Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits base...Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits based on high-resolution satellite images.Therefore,we provide a framework for extracting liquefaction pits based on a case-based reasoning method.Furthermore,five covariates selection methods were used to filter the 11 covariates that were generated from high-resolution satellite images and digital elevation models(DEM).The proposed method was trained with 450 typical samples which were collected based on visual interpretation,then used the trained case-based reasoning method to identify the liquefaction pits in the whole study area.The performance of the proposed methods was evaluated from three aspects,the prediction accuracies of liquefaction pits based on the validation samples by kappa index,the comparison between the pre-and post-earthquake images,the rationality of spatial distribution of liquefaction pits.The final result shows the importance of covariates ranked by different methods could be different.However,the most important of covariates is consistent.When selecting five most important covariates,the value of kappa index could be about 96%.There also exist clear differences between the pre-and post-earthquake areas that were identified as liquefaction pits.The predicted spatial distribution of liquefaction is also consistent with the formation principle of liquefaction.展开更多
Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and respons...Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.展开更多
An M_(S)6.4 earthquake occurred near Yangbi County, Dali Bai Autonomous Prefecture, Yunnan Province, at 21:48on May 21, 2021. The earthquake location is characterized by complex geological structures, with multiple ac...An M_(S)6.4 earthquake occurred near Yangbi County, Dali Bai Autonomous Prefecture, Yunnan Province, at 21:48on May 21, 2021. The earthquake location is characterized by complex geological structures, with multiple active faults distributed around the epicenter that is located at the west edge of the Sichuan-Yunnan rhombic block(25.67°N, 99.87°E). A total of 42 ground cracks are found by earthquake field investigations. The cracks are mainly concentrated in the Ⅷ degree area on the west side of the Yangbi River. Among these, 9 coseismic tectonic ground cracks generated by shear fractures are found in three villages(i.e., Akechang, Meijia-Lijia, and Huajiazhuang), which are distributed along the strike of the northwest-trending linear folds, showing the tectonic characteristics of right-lateral tension or left-stepping cracks. The structural attribute of ground cracks sustains the kinematic properties of the Weixi-Qiaohou fault, namely right-lateral strike-slip.展开更多
According to volume 18(Xuanzong Ji Tang)of the historical book entitled the Old Book of Tang,the Hetao area of Inner Mongolia experienced a large earthquake in AD 849.However,previous work on that earthquake contains ...According to volume 18(Xuanzong Ji Tang)of the historical book entitled the Old Book of Tang,the Hetao area of Inner Mongolia experienced a large earthquake in AD 849.However,previous work on that earthquake contains many discrepancies regarding its epicenter location,magnitude,deaths,and intensity.While exploring active faults in Baotou City,the present authors mapped the Daqing Mountain piedmont fault geologically.Based on previous work,several seismic deformation traces of more than 1000 years ago were found,and dating tests were conducted.The research showed the Daqing Mountain piedmont fault zone to be the seismogenic structure of the AD 849 earthquake.The length of earthquake surface rupture zone was around 80 km,and the macro epicenter was located in the active fault.The deformation center was located at 40.6°N,110.2°E.By collecting and analyzing more historical data about the AD 849 earthquake,reinterpreting some existing historical data,and re-examining the contradictory numbers of deaths in the historical data,the present analysis concludes that around 10,000 people were dead.It is suggested that this earthquake had a magnitude of 7½.According to the revised seismic parameters and the paleoearthquake recurrence period of the Daqing Mountain piedmont fault,the boundary of some potential seismic sources zone in the Baotou area are adjusted and the recurrence period of M8 and M7.5 are re-calculated.展开更多
According to the results of estimation of the maximum potential earthquake in the project of "The Active Fault Detection and Seismic Risk Evaluation( Phase II) of Zhengzhou City",the near east-west trending ...According to the results of estimation of the maximum potential earthquake in the project of "The Active Fault Detection and Seismic Risk Evaluation( Phase II) of Zhengzhou City",the near east-west trending Laoyachen fault and Shangjie fault are developed in the urban area.The Laoyachen fault was not active in the Quaternary,but the Shangjie fault may have the potential of generating M5.0~5.5 earthquakes.In order to get the probability of occurrence of maximum potential earthquakes,we delineate the statistical areas and the potential source areas and calculate the seismicity parameters and the space distribution functions.Our study shows that the probability of occurrence of an earthquake with M≥5.0 on the faults in Zhengzhou city is 6% in the next 50 years and 11% in the next 100years.展开更多
