The Wenchuan earthquake is a natural disaster. Its occurrence and aftermath have demonstrated the critical roles of seismology and earthquake engineering in reducing seismic hazards and damages. However,their existing...The Wenchuan earthquake is a natural disaster. Its occurrence and aftermath have demonstrated the critical roles of seismology and earthquake engineering in reducing seismic hazards and damages. However,their existing limitations should also be underscored. This article summarized and reviewed the current scientific understanding of earthquake ruptures, and new insights gained since the Wenchuan event. This study focused on the related challenges to seismology and earthquake engineering as follows:(1) The under-estimation of earthquake risks before occurrences.(2) The current limited data regarding large earthquakes in continental thrust fault systems.(3) The causal relationship between the Wenchuan earthquake and the reservoir impoundment in its vicinity.(4) The identification of low-velocity zone in the crust and its seismogenical role.(5) The casualties and economic losses from a cascade of diverse natural hazards triggered by the ruptures, and the excellent earthquake resistance associated with tunnels in mountainous terrain.展开更多
Underground gassy longwall mining goafs may suffer potential gas explosions during the mining process because of the irregularity of gas emissions in the goaf and poor ventilation of the working face,which are risks d...Underground gassy longwall mining goafs may suffer potential gas explosions during the mining process because of the irregularity of gas emissions in the goaf and poor ventilation of the working face,which are risks difficult to control.In this work,the 3235 working face of the Xutuan Colliery in Suzhou City,China,was researched as a case study.The effects of air quantity and gas emission on the three-dimensional distribution of oxygen and methane concentration in the longwall goaf were studied.Based on the revised Coward’s triangle and linear coupling region formula,the coupled methane-oxygen explosive hazard zones(CEHZs)were drawn.Furthermore,a simple practical index was proposed to quantitatively determine the gas explosion risk in the longwall goaf.The results showed that the CEHZs mainly focus on the intake side where the risk of gas explosion is greatest.The CEHZ is reduced with increasing air quantity.Moreover,the higher the gas emission,the larger the CEHZ,which moves towards the intake side at low goaf heights and shifts to the deeper parts of the goaf at high heights.In addition,the risk of gas explosion is reduced as air quantities increase,but when gas emissions increase to a higher level(greater than 50 m3/min),the volume of the CEHZ does not decrease with the increase of air quantity,and the risk of gas explosion no longer shows a linear downward trend.This study is of significance as it seeks to reduce gas explosion accidents and improve mine production safety.展开更多
A probabilistic seismic hazard analysis （PSHA） was conducted to establish the hazard spectra for a site located at Dubai Creek on the west coast of the United Arab Emirates （UAE）. The PSHA considered all the seism...A probabilistic seismic hazard analysis （PSHA） was conducted to establish the hazard spectra for a site located at Dubai Creek on the west coast of the United Arab Emirates （UAE）. The PSHA considered all the seismogenic sources that affect the site, including plate boundaries such as the Makran subduction zone, the Zagros fold-thrust region and the transition fault system between them; and local crustal faults in UAE. PSHA indicated that local faults dominate the hazard. The peak ground acceleration （PGA） for the 475-year return period spectrum is 0.17 g and 0.33 g for the 2,475-year return period spectrum. The hazard spectra are then employed to establish rock ground motions using the spectral matching technique.展开更多
In this article,we review our previous research for spatial and temporal characterizations of the San Andreas Fault(SAF)at Parkfield,using the fault-zone trapped wave(FZTW)since the middle 1980s.Parkfield,California h...In this article,we review our previous research for spatial and temporal characterizations of the San Andreas Fault(SAF)at Parkfield,using the fault-zone trapped wave(FZTW)since the middle 1980s.Parkfield,California has been taken as a scientific seismic experimental site in the USA since the 1970s,and the SAF is the target fault to investigate earthquake physics and forecasting.More than ten types of field experiments(including seismic,geophysical,geochemical,geodetic and so on)have been carried out at this experimental site since then.In the fall of 2003,a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth(SAFOD)site;the