2 m,respectively.After the tsunami propagates to the continental shelf,its speed and wavelength is reduced,but its amplitude become greater,especially,it can elevate up to 10 m and run 55 m forward in vertical and horizontal directions at sea shore,respectively.The maximum vertical accelerations at the epicenter on the sea surface and on the earthquake fault are 5.9 m/s2 and 16.5 m/s2,respectively,the later is 2.8 times the former,and therefore,sea water is a good shock absorber.The acceleration at the sea shore is about 1/10 as large as at the epicenter.The maximum vertical velocity at the epicenter is 1.4 times that on the fault.The maximum vertical displacement at the fault is less than that at the epicenter.The difference between them is the amplitude of the tsunami at the epicenter.The time of the maximum displacement to occur on the fault is not at the beginning of the fault slipping but retards 23 s.
