In this study,the shear-wave splitting parameters of local seismic events from the source regions of the 2023 Türkiye MW7.7 and MW7.6 doublet earthquakes(event 1 and event 2,respectively)were measured from June 1...In this study,the shear-wave splitting parameters of local seismic events from the source regions of the 2023 Türkiye MW7.7 and MW7.6 doublet earthquakes(event 1 and event 2,respectively)were measured from June 1,2022,to April 25,2023,and their spatiotemporal characteristics were analyzed.The results revealed clear spatial and temporal differences.Spatially,the dominant fast-wave polarization direction at each station shows a strong correlation with the direction of the maximum horizontal principal compressive stress,as characterized by focal mechanism solutions of seismic events(MW≥3.5)near the station.The dominant fast-wave polarization direction and the regional stress field also showed a strong correlation with the intermovement of the Arabian Plate,African Plate,and Anatolian Block.Along the Nurdagi-Pazarcik fault zone,the seismic fault of event 1,stations closer to the middle of the fault where the mainshock occurred exhibited notably greater delay times than stations located towards the ends of the fault and far from the mainshock.In addition,the stations located to the east of the Nurdagi-Pazarcik fault and to the north of the Sürgüfault also exhibited large delay times.The spatial distribution of shear-wave splitting parameters obtained from each station indicates that the upper-crust anisotropy in the source area is mainly controlled by the regional stress field,which is closely related to the state of the block motion.During the seismogenic process of the MW7.7 earthquake,more stress accumulated in the middle of the Nurdagi-Pazarcik fault than at either end of the fault.Under the influence of the MW7.7 and MW7.6 events,the stress that accumulated during the seismogenic process of the earthquake doublet may have migrated towards some areas outside the aftershock intensive area after the earthquakes,and the crustal stress and its adjustment range near the outer stations increased significantly.With the exception of two stations with few effective events,all stations showed a consistent change in shear-wave splitting parameters over time.In particular,each station showed a decreasing trend in delay times after the doublet earthquakes,reflecting the obvious intensification of crustal stress adjustment in the seismogenic zone after the doublet earthquakes.With the occurrence of the earthquake doublet and a large number of aftershocks,the stress accumulated during the seismogenic process of the doublet earthquakes is gradually released,and then the adjustment range of crustal stress is also gradually reduced.展开更多
Based on the dual source cumulative rotation technique in the time-domain proposed by Zeng and MacBeth（1993）,a new algebraic processing technique for extracting shear-wave splitting parameters from multi-component V...Based on the dual source cumulative rotation technique in the time-domain proposed by Zeng and MacBeth（1993）,a new algebraic processing technique for extracting shear-wave splitting parameters from multi-component VSP data in frequency-dependent medium has been developed.By using this dual source cumulative rotation technique in the frequency-domain（DCTF）,anisotropic parameters,including polarization direction of the shear-waves and timedelay between the fast and slow shear-waves,can be estimated for each frequency component in the frequency domain.It avoids the possible error which comes from using a narrow-band filter in the current commonly used method.By using synthetic seismograms,the feasibility and validity of the technique was tested and a comparison with the currently used method was also given.The results demonstrate that the shear-wave splitting parameters frequency dependence can be extracted directly from four-component seismic data using the DCTF.In the presence of larger scale fractures,substantial frequency dependence would be found in the seismic frequency range,which implies that dispersion would occur at seismic frequencies.Our study shows that shear-wave anisotropy decreases as frequency increases.展开更多
When propagating through anisotropic rocks in the crust, shear-waves split into faster and slower components with almost orthogonal polarizations. For nearly vertical propagation the polarization of fast shear- wave ...When propagating through anisotropic rocks in the crust, shear-waves split into faster and slower components with almost orthogonal polarizations. For nearly vertical propagation the polarization of fast shear- wave （PFS） is parallel to both the strike of the cracks and the direction of maximum horizontal stress, therefore it is possible to use PFS to study stress in the crust. This study discusses several examples in which PFS is applied to deduce the compressive stress in North China, Longmenshan fault zone of east edge of Tibetan plateau and Yunnan zone of southeast edge of Tibetan plateau, also discusses temporal variations of PFS orientations of 1999 Xiuyan earthquake sequences of northeastern China. The results are consistent to those of other independent traditional stress measurements. There is a bridge between crustal PFS and the crustal principal compressive stress although there are many unclear disturbance sources. This study suggests the PFS results could be used to deduce regional and in situ principal compressive stress in the crust only if there are enough seismic stations and enough data. At least, PFS is a useful choice in the zone where there are a large number of dense seismic stations.展开更多