main-hole(MH)passed a~200-m-wide low-velocity zone(LVZ)with highly fractured rocks of the SAF at a depth of~3.2 km below the wellhead on the ground level(Hickman et al.,2005;Zoback,2007;Lockner et al.,2011).Borehole seismographs were installed in the SAFOD MH in 2004,which were located within the LVZ of the fault at~3-km depth to probe the internal structure and physical properties of the SAF.On September 282004,a M6 earthquake occurred~15 km southeast of the town of Parkfield.The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake.This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF,California,will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models,the fault models and the earthquake forecasting models in global seismogenic regions.展开更多
The current researches on risk assessment of geological disasters mainly focus on unexpected disasters such as collapses, landslides and mud-rock flows etc. As the convergence zone of land and sea, coastal zone is the...The current researches on risk assessment of geological disasters mainly focus on unexpected disasters such as collapses, landslides and mud-rock flows etc. As the convergence zone of land and sea, coastal zone is the most active and complex area of interactions of lithosphere, hydrosphere, atmosphere, biosphere and anthroposphere. The ecological environment of coastal zone is very fragile, so further systematical research on coastal geological hazard assessment and prevention is in urgent need. The author begins with the definition and research contents and selects three typical coastal geological disasters, namely, the seawater intrusion, coastline change and sea-level rise as the objects of study. The systematic analysis and study on assessment system and methods are conducted, hazard assessment factors are selected, and a completely set of coastal disaster assessment system is established based on the technique of GIS. We took Bao’an District of Shenzhen City as an example and carried out a case study.展开更多
This paper deals with the increasing safety of working in aggressive potential locations, having SCADA system and WSN sensors, using a “probabilistic strategy” in comparison with a “deterministic” one, modeling/si...This paper deals with the increasing safety of working in aggressive potential locations, having SCADA system and WSN sensors, using a “probabilistic strategy” in comparison with a “deterministic” one, modeling/simulation and application in underground coal mining. In general, three conditions can be considered: 1) an unfriendly environment that facilitates the risk of accidents, 2) aggressive equipments that can compete to cause accidents and 3) the work security breaches that can cause accidents. These conditions define the triangle of accidents and are customized for an underground coal mining where the methane gas is released with the exploitation of the massive coal. In this case, the first two conditions create an explosive potential atmosphere. To allow people to work in a safe location it needs: first, a continuing monitoring through SCADA system of the explosive potential atmosphere and second, the use of antiexplosive equipment. This method, named “deterministic strategy”, increases the safety of working, but the explosions have not been completely eliminated. In order to increase the safety of working, the paper continues with the presentation of a new method based on hazard laws, named “probabilistic strategy”. This strategy was validated through modeling/simulation using CupCarbon software platform, and application of WSN networks implemented on Arduino equipments. At the end of the paper the interesting conclusions are emphases which are applicable to both strategies.展开更多
This paper concerns two important environmental problems in China's coastal zone, i.e.,Sea Level Rise (SLR) and Groundwater Table Decline, as the response to climatic chanes/globalwarming due to greenhouse effect....This paper concerns two important environmental problems in China's coastal zone, i.e.,Sea Level Rise (SLR) and Groundwater Table Decline, as the response to climatic chanes/globalwarming due to greenhouse effect. on the basis of possible twacts of these two problems on theregional natural, environmental and social systems, some response strategies were advised.展开更多