According to field investigation and interpretation of remote sensing images,the north segment of the Longling-Ruili fault is a Holocene dextral strike-slip fault with a small amount of normal faulting.Based on large-...According to field investigation and interpretation of remote sensing images,the north segment of the Longling-Ruili fault is a Holocene dextral strike-slip fault with a small amount of normal faulting.Based on large-scale geological mapping at some typical locations and quantitative geomorphologic deformation measurement and dating analysis,this fault is a Holocene active fault.The strike-slip rate of the Longling-Ruili fault is 2.2 ~2.5mm / a and vertical slip rate is 0.6mm /a since the late Pleistocene epoch.The strike-slip rate of the Longling-Ruili fault is 1.8~3.0mm /a and vertical slip rate is 0.5mm /a since the Holocene epoch.Based on the Poisson model,lognormal model and BPT model,the occurrence probability of strong earthquakes in 50 years is estimated to be 6.32%,0.08%and 0.05%,respectively.Then,a 1.82% probability of occurrence of characteristic earthquake for the north segment of the Longling-Ruili fault is obtained by setting a weight of 0.28,0.36 and 0.36 to the Poisson model,lognormal model and BPT model,respectively.展开更多
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
The coseismic surface rupture zone of the seismogenic fault of the MS7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°~320°, in general. An approximately 2km-long en echelon ten...The coseismic surface rupture zone of the seismogenic fault of the MS7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°~320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9km long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.展开更多
The M8.0 Wenchuan earthquake occurred on the Longmenshan fault zone. Based on field investigation of the surface rupture and focal mechanism study of the aftershocks, we discuss the geological relationship of the main...The M8.0 Wenchuan earthquake occurred on the Longmenshan fault zone. Based on field investigation of the surface rupture and focal mechanism study of the aftershocks, we discuss the geological relationship of the main, secondary and triggered ruptures. The main rupture is about 200km long and can be divided into the south part and the north part. The south part consists of two parallel fault zones characterized by reverse faulting, with several parallel secondary ruptures on the hanging wall of the main fault, and the north part is a single main fault zone characterized by lateral strike-slip and reverse faulting. Compared to a 300km long aftershock distribution, the surface rupture only occupies 200km, and the remaining 100km on the northeast of the main rupture was triggered by aftershocks. Study on the ruptures of this earthquake will be useful for studying the earthquake risk evolution on the Longmenshan fault system.展开更多
Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the ev...Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the evolution of the Yuguang Basin South Margin Fault (YBSMF) in northwest Beijing was carried out. We found that the propagation and growth of faults most often occurred often at two locations: the fault overlapping zone and the uneven or rough fault segment. Through detailed observation and analysis of all cropouts of faults along the YBSMF from zone a to zone i, we identified three major factors that dominate or affect fault propagation and growth. First, the irregularity of fault geometry determine the propagation and growth of the fault, and therefore, the faults always propagate and grow at such irregular fault segments. The fault finally cuts off and eliminates its irregularity, making the fault geometry and fault plane smoother than before, which contributes to the slipping movement of the half-graben block in the basin. Second, the scale of the irregularity of the fault geometry affects the result of fault propagation and growth, that is, the degree of the cutting off of fault irregularity. The degree of cutting off decreases as irregularity scale increases. Third, the maximum possible slip displacement of the fault segment influences the duration of fault propagation and growth. The duration at the central segments with a large slip displacement is longer than that at the end segments with a smaller slippage value.展开更多
This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,China.Emphasis is placed on the ...This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,China.Emphasis is placed on the major factors for predominating the dynamic shear modulus(G)and damping ratio(λ)in the shear strain amplitude(γ_(a))from 10^(-5) to 10^(-2),involving depth,sedimentary facies types,and water content of marine soils.The empirical equations of the small-strain shear modulus(G_(max))and damping ratio(λ_(min))using a single-variable of depth H are established for the three marine soils.A remarkable finding is that the curves of shear modulus reduction(G/G_(max))and the damping ratio(λ)with increasing γ_(a) of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content W.This finding is validated by independent experimental data from the literature.At the similar depths,the G value of the marine soils of terrestrial facies is the largest,followed b_(y) the neritic facies,and the G value of the marine soils of abyssal facies is the smallest.The sedimentary facies types of the marine soils have slight effect on theλvalue.Another significant finding is that the shear modulus reduction curves plotted against the γ_(a) of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils,while the damping curves plotted against γ_(a) are just the opposite.The results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data.展开更多
Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear an...Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear analytical model for Fuzhou Basin was established.The peak ground motion acceleration(PGA) and focusing effect with depth were analyzed.Meanwhile,the results by wave propagation of one-dimensional(1D) layered medium equivalent linearization method were added for contrast.The results show that:1) PGA at different depths are obviously amplified compared to the input ground motion,amplification effect of both funnel-shaped depression and upheaval areas(based on the shape of bedrock surface) present especially remarkable.The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers,while the 1D results turn out that the PGA decreases with depth,except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas,PGA amplification effect above 8 m depth shows relatively larger,to the upheaval areas,PGA amplification effect from 15 m to 25 m depth seems more significant.However,the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.展开更多
By expressing the wave functions in the form of Fourier-Bessel series, the analytical solution for the two-dimension scattering problem of plane P waves by the cylindrical canyon topography that contains arbitrary num...By expressing the wave functions in the form of Fourier-Bessel series, the analytical solution for the two-dimension scattering problem of plane P waves by the cylindrical canyon topography that contains arbitrary number of circular-arc-shaped layers is presented firstly. And then, the convergence of the proposed series solution with the truncation number of terms is discussed, which demonstrates that the analytical solution can converge even for very high frequencies of the incident P wave. Finally, using this solution, the influences that are imposed on the stationary ground motion by the number and the sequence of alluvial layers, as well as the stiffness of soft interlayer contained in the canyon, are studied,展开更多
A one-dimensional equivalent linear method (EQL) is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent....A one-dimensional equivalent linear method (EQL) is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent. However, historical earthquake records and laboratory test results indicate that nonlinear soil behavior is frequency- dependent. Several frequency-dependent equivalent linear methods (FDEQL) related to the Fourier amplitude of shear strain time history have been developed to take into account the frequency-dependent soil behavior. Furthermore, the shear strain threshold plays an important role in soil behavior. For shear strains below the elastic shear strain threshold, soil behaves essentially as a linear elastic mate- rial. To consider the effect of elastic-shear-strain-threshold- and frequency-dependent soil behavior on wave propaga- tion, the shear-strain-threshold- and frequency-dependent equivalent linear method (TFDEQL) is proposed. A series of analyses is implemented for EQL, FDEQL, and TFDEQL methods. Results show that elastic-shear-strain-threshold- and frequency-dependent soil behavior plays a great influence on the computed site response, especially for the high- frequency band. Also, the effect of elastic-strain-threshold- and frequency-dependent soil behavior on the site response is analyzed from relatively weak to strong input motion, and results show that the effect is more pronounced as input motion goes from weak to strong.展开更多
The dynamic shear modulus ratio and damping ratio of sandy gravel are important parameters for the seismic response analysis of valley geomorphic sites,which have an important impact on the determination of design gro...The dynamic shear modulus ratio and damping ratio of sandy gravel are important parameters for the seismic response analysis of valley geomorphic sites,which have an important impact on the determination of design ground motion parameters. In this paper,the dynamic triaxial test of sandy gravels has been performed based on the project of the Shangluo Seismic Microzonation. Combined with the other results of sandy gravel,the recommended results of slightly dense,medium dense and dense sandy gravel were obtained. By building the typical site model,the influence of the dynamic shear modulus ratio and the damping ratio uncertainty on the seismic response of the site is studied. The results show that the uncertainty of the average of the dynamic shear modulus ratio and the damping ratio ± 1 times the standard deviation has little effect on the peak acceleration of the sandy gravel site,and the rationality of the grouping and statistical results is explained. Under different probability levels,the change in the shear modulus ratio and damping ratio leads to a significant difference in the high frequency response spectrum.The response spectrum of 0. 04-0. 1s ranges from about 20%,but it has little effect on the long period spectrum of more than 1. 0s. The study of dynamic shear modulus ratio and damping ratio of sandy gravel has the ability to improve the reliability of the designing ground motion parameters.展开更多