In 2001 three earthquakes occurred in Shidian in Yunnan Province, which were the MS=5.2 on April 10, the MS=5.9 on April 12 and the MS=5.3 on June 8. Based on the data from the station Baoshan of Yunnan Telemetry Digi...In 2001 three earthquakes occurred in Shidian in Yunnan Province, which were the MS=5.2 on April 10, the MS=5.9 on April 12 and the MS=5.3 on June 8. Based on the data from the station Baoshan of Yunnan Telemetry Digital Seismograph Network, the variational characteristics of shear-wave splitting on these series of strong earthquakes has been studied by using the systematic analysis method (SAM) of shear-wave splitting. The result shows the time delays of shear-wave splitting basically increase with earthquake activity intensifying. However the time delays abruptly decrease immediately before strong aftershocks. It accords with the stress relaxation before earthquakes, which was found recently in study on shear-wave splitting. The result suggests it is significant for reducing the harm degree of earthquakes to develop the stress-forecasting on earthquake in strong active tectonic zones and economic developed regions or big cities under the danger of strong earthquakes.展开更多
A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaoj...A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.展开更多
In order to make a more effective use of the data from regional digital seismograph networks and to promote the study on shear wave splitting and its application to earthquake stress-forecasting, SAM software system, ...In order to make a more effective use of the data from regional digital seismograph networks and to promote the study on shear wave splitting and its application to earthquake stress-forecasting, SAM software system, i.e., the software on systematic analysis method of shear wave splitting has been developed. This paper introduces the design aims, system structure, function and characteristics about the SAM software system and shows some graphical interfaces of data input and result output. Lastly, it discusses preliminarily the study of shear wave splitting and its application to earthquake forecasting.展开更多
Using seismic waveform data recorded at station YK (Yingkou) of Liaoning Telemetry Digital Seismic Network, this paper studied the characteristics of shear-wave splitting before and after the Xiuyan MS5.9 (ML5.3) eart...Using seismic waveform data recorded at station YK (Yingkou) of Liaoning Telemetry Digital Seismic Network, this paper studied the characteristics of shear-wave splitting before and after the Xiuyan MS5.9 (ML5.3) earthquake in November 29, 1999 with SAM method. The results show that the predominant polarizations of fast shear-waves at YK is in direction of ENE-WSW, consistent with the direction of regional principal compressive stress and also consistent with the direction of the regional tectonic stress field in North China; time-delays increasing before Xiuyan earthquake may shows accumulation of stress before earthquake. The predominant polarizations of fast shear-waves at YK are also related to the spatial distribution of small earthquakes and correlate with the fault strike. The histogram of monthly average polarizations of fast shear-waves shows that polarizations of fast shear-waves also seems to change from two months before the earthquake, but it still needs more data for verification.展开更多
In 2001 three earthquakes occurred in Shidian in Yunnan Province, which were the MS=5.2 on April 10, the MS=5.9 on April 12 and the MS=5.3 on June 8. Based on the data from the station Baoshan of Yunnan Telemetry Digi...In 2001 three earthquakes occurred in Shidian in Yunnan Province, which were the MS=5.2 on April 10, the MS=5.9 on April 12 and the MS=5.3 on June 8. Based on the data from the station Baoshan of Yunnan Telemetry Digital Seismograph Network, the variational characteristics of shear-wave splitting on these series of strong earthquakes has been studied by using the systematic analysis method (SAM) of shear-wave splitting. The result shows the time delays of shear-wave splitting basically increase with earthquake activity intensifying. However the time delays abruptly decrease immediately before strong aftershocks. It accords with the stress relaxation before earthquakes, which was found recently in study on shear-wave splitting. The result suggests it is significant for reducing the harm degree of earthquakes to develop the stress-forecasting on earthquake in strong active tectonic zones and economic developed regions or big cities under the danger of strong earthquakes.展开更多