In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the ear...In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the earthquake hazard estimation. The declustered catalogues have been compiled from the raw catalogues by deleting the aftershocks in different time interval after main shock according to the criteria for the aftershock activity period. As an example, Hebei seismic zone is taken to show the effect of the aftershock on the earthquake hazard assessment because three strong earthquakes with the aftershocks occurred from 1966 to 1976. The results have been shown that the effect of the aftershocks on the parameters λ m,b is significant. The difference between the clustered and declustered catalogues has reached in seismic activity rate and recurrence period, at most, 45% and 90%, respectively. But the difference in M max is smaller. Based on this, the suggestion that the aftershocks should be omitted in the estimation of the earthquake hazard could be made, but how long the aftershocks activity duration is still left to the future research.展开更多
In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analy...In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analysis of the stress field related to fault strength and behavior is useful for understanding geodynamic processes and conducting hazard assessments.The shallow stress changes after the WCEQ show clear along-strike variations.Degrees of stress orientation rotations have a negative correlation with the horizontal principal stress ratios and the WCEQ apparently reduced the magnitude difference between horizontal principal stresses.Taking stress magnitudes and orientation distribution relative to the fault strike into account,we propose an intermediate-strength of LMSF,with a friction coefficient generally constrained between 0.35 and 0.6.In addition,high-pressure fluids in the fault zone reduce the effective normal stress and to a certain degree weaken the fault strength.The accumulated stress over a certain period following release of the WCEQ indicates the start of another earthquake cycle.The changing crustal stress field makes the LMSF stable or slipping optimally during geodynamic processes.The segmentation feature of the shallow crustal stress field in the LMSF may imply a different tectonic loading and seismic release processes along the fault.The southwestern section to the epicenter of the WCEQ favors the occurrence of future earthquakes,as highμm in a state of critical failure was present in this area,which indicates that the Wenchuan and Lushan earthquakes did not release the accumulated stress to a sufficient extent there.展开更多
A checking on seismic and tsunami hazard for coastal nuclear power plant (NPP) of Chinese continent has been made after Japanese Fukushima nuclear accident caused by earthquake tsunami. The results of the checking are...A checking on seismic and tsunami hazard for coastal nuclear power plant (NPP) of Chinese continent has been made after Japanese Fukushima nuclear accident caused by earthquake tsunami. The results of the checking are introduced briefly in this paper,including the evaluations of seismic and tsunami hazard in NPP siting period,checking results on seismic and tsunami hazard. Because Chinese coastal area belongs to the continental shelf and far from the boundary of plate collision,the tsunami hazard is not significant for coastal area of Chinese continent. However,the effect from tsunami still can't be excluded absolutely since calculated result of Manila trench tsunami source although the tsunami wave is lower than water level from storm surge. The research about earthquake tsunami will continue in future. The tsunami warning system and emergency program of NPP will be established based on principle of defense in depth in China.展开更多
基金funded by the National Natural Science Foundation of China(41790463 and 41674058)
文摘The Wenchuan earthquake is a natural disaster. Its occurrence and aftermath have demonstrated the critical roles of seismology and earthquake engineering in reducing seismic hazards and damages. However,their existing limitations should also be underscored. This article summarized and reviewed the current scientific understanding of earthquake ruptures, and new insights gained since the Wenchuan event. This study focused on the related challenges to seismology and earthquake engineering as follows:(1) The under-estimation of earthquake risks before occurrences.(2) The current limited data regarding large earthquakes in continental thrust fault systems.(3) The causal relationship between the Wenchuan earthquake and the reservoir impoundment in its vicinity.(4) The identification of low-velocity zone in the crust and its seismogenical role.(5) The casualties and economic losses from a cascade of diverse natural hazards triggered by the ruptures, and the excellent earthquake resistance associated with tunnels in mountainous terrain.
基金the National Key Research and Development Program of China(No.2018YFC0808100)the Fundamental Research Funds for the Central Universities(No.2652018098)the Cultivation Fund from the Key Laboratory of Deep Geodrilling Technology,Ministry of Natural Resources(No.PY201902).