On the basis of the Xining active urban fault survey,we studied the relationship between the active urban fault and fold deformation.The result of this research shows that the Huangshuihe fault and the NW-striking fau...On the basis of the Xining active urban fault survey,we studied the relationship between the active urban fault and fold deformation.The result of this research shows that the Huangshuihe fault and the NW-striking fault on the northern bank of the Huangshuihe River are tensional faults on top of an anticline,the Nanchuanhe fault is a transverse tear fault resulting from differential folding on two sides of the fault,the east bank of the Beichuanhe River fault is a compressional fault developed on the core or climb of a syncline.By balance profile analysis of fold deformation and inversion of gravity anomaly data,we obtained the depth of the detachment plane and established the seismotectonic model of the Xining urban area.Based on the seismotectonic model,we analyzed the earthquake potential of the active urban fault.展开更多
River-dominated deltas are commonly developed at modern bays and lakes and ancient petroliferous basins.Water discharge is an important variable at pay zone scales in river-dominated delta reservoirs,which affects del...River-dominated deltas are commonly developed at modern bays and lakes and ancient petroliferous basins.Water discharge is an important variable at pay zone scales in river-dominated delta reservoirs,which affects deltaic sand distributions and evolutions.However,it's unclear how it influences riverdominated delta growth.This paper integrates Delft3 D simulations and modern analogs to analyze the effects of water discharge,considering growth time,sediment supply,and coupled effects of sediment properties.High water discharges lead to the formation of lobate deltas,and the water discharge of 1,000 m~3/s is a referenced threshold value.Fine-grained,highly-cohesive sediments increase the threshold values of water discharge at which the deltas become lobate from digitate,and vice versa.For the same simulation time,high water discharges favor more rugose shorelines,more distributary channels(especially secondary distributaries),and longer and wider deltas with more land areas.However,for the same sediment supply,high water discharges have few effects on shoreline roughness and the number of distributary channels.展开更多
The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the ...The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.展开更多
The data recorded during the site survey in the Zhangzhou area in Fujian Province between October 23, 2007 and December 3, 2007 was analyzed. The main methods adopted for the noise level of this area are the noise roo...The data recorded during the site survey in the Zhangzhou area in Fujian Province between October 23, 2007 and December 3, 2007 was analyzed. The main methods adopted for the noise level of this area are the noise root mean square( RMS),noise power spectrum density and noise coherency function. The results indicate that the noise levels of the survey sites are higher in the 1 s-10 s periods,which is the main frequency band of preliminary microseism,and also,two main noise sources were found in 1. 5 Hz and around 5 Hz. According to arithmetic,the direction and frequency band of the noise source were analyzed and academic proofs were presented. At last,we found that the noise source in 1. 5 Hz was made by the water wave aroused by the wind in the reservoir region and the noise source around 5 Hz was made by the power station in the northeast direction.展开更多
The explicit finite element analysis method combined with the artificial transmitting boundary theory is performed to evaluate the adjacent terrain effects on ground motion,and the influence of the distance between ad...The explicit finite element analysis method combined with the artificial transmitting boundary theory is performed to evaluate the adjacent terrain effects on ground motion,and the influence of the distance between adjacent terrains on the topographical amplification effects on ground motion is studied. The results show that:( 1) Compared to the case of a single hill,the presence of adjacent hills has little effect on the shape of the spectral ratio curve,but has a significant effect on the value of spectral ratio,which is dependent on the locations of observation points.( 2) The presence of adjacent hills has a greater effect on high-frequency ground motion,and with the increase of the distance between adjacent hills,such an effect weakens gradually,and the effect of the composite topography combined with multiple hills on ground motion gradually approaches that of a single hill.展开更多
基金Basic Research program from the Institute of Earthquake Forecasting, China Earthquake Administration(Grant No. 2021IEF0505, CEAIEF20220102, and CEAIEF2022050502)high-resolution seismic monitoring and emergency application demonstration (phase Ⅱ)(Grant No. 31-Y30F09-9001-20/22)+1 种基金the National Natural Science Foundation of China (Grant No. 42072248 and 42041006)the National Key Research and Development Program of China (Grant No. 2021YFC3000601-3 and 2019YFE0108900).