Seismic anisotropy and its main features along the convergent boundary between Africa and Iberia are detected through the analysis of teleseismic shear-wave splitting. Waveform data generated by 95 teleseismic events ...Seismic anisotropy and its main features along the convergent boundary between Africa and Iberia are detected through the analysis of teleseismic shear-wave splitting. Waveform data generated by 95 teleseismic events recorded at 17 broadband stations deployed in the western Mediterranean region are used in the present study. Although the station coverage is not uniform in the Iberian Peninsula and north- west Africa, significant variations in the fast polarization directions and delay times are observed at stations located at different tectonic domains. Fast polarization directions are oriented predominantly NW-SE at most stations which are close to the plate boundary and in central Iberia; being consistent with the absolute plate motion in the region. In the northern part of the Iberian Peninsula, fast velocity direc- tions are oriented nearly E--W; coincident with previous results. Few stations located slightly north of the plate boundary and to the southeast of lberia show E--W to NE-SW fast velocity directions, which may be related to the Alpine Orogeny and the extension direction in lberia. Delay times vary significantly between 0.2 and 1.9 s for individual measurements, reflecting a highly anisotropic structure beneath the recording stations. The relative motion between Africa and lberia represents the main reason for the observed NW-SE orientations of the fast velocity directions. However, different causes of anisotropy have also to be considered to explain the wide range of the splitting pattern observed in the western Mediterranean region. Many geophysical observations such as the low Pn velocity, lower lithospheric Q values, higher heat flow and the presence of high conductive features support the mantle flow in the western Mediterranean, which may contribute and even modify the splitting pattern beneath the studied region.展开更多
Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of pol...Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.展开更多
The temporal evolution of shear-wave splitting and geoelectrical anisotropy of earth media during the preparation and occurrence of the Yongdeng MS5.8 earthquake is studied based on the digital seismic data and contin...The temporal evolution of shear-wave splitting and geoelectrical anisotropy of earth media during the preparation and occurrence of the Yongdeng MS5.8 earthquake is studied based on the digital seismic data and continuous magnetotelluric (MT) records. The results show that the direction of polarization of the fast S-wave gradually rotated from north by east to north by west before the Yongdeng earthquake and returned to north by east after the earthquake. Moreover, the time delay between the fast S wave and slow S wave increased to the largest until the earthquake occurred. On the other hand, the directions of geoelectrical principal axes also changed before earthquake, and exhibited identical characteristics in the frequency domain. The direction of the axis (pxy), which was originally perpendicular to the fault near station, varied from N17°to N15°before earthquake, and returned to north by east after the earthquake. Correspondingly, the change of pxy was most obvious in the period range of 160 s to 226 s, but the variation of pyx was less obvious. The focal mechanism solution of the earthquake showed that the direction of P-axis was N15°. Conclusions are: (1) The fast S-wave polarization, one of the geoelectrical principal axes and the P-axis were in agreement in orientation during earthquake preparation, which is the result of the alignment of EDA cracks; (2) The fact that the geoelectrical axes identically varied with frequency demonstrated that EDA is really widespread in the crust; (3) The variation of MT apparent resistivity also showed the existence of anisotropy and has its own features: The static anisotropy of resistivity is controlled by the tectonic conditions of the station, while the dynamic anisotropy is caused and affected by the seismic stress field; The resistivity along the axis parallel to the P-axis showed the most obvious variation, while the difference in variation with frequency shows that the variation of resistivity depends not only on direction but also on buried depth.展开更多