文摘Underground gassy longwall mining goafs may suffer potential gas explosions during the mining process because of the irregularity of gas emissions in the goaf and poor ventilation of the working face,which are risks difficult to control.In this work,the 3235 working face of the Xutuan Colliery in Suzhou City,China,was researched as a case study.The effects of air quantity and gas emission on the three-dimensional distribution of oxygen and methane concentration in the longwall goaf were studied.Based on the revised Coward’s triangle and linear coupling region formula,the coupled methane-oxygen explosive hazard zones(CEHZs)were drawn.Furthermore,a simple practical index was proposed to quantitatively determine the gas explosion risk in the longwall goaf.The results showed that the CEHZs mainly focus on the intake side where the risk of gas explosion is greatest.The CEHZ is reduced with increasing air quantity.Moreover,the higher the gas emission,the larger the CEHZ,which moves towards the intake side at low goaf heights and shifts to the deeper parts of the goaf at high heights.In addition,the risk of gas explosion is reduced as air quantities increase,but when gas emissions increase to a higher level(greater than 50 m3/min),the volume of the CEHZ does not decrease with the increase of air quantity,and the risk of gas explosion no longer shows a linear downward trend.This study is of significance as it seeks to reduce gas explosion accidents and improve mine production safety.
文摘A probabilistic seismic hazard analysis （PSHA） was conducted to establish the hazard spectra for a site located at Dubai Creek on the west coast of the United Arab Emirates （UAE）. The PSHA considered all the seismogenic sources that affect the site, including plate boundaries such as the Makran subduction zone, the Zagros fold-thrust region and the transition fault system between them; and local crustal faults in UAE. PSHA indicated that local faults dominate the hazard. The peak ground acceleration （PGA） for the 475-year return period spectrum is 0.17 g and 0.33 g for the 2,475-year return period spectrum. The hazard spectra are then employed to establish rock ground motions using the spectral matching technique.
文摘In this article,we review our previous research for spatial and temporal characterizations of the San Andreas Fault(SAF)at Parkfield,using the fault-zone trapped wave(FZTW)since the middle 1980s.Parkfield,California has been taken as a scientific seismic experimental site in the USA since the 1970s,and the SAF is the target fault to investigate earthquake physics and forecasting.More than ten types of field experiments(including seismic,geophysical,geochemical,geodetic and so on)have been carried out at this experimental site since then.In the fall of 2003,a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth(SAFOD)site;the main-hole(MH)passed a~200-m-wide low-velocity zone(LVZ)with highly fractured rocks of the SAF at a depth of~3.2 km below the wellhead on the ground level(Hickman et al.,2005;Zoback,2007;Lockner et al.,2011).Borehole seismographs were installed in the SAFOD MH in 2004,which were located within the LVZ of the fault at~3-km depth to probe the internal structure and physical properties of the SAF.On September 282004,a M6 earthquake occurred~15 km southeast of the town of Parkfield.The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake.This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF,California,will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models,the fault models and the earthquake forecasting models in global seismogenic regions.
文摘The current researches on risk assessment of geological disasters mainly focus on unexpected disasters such as collapses, landslides and mud-rock flows etc. As the convergence zone of land and sea, coastal zone is the most active and complex area of interactions of lithosphere, hydrosphere, atmosphere, biosphere and anthroposphere. The ecological environment of coastal zone is very fragile, so further systematical research on coastal geological hazard assessment and prevention is in urgent need. The author begins with the definition and research contents and selects three typical coastal geological disasters, namely, the seawater intrusion, coastline change and sea-level rise as the objects of study. The systematic analysis and study on assessment system and methods are conducted, hazard assessment factors are selected, and a completely set of coastal disaster assessment system is established based on the technique of GIS. We took Bao’an District of Shenzhen City as an example and carried out a case study.