文摘Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits based on high-resolution satellite images.Therefore,we provide a framework for extracting liquefaction pits based on a case-based reasoning method.Furthermore,five covariates selection methods were used to filter the 11 covariates that were generated from high-resolution satellite images and digital elevation models(DEM).The proposed method was trained with 450 typical samples which were collected based on visual interpretation,then used the trained case-based reasoning method to identify the liquefaction pits in the whole study area.The performance of the proposed methods was evaluated from three aspects,the prediction accuracies of liquefaction pits based on the validation samples by kappa index,the comparison between the pre-and post-earthquake images,the rationality of spatial distribution of liquefaction pits.The final result shows the importance of covariates ranked by different methods could be different.However,the most important of covariates is consistent.When selecting five most important covariates,the value of kappa index could be about 96%.There also exist clear differences between the pre-and post-earthquake areas that were identified as liquefaction pits.The predicted spatial distribution of liquefaction is also consistent with the formation principle of liquefaction.
基金National Natural Science Foundation of China under Grant No.52278503。
文摘Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.
基金This research was financially supported by the Science and Technology Project of Yunnan Earthquake Administration(Grants No.2021YBZX17)the National Natural Science Foundation of China(Grants No.U2002211)+1 种基金the National Institute of Natural Hazards,Ministry of Emergency Management of China(Grants No.ZDJ 2019–21)the Yunnan Earthquake Disaster Risk Survey Project.
文摘An M_(S)6.4 earthquake occurred near Yangbi County, Dali Bai Autonomous Prefecture, Yunnan Province, at 21:48on May 21, 2021. The earthquake location is characterized by complex geological structures, with multiple active faults distributed around the epicenter that is located at the west edge of the Sichuan-Yunnan rhombic block(25.67°N, 99.87°E). A total of 42 ground cracks are found by earthquake field investigations. The cracks are mainly concentrated in the Ⅷ degree area on the west side of the Yangbi River. Among these, 9 coseismic tectonic ground cracks generated by shear fractures are found in three villages(i.e., Akechang, Meijia-Lijia, and Huajiazhuang), which are distributed along the strike of the northwest-trending linear folds, showing the tectonic characteristics of right-lateral tension or left-stepping cracks. The structural attribute of ground cracks sustains the kinematic properties of the Weixi-Qiaohou fault, namely right-lateral strike-slip.
基金supported by a subproject of the strategic leading science and technology project(A)of the Chinese Academy of Sciences(No.XDA20070302)we thank the reviewers and editors for their suggestions and opinions.
文摘According to volume 18(Xuanzong Ji Tang)of the historical book entitled the Old Book of Tang,the Hetao area of Inner Mongolia experienced a large earthquake in AD 849.However,previous work on that earthquake contains many discrepancies regarding its epicenter location,magnitude,deaths,and intensity.While exploring active faults in Baotou City,the present authors mapped the Daqing Mountain piedmont fault geologically.Based on previous work,several seismic deformation traces of more than 1000 years ago were found,and dating tests were conducted.The research showed the Daqing Mountain piedmont fault zone to be the seismogenic structure of the AD 849 earthquake.The length of earthquake surface rupture zone was around 80 km,and the macro epicenter was located in the active fault.The deformation center was located at 40.6°N,110.2°E.By collecting and analyzing more historical data about the AD 849 earthquake,reinterpreting some existing historical data,and re-examining the contradictory numbers of deaths in the historical data,the present analysis concludes that around 10,000 people were dead.It is suggested that this earthquake had a magnitude of 7½.According to the revised seismic parameters and the paleoearthquake recurrence period of the Daqing Mountain piedmont fault,the boundary of some potential seismic sources zone in the Baotou area are adjusted and the recurrence period of M8 and M7.5 are re-calculated.
基金sponsored by the Seismic Risk Assessment of Active Fault in Key Monitoring Prevention Area of China
文摘According to the results of estimation of the maximum potential earthquake in the project of "The Active Fault Detection and Seismic Risk Evaluation( Phase II) of Zhengzhou City",the near east-west trending Laoyachen fault and Shangjie fault are developed in the urban area.The Laoyachen fault was not active in the Quaternary,but the Shangjie fault may have the potential of generating M5.0~5.5 earthquakes.In order to get the probability of occurrence of maximum potential earthquakes,we delineate the statistical areas and the potential source areas and calculate the seismicity parameters and the space distribution functions.Our study shows that the probability of occurrence of an earthquake with M≥5.0 on the faults in Zhengzhou city is 6% in the next 50 years and 11% in the next 100years.