Earthquakes of M_S5. 6 and M_S6.1 occurred in Yingjiang,Yunnan on May 24 and May 30,2014 respectively. In this paper,we use the waveform data recorded by mobile seismic stations( KAC) which were set up in the source a...Earthquakes of M_S5. 6 and M_S6.1 occurred in Yingjiang,Yunnan on May 24 and May 30,2014 respectively. In this paper,we use the waveform data recorded by mobile seismic stations( KAC) which were set up in the source area after the Yingjiang MS5. 6earthquake on May 24,2014 to study the shear-wave splitting characteristics of Yingjiang M_S6.1 earthquake sequence with the SAM method. The result shows that predominant polarization of fast shear-waves before the M_S6.1 earthquake is consistent with the direction of regional principal compressive stress,and predominant polarization of fast shear-waves before the M_S6.1 earthquake show better consistency and smaller dispersion compared to after the M_S6.1 earthquake,and there may be a deflection for the fast shearwaves predominant polarization between the M_S6.1 earthquake sequence and foreshock sequence. We found that the time-delays generally exhibited a lower level before the M_S6.1earthquake and a relatively higher value after the M_S6.1 earthquake.展开更多
This paper mainly observed and analyzed the character of shear-wave splitting in rock specimens while they were in the critical state of rupture. The rock specimens for study are made of Laizhou marble from Shandong, ...This paper mainly observed and analyzed the character of shear-wave splitting in rock specimens while they were in the critical state of rupture. The rock specimens for study are made of Laizhou marble from Shandong, China. A series of records were obtained from two rock specimens when they were in the critical state of rupture. The result shows that, in the critical state just before rock rupture, there may be the phenomenon of rise and fall in the time delay of shear-wave splitting, even though the load was kept constant. That is to say, the time delay of shear-wave splitting may have a falling process before rock rupture.展开更多
The upper crustal anisotropy of Yunnan area, SE margin of Tibetan Plateau, is investigated by measuring the shear wave splitting of local earthquakes. The mean value of the measured delay times is 0.054 s and far less...The upper crustal anisotropy of Yunnan area, SE margin of Tibetan Plateau, is investigated by measuring the shear wave splitting of local earthquakes. The mean value of the measured delay times is 0.054 s and far less than that from Pms splitting analysis, indicating that the crustal anisotropy is contributed mostly from mid-lower crust. The fast polarization directions are mostly sub-parallel to the maximum horizontal compression directions while the stations near fault zones show fault-parallel fast polarization directions, suggesting both stress and geological structure contribute to the upper crust anisotropy.Comparing fast polarization directions from shear wave splitting of local earthquakes and Pms, large angle differences are shown at most stations, implying different anisotropy properties between upper and mid-lower crust. However, in southwestern Yunnan, the fast polarization directions of Pms and Swave splitting are nearly parallel, and the stress and surface strain rate directions show strong correlation, which may indicate that the surface and deep crust deformations can be explained by the same mechanism and the surface deformation can represent the deformation of the whole crust. Therefore,the high correlation between surface strain and mantle deformation in this area suggests the mechanical coupling between crust and mantle in southwestern Yunnan. In the rest region of Yunnan, the crustmantle coupling mechanisms are supported by the lack of significant crustal anisotropy with Ne S fast polarization directions from Pms splitting. Therefore, we conclude that the crust and upper mantle are coupled in Yunnan, SE margin of Tibetan Plateau.展开更多
This paper briefly discusses the new methods that the authors have put forward to distinguish splitting shear-waves.By combining these new methods with other methods,the authors have processed the recorded data of an ...This paper briefly discusses the new methods that the authors have put forward to distinguish splitting shear-waves.By combining these new methods with other methods,the authors have processed the recorded data of an earthquake.The study results are consistent with each other.展开更多
Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area....Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area. The result shows that the time delays of slow shear waves of the DJS station, which is not far from the epicenter and where the distribution of faults is complex near the station, are relatively larger and the polarization directions of fast shear waves are not concentrated; the predominant polarization direction of fast shear waves of WUJ station, with single fault distributed nearby, has a difference of 35° to the strike of the fault and is inconsistent with the direction of regional principal compressive stress. The predominant polarization direction of fast shear waves of SZD station with no faults nearby is in accordance with regional principal compressive stress. There is no obvious regular relationshipship between the delay time and the focal depth.展开更多