文摘This paper deals with the increasing safety of working in aggressive potential locations, having SCADA system and WSN sensors, using a “probabilistic strategy” in comparison with a “deterministic” one, modeling/simulation and application in underground coal mining. In general, three conditions can be considered: 1) an unfriendly environment that facilitates the risk of accidents, 2) aggressive equipments that can compete to cause accidents and 3) the work security breaches that can cause accidents. These conditions define the triangle of accidents and are customized for an underground coal mining where the methane gas is released with the exploitation of the massive coal. In this case, the first two conditions create an explosive potential atmosphere. To allow people to work in a safe location it needs: first, a continuing monitoring through SCADA system of the explosive potential atmosphere and second, the use of antiexplosive equipment. This method, named “deterministic strategy”, increases the safety of working, but the explosions have not been completely eliminated. In order to increase the safety of working, the paper continues with the presentation of a new method based on hazard laws, named “probabilistic strategy”. This strategy was validated through modeling/simulation using CupCarbon software platform, and application of WSN networks implemented on Arduino equipments. At the end of the paper the interesting conclusions are emphases which are applicable to both strategies.
文摘This paper concerns two important environmental problems in China's coastal zone, i.e.,Sea Level Rise (SLR) and Groundwater Table Decline, as the response to climatic chanes/globalwarming due to greenhouse effect. on the basis of possible twacts of these two problems on theregional natural, environmental and social systems, some response strategies were advised.
文摘In this paper, the earthquake hazard parameters (λ m,b and M max) from the maximum likelihood method for the raw catalogue and declustered catalogues have been used to discuss the effect of the aftershocks on the earthquake hazard estimation. The declustered catalogues have been compiled from the raw catalogues by deleting the aftershocks in different time interval after main shock according to the criteria for the aftershock activity period. As an example, Hebei seismic zone is taken to show the effect of the aftershock on the earthquake hazard assessment because three strong earthquakes with the aftershocks occurred from 1966 to 1976. The results have been shown that the effect of the aftershocks on the parameters λ m,b is significant. The difference between the clustered and declustered catalogues has reached in seismic activity rate and recurrence period, at most, 45% and 90%, respectively. But the difference in M max is smaller. Based on this, the suggestion that the aftershocks should be omitted in the estimation of the earthquake hazard could be made, but how long the aftershocks activity duration is still left to the future research.
基金supported by the National Natural Science Foundation of China(Grant No.41702351)the China Geological Survey Project(Grant Nos.DD20211376,DD20221816)。
文摘In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analysis of the stress field related to fault strength and behavior is useful for understanding geodynamic processes and conducting hazard assessments.The shallow stress changes after the WCEQ show clear along-strike variations.Degrees of stress orientation rotations have a negative correlation with the horizontal principal stress ratios and the WCEQ apparently reduced the magnitude difference between horizontal principal stresses.Taking stress magnitudes and orientation distribution relative to the fault strike into account,we propose an intermediate-strength of LMSF,with a friction coefficient generally constrained between 0.35 and 0.6.In addition,high-pressure fluids in the fault zone reduce the effective normal stress and to a certain degree weaken the fault strength.The accumulated stress over a certain period following release of the WCEQ indicates the start of another earthquake cycle.The changing crustal stress field makes the LMSF stable or slipping optimally during geodynamic processes.The segmentation feature of the shallow crustal stress field in the LMSF may imply a different tectonic loading and seismic release processes along the fault.The southwestern section to the epicenter of the WCEQ favors the occurrence of future earthquakes,as highμm in a state of critical failure was present in this area,which indicates that the Wenchuan and Lushan earthquakes did not release the accumulated stress to a sufficient extent there.
文摘A checking on seismic and tsunami hazard for coastal nuclear power plant (NPP) of Chinese continent has been made after Japanese Fukushima nuclear accident caused by earthquake tsunami. The results of the checking are introduced briefly in this paper,including the evaluations of seismic and tsunami hazard in NPP siting period,checking results on seismic and tsunami hazard. Because Chinese coastal area belongs to the continental shelf and far from the boundary of plate collision,the tsunami hazard is not significant for coastal area of Chinese continent. However,the effect from tsunami still can't be excluded absolutely since calculated result of Manila trench tsunami source although the tsunami wave is lower than water level from storm surge. The research about earthquake tsunami will continue in future. The tsunami warning system and emergency program of NPP will be established based on principle of defense in depth in China.