基金sponsored by the Science and Technology Development Program of Ministry of Railways,PRC(2008G027-B)Special Program of Deep Exploration Techniques and Experimental Studies of Ministry of Land and Resources,PRC(Sinoprobe-06-04)
文摘According to field investigation and interpretation of remote sensing images,the north segment of the Longling-Ruili fault is a Holocene dextral strike-slip fault with a small amount of normal faulting.Based on large-scale geological mapping at some typical locations and quantitative geomorphologic deformation measurement and dating analysis,this fault is a Holocene active fault.The strike-slip rate of the Longling-Ruili fault is 2.2 ~2.5mm / a and vertical slip rate is 0.6mm /a since the late Pleistocene epoch.The strike-slip rate of the Longling-Ruili fault is 1.8~3.0mm /a and vertical slip rate is 0.5mm /a since the Holocene epoch.Based on the Poisson model,lognormal model and BPT model,the occurrence probability of strong earthquakes in 50 years is estimated to be 6.32%,0.08%and 0.05%,respectively.Then,a 1.82% probability of occurrence of characteristic earthquake for the north segment of the Longling-Ruili fault is obtained by setting a weight of 0.28,0.36 and 0.36 to the Poisson model,lognormal model and BPT model,respectively.
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supported by special R&D project in earthquake science,Seismic risk assessment of active faults in the national key earthquake monitoring and prevention regions(20070851)
文摘The coseismic surface rupture zone of the seismogenic fault of the MS7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°~320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9km long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.
基金sponsored by the Special Earthquake Research Program(20070851)National Key Basic Research Development Planning grogram(2004CB418401)+1 种基金Basic Science Research Professional of Institute of Crustal Dynamics (2008)National Science and Technology Support Program(2006BAC13B01 -0202),China
文摘The M8.0 Wenchuan earthquake occurred on the Longmenshan fault zone. Based on field investigation of the surface rupture and focal mechanism study of the aftershocks, we discuss the geological relationship of the main, secondary and triggered ruptures. The main rupture is about 200km long and can be divided into the south part and the north part. The south part consists of two parallel fault zones characterized by reverse faulting, with several parallel secondary ruptures on the hanging wall of the main fault, and the north part is a single main fault zone characterized by lateral strike-slip and reverse faulting. Compared to a 300km long aftershock distribution, the surface rupture only occupies 200km, and the remaining 100km on the northeast of the main rupture was triggered by aftershocks. Study on the ruptures of this earthquake will be useful for studying the earthquake risk evolution on the Longmenshan fault system.
基金financially supported by the Yuguang Basin 1:50000 Geological Mapping Project (no. 201210916),a subsubject of Active Fault Seismic Hazard Assessment Project of China's Key Area for Surveillance and Protection
文摘Based on high-resolution remote sensing image interpretation, digital elevation model 3-D analysis, field geologic field investigation, trenching engineering, and ground-penetrating radar, synthetic research on the evolution of the Yuguang Basin South Margin Fault (YBSMF) in northwest Beijing was carried out. We found that the propagation and growth of faults most often occurred often at two locations: the fault overlapping zone and the uneven or rough fault segment. Through detailed observation and analysis of all cropouts of faults along the YBSMF from zone a to zone i, we identified three major factors that dominate or affect fault propagation and growth. First, the irregularity of fault geometry determine the propagation and growth of the fault, and therefore, the faults always propagate and grow at such irregular fault segments. The fault finally cuts off and eliminates its irregularity, making the fault geometry and fault plane smoother than before, which contributes to the slipping movement of the half-graben block in the basin. Second, the scale of the irregularity of the fault geometry affects the result of fault propagation and growth, that is, the degree of the cutting off of fault irregularity. The degree of cutting off decreases as irregularity scale increases. Third, the maximum possible slip displacement of the fault segment influences the duration of fault propagation and growth. The duration at the central segments with a large slip displacement is longer than that at the end segments with a smaller slippage value.
基金National Natural Science Foundation of China under Grant Nos.51978334 and 51978335。
文摘This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,China.Emphasis is placed on the major factors for predominating the dynamic shear modulus(G)and damping ratio(λ)in the shear strain amplitude(γ_(a))from 10^(-5) to 10^(-2),involving depth,sedimentary facies types,and water content of marine soils.The empirical equations of the small-strain shear modulus(G_(max))and damping ratio(λ_(min))using a single-variable of depth H are established for the three marine soils.A remarkable finding is that the curves of shear modulus reduction(G/G_(max))and the damping ratio(λ)with increasing γ_(a) of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content W.This finding is validated by independent experimental data from the literature.At the similar depths,the G value of the marine soils of terrestrial facies is the largest,followed b_(y) the neritic facies,and the G value of the marine soils of abyssal facies is the smallest.The sedimentary facies types of the marine soils have slight effect on theλvalue.Another significant finding is that the shear modulus reduction curves plotted against the γ_(a) of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils,while the damping curves plotted against γ_(a) are just the opposite.The results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data.
基金Project(2011CB013601) supported by the National Basic Research Program of ChinaProject(51378258) supported by the National Natural Science Foundation of China
文摘Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear analytical model for Fuzhou Basin was established.The peak ground motion acceleration(PGA) and focusing effect with depth were analyzed.Meanwhile,the results by wave propagation of one-dimensional(1D) layered medium equivalent linearization method were added for contrast.The results show that:1) PGA at different depths are obviously amplified compared to the input ground motion,amplification effect of both funnel-shaped depression and upheaval areas(based on the shape of bedrock surface) present especially remarkable.The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers,while the 1D results turn out that the PGA decreases with depth,except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas,PGA amplification effect above 8 m depth shows relatively larger,to the upheaval areas,PGA amplification effect from 15 m to 25 m depth seems more significant.However,the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.
基金supported by the National Natural Science Foundation of China under grant No.50608066Chinese Earthquake Science Foundation under grant No.A07045
文摘By expressing the wave functions in the form of Fourier-Bessel series, the analytical solution for the two-dimension scattering problem of plane P waves by the cylindrical canyon topography that contains arbitrary number of circular-arc-shaped layers is presented firstly. And then, the convergence of the proposed series solution with the truncation number of terms is discussed, which demonstrates that the analytical solution can converge even for very high frequencies of the incident P wave. Finally, using this solution, the influences that are imposed on the stationary ground motion by the number and the sequence of alluvial layers, as well as the stiffness of soft interlayer contained in the canyon, are studied,
基金supported by the Science for Earthquake Resilience of China Earthquake Administration(Grant No.XH14060)the National Natural Science Foundation of China(Grant No.51478135)
文摘A one-dimensional equivalent linear method (EQL) is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent. However, historical earthquake records and laboratory test results indicate that nonlinear soil behavior is frequency- dependent. Several frequency-dependent equivalent linear methods (FDEQL) related to the Fourier amplitude of shear strain time history have been developed to take into account the frequency-dependent soil behavior. Furthermore, the shear strain threshold plays an important role in soil behavior. For shear strains below the elastic shear strain threshold, soil behaves essentially as a linear elastic mate- rial. To consider the effect of elastic-shear-strain-threshold- and frequency-dependent soil behavior on wave propaga- tion, the shear-strain-threshold- and frequency-dependent equivalent linear method (TFDEQL) is proposed. A series of analyses is implemented for EQL, FDEQL, and TFDEQL methods. Results show that elastic-shear-strain-threshold- and frequency-dependent soil behavior plays a great influence on the computed site response, especially for the high- frequency band. Also, the effect of elastic-strain-threshold- and frequency-dependent soil behavior on the site response is analyzed from relatively weak to strong input motion, and results show that the effect is more pronounced as input motion goes from weak to strong.
基金sponsored by the Earthquake Disaster Prevention and ReductionProgram for the 12th “Five-year Plan” of Shaanxi Province(SCZC2012-TP-905/1)
文摘The dynamic shear modulus ratio and damping ratio of sandy gravel are important parameters for the seismic response analysis of valley geomorphic sites,which have an important impact on the determination of design ground motion parameters. In this paper,the dynamic triaxial test of sandy gravels has been performed based on the project of the Shangluo Seismic Microzonation. Combined with the other results of sandy gravel,the recommended results of slightly dense,medium dense and dense sandy gravel were obtained. By building the typical site model,the influence of the dynamic shear modulus ratio and the damping ratio uncertainty on the seismic response of the site is studied. The results show that the uncertainty of the average of the dynamic shear modulus ratio and the damping ratio ± 1 times the standard deviation has little effect on the peak acceleration of the sandy gravel site,and the rationality of the grouping and statistical results is explained. Under different probability levels,the change in the shear modulus ratio and damping ratio leads to a significant difference in the high frequency response spectrum.The response spectrum of 0. 04-0. 1s ranges from about 20%,but it has little effect on the long period spectrum of more than 1. 0s. The study of dynamic shear modulus ratio and damping ratio of sandy gravel has the ability to improve the reliability of the designing ground motion parameters.
基金This project was sponsored by National Development and Reform Commission (NDRC) on studies of experimental exploration of active fault in urban area(20041138)
文摘On the basis of the Xining active urban fault survey,we studied the relationship between the active urban fault and fold deformation.The result of this research shows that the Huangshuihe fault and the NW-striking fault on the northern bank of the Huangshuihe River are tensional faults on top of an anticline,the Nanchuanhe fault is a transverse tear fault resulting from differential folding on two sides of the fault,the east bank of the Beichuanhe River fault is a compressional fault developed on the core or climb of a syncline.By balance profile analysis of fold deformation and inversion of gravity anomaly data,we obtained the depth of the detachment plane and established the seismotectonic model of the Xining urban area.Based on the seismotectonic model,we analyzed the earthquake potential of the active urban fault.
基金financially supported by the National Natural Science Foundation of China(No.41772101)China Scholarship Council。
文摘River-dominated deltas are commonly developed at modern bays and lakes and ancient petroliferous basins.Water discharge is an important variable at pay zone scales in river-dominated delta reservoirs,which affects deltaic sand distributions and evolutions.However,it's unclear how it influences riverdominated delta growth.This paper integrates Delft3 D simulations and modern analogs to analyze the effects of water discharge,considering growth time,sediment supply,and coupled effects of sediment properties.High water discharges lead to the formation of lobate deltas,and the water discharge of 1,000 m~3/s is a referenced threshold value.Fine-grained,highly-cohesive sediments increase the threshold values of water discharge at which the deltas become lobate from digitate,and vice versa.For the same simulation time,high water discharges favor more rugose shorelines,more distributary channels(especially secondary distributaries),and longer and wider deltas with more land areas.However,for the same sediment supply,high water discharges have few effects on shoreline roughness and the number of distributary channels.
基金sponsored by Active Faults Seismic Hazard Assessment in Key Earthquake Monitoring and Defensive Region of China
文摘The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.
基金sponsored by the Earthquake Monitoring System Operational Program of Department of Earthquake Monitoring and Prediction,CEA,in 2016(2200404)
文摘The data recorded during the site survey in the Zhangzhou area in Fujian Province between October 23, 2007 and December 3, 2007 was analyzed. The main methods adopted for the noise level of this area are the noise root mean square( RMS),noise power spectrum density and noise coherency function. The results indicate that the noise levels of the survey sites are higher in the 1 s-10 s periods,which is the main frequency band of preliminary microseism,and also,two main noise sources were found in 1. 5 Hz and around 5 Hz. According to arithmetic,the direction and frequency band of the noise source were analyzed and academic proofs were presented. At last,we found that the noise source in 1. 5 Hz was made by the water wave aroused by the wind in the reservoir region and the noise source around 5 Hz was made by the power station in the northeast direction.
基金sponsored by the China National Special Fund for Earthquake Scientific Research in Public Interest(Grant No.201408002)Earthquake Science and Technology Spark Plan of China Earthquake Administration(XH14061Y)
文摘The explicit finite element analysis method combined with the artificial transmitting boundary theory is performed to evaluate the adjacent terrain effects on ground motion,and the influence of the distance between adjacent terrains on the topographical amplification effects on ground motion is studied. The results show that:( 1) Compared to the case of a single hill,the presence of adjacent hills has little effect on the shape of the spectral ratio curve,but has a significant effect on the value of spectral ratio,which is dependent on the locations of observation points.( 2) The presence of adjacent hills has a greater effect on high-frequency ground motion,and with the increase of the distance between adjacent hills,such an effect weakens gradually,and the effect of the composite topography combined with multiple hills on ground motion gradually approaches that of a single hill.