Direct seawater splitting has emerged as a popular and promising research direction for synthesising clean,green,non-polluting,and sustainable hydrogen energy without depending on high-purity water in the face of the ...Direct seawater splitting has emerged as a popular and promising research direction for synthesising clean,green,non-polluting,and sustainable hydrogen energy without depending on high-purity water in the face of the world’s shortage of fossil energy.However,efficient seawater splitting is hindered by slow kinetics caused by the ultra-low conductivity and the presence of bacteria,microorganisms,and stray ions in seawater.Additionally,producing hydrogen on an industrial scale is challenging due to the high production cost.The present review addresses these challenges from the catalyst point of view,namely,that designing catalysts with high catalytic activity and stability can directly affect the rate and effect of seawater splitting.From the ion transfer perspective,designing membranes can block harmful ions,improving the stability of seawater splitting.From the energy point of view,mixed seawater systems and self-powered systems also provide new and low-energy research systems for seawater splitting.Finally,ideas and directions for further research on direct seawater splitting in the future are pointed out,with the aim of achieving low-cost and high-efficiency hydrogen production.展开更多
Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by ...Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by single-atom catalysts(SACs),which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports.Recently,bimetallic SACs(bimSACs)have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports.BimSACs offer an avenue for rich metal–metal and metal–support cooperativity,potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges,substrate activation with reversible redox cycles,simultaneous multi-electron transfer,regulation of spin states,tuning of electronic properties,and cyclic transition states with low activation energies.This review aims to encapsulate the growing advancements in bimSACs,with an emphasis on their pivotal role in hydrogen generation via water splitting.We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs,elucidate their electronic properties,and discuss their local coordination environment.Overall,we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction,the two half-reactions of the water electrolysis process.展开更多
Recent advancements in electrocatalysis have highlighted the exceptional application value of amorphous electrocatalysts. Withtheir unique atomic configurations, these electrocatalysts exhibit superior catalytic perfo...Recent advancements in electrocatalysis have highlighted the exceptional application value of amorphous electrocatalysts. Withtheir unique atomic configurations, these electrocatalysts exhibit superior catalytic performance compared to that of their crystalline coun-terparts. Transition metal(TM) amorphous ribbon-shaped electrocatalysts have recently emerged as a new frontier in the catalysis field.Dealloying is widely considered a fascinating method for enhancing the electrocatalyst performance. In this review, we comprehensivelyexamine the principles of water electrolysis, discuss the prevalent methods for fabricating ribbon-configured electrocatalysts, and providean overview of amorphous alloys. Furthermore, we discuss binary, ternary, and high-entropy amorphous TM-based electrocatalysts,which satisfy the requirements necessary for effective water electrolysis. We also propose strategies to enhance the activity of amorphousTM-based ribbons, including morphology control, defect engineering, composition optimization, and heterostructure creation in differentelectrolytes. Our focus extends to the latest developments in the design of heterogeneous micro/nanostructures, management of prepara-tion techniques, and synthesis of different compositions. Finally, we address the ongoing challenges and provide a perspective on the fu-ture development of broadly applicable, self-supporting TM ribbon-shaped electrocatalysts.展开更多
Professor Kazunari Domen at the Shinshu University and the University of Tokyo has pioneered materials and techniques for solar-driven water splitting using photocatalysts,a promising technology for contributing to th...Professor Kazunari Domen at the Shinshu University and the University of Tokyo has pioneered materials and techniques for solar-driven water splitting using photocatalysts,a promising technology for contributing to the construction of a sustainable and carbon-neutral society.In this paper,we summarize his groundbreaking contributions to photocatalytic water splitting and,more broadly,photocatalytic research.We highlight various novel functional photocatalytic materials,including oxides,(oxy)nitrides,and oxysulfides,along with innovative techniques such as cocatalyst engineering and Z-scheme system construction developed by the Domen Group.His team has also pioneered readily accessible and cost-effective photo(electro)chemical device fabrication methods,such as the particle-transfer method and thin-film-transfer method.Furthermore,their research has made significant contributions to understanding the(photo)catalytic mechanisms using advanced characterization techniques.Together with his research team,Professor Domen has set many milestones in the field of photocatalytic overall water splitting,notably demonstrating the first scalable and stable 100 m^(2)solar H_(2)production system using only water and sunlight.His work has revealed the potential for practical solar H2 production from water and sunlight,and highlighted the application of fundamental principles,combined with chemical and materials science tools,to design effective photocatalytic systems.Through this review,we focus on his research and the foundational design principles that can inspire the development of efficient photocatalytic systems for water splitting and solar fuel production.By building on his contributions,we anticipate a significant impact on addressing major global energy challenges.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42074053 and 42374079)the Fundamental Research Funds from the Institute of Geophysics,China Earthquake Administration(Nos.DQJB19B30 and JY2022Z02).
文摘In this study,the shear-wave splitting parameters of local seismic events from the source regions of the 2023 Türkiye MW7.7 and MW7.6 doublet earthquakes(event 1 and event 2,respectively)were measured from June 1,2022,to April 25,2023,and their spatiotemporal characteristics were analyzed.The results revealed clear spatial and temporal differences.Spatially,the dominant fast-wave polarization direction at each station shows a strong correlation with the direction of the maximum horizontal principal compressive stress,as characterized by focal mechanism solutions of seismic events(MW≥3.5)near the station.The dominant fast-wave polarization direction and the regional stress field also showed a strong correlation with the intermovement of the Arabian Plate,African Plate,and Anatolian Block.Along the Nurdagi-Pazarcik fault zone,the seismic fault of event 1,stations closer to the middle of the fault where the mainshock occurred exhibited notably greater delay times than stations located towards the ends of the fault and far from the mainshock.In addition,the stations located to the east of the Nurdagi-Pazarcik fault and to the north of the Sürgüfault also exhibited large delay times.The spatial distribution of shear-wave splitting parameters obtained from each station indicates that the upper-crust anisotropy in the source area is mainly controlled by the regional stress field,which is closely related to the state of the block motion.During the seismogenic process of the MW7.7 earthquake,more stress accumulated in the middle of the Nurdagi-Pazarcik fault than at either end of the fault.Under the influence of the MW7.7 and MW7.6 events,the stress that accumulated during the seismogenic process of the earthquake doublet may have migrated towards some areas outside the aftershock intensive area after the earthquakes,and the crustal stress and its adjustment range near the outer stations increased significantly.With the exception of two stations with few effective events,all stations showed a consistent change in shear-wave splitting parameters over time.In particular,each station showed a decreasing trend in delay times after the doublet earthquakes,reflecting the obvious intensification of crustal stress adjustment in the seismogenic zone after the doublet earthquakes.With the occurrence of the earthquake doublet and a large number of aftershocks,the stress accumulated during the seismogenic process of the doublet earthquakes is gradually released,and then the adjustment range of crustal stress is also gradually reduced.
基金supported by the National Natural Science Foundation of China (No. 41004055)
文摘Based on the dual source cumulative rotation technique in the time-domain proposed by Zeng and MacBeth（1993）,a new algebraic processing technique for extracting shear-wave splitting parameters from multi-component VSP data in frequency-dependent medium has been developed.By using this dual source cumulative rotation technique in the frequency-domain（DCTF）,anisotropic parameters,including polarization direction of the shear-waves and timedelay between the fast and slow shear-waves,can be estimated for each frequency component in the frequency domain.It avoids the possible error which comes from using a narrow-band filter in the current commonly used method.By using synthetic seismograms,the feasibility and validity of the technique was tested and a comparison with the currently used method was also given.The results demonstrate that the shear-wave splitting parameters frequency dependence can be extracted directly from four-component seismic data using the DCTF.In the presence of larger scale fractures,substantial frequency dependence would be found in the seismic frequency range,which implies that dispersion would occur at seismic frequencies.Our study shows that shear-wave anisotropy decreases as frequency increases.
基金supported by International Science and Technology Cooperation Program of China(2010DFB20190)National Natural Science Foundation of China(41040034 and 41174042)the support by basic research project of Institute of Earthquake Science,China Earthquake Administration(2009IES0211)
文摘When propagating through anisotropic rocks in the crust, shear-waves split into faster and slower components with almost orthogonal polarizations. For nearly vertical propagation the polarization of fast shear- wave （PFS） is parallel to both the strike of the cracks and the direction of maximum horizontal stress, therefore it is possible to use PFS to study stress in the crust. This study discusses several examples in which PFS is applied to deduce the compressive stress in North China, Longmenshan fault zone of east edge of Tibetan plateau and Yunnan zone of southeast edge of Tibetan plateau, also discusses temporal variations of PFS orientations of 1999 Xiuyan earthquake sequences of northeastern China. The results are consistent to those of other independent traditional stress measurements. There is a bridge between crustal PFS and the crustal principal compressive stress although there are many unclear disturbance sources. This study suggests the PFS results could be used to deduce regional and in situ principal compressive stress in the crust only if there are enough seismic stations and enough data. At least, PFS is a useful choice in the zone where there are a large number of dense seismic stations.
基金National Natural Science Foundation of China (40274011, 40074020), MOST (2001BA601B02) and Joint Seismological Science Foundation of China (102068).
文摘In 2001 three earthquakes occurred in Shidian in Yunnan Province, which were the MS=5.2 on April 10, the MS=5.9 on April 12 and the MS=5.3 on June 8. Based on the data from the station Baoshan of Yunnan Telemetry Digital Seismograph Network, the variational characteristics of shear-wave splitting on these series of strong earthquakes has been studied by using the systematic analysis method (SAM) of shear-wave splitting. The result shows the time delays of shear-wave splitting basically increase with earthquake activity intensifying. However the time delays abruptly decrease immediately before strong aftershocks. It accords with the stress relaxation before earthquakes, which was found recently in study on shear-wave splitting. The result suggests it is significant for reducing the harm degree of earthquakes to develop the stress-forecasting on earthquake in strong active tectonic zones and economic developed regions or big cities under the danger of strong earthquakes.
基金This study is supported by the National Key R&D Program of China(No.2018YFC1503400)the National Natural Science Foundation of China(No.41804088).Some of the figures were made using the Generic Mapping Tools(Wessel et al.,2013).
文摘A total of 351 shear-wave splitting results at 25 stations were obtained from the seismic data recorded in period of January,2013 to December,2016,by a broadband seismic array deployed in the northern segment of Xiaojiang Fault Zone(n-XJFZ).Meanwhile,the stress field of the n-XJFZ was determined by inverting 140 focal mechanism solutions of the small earthquakes within the study area which were recorded in the same period.This determination confirmed a compressive stress in NW-SE orientation and an extensional stress in the NE-SW orientation,with little difference from those released by previous studies.The shear-wave splitting results show a spatial complexity in polarization orientation,different from one site to another.How-ever,the polarization orientations integrated for the subareas suggest that the fault trends seemingly played important roles.All the subareas bear two dominant orientations,N10°E and N90°E,both of which are different from the azimuths of the principal compressive stress,due to the fault distribution.The time delay averaged over the entire region is 4.56 ms/km,close to that of the upper boundary of the generally accepted interval worldwide but larger than those in most of the investigated regions in the Chinese mainland,which probably implies an alignment of more micro-cracks in the n-XJFZ.Interestingly,the 2014 Ms6.5 Ludian earthquake was found to have caused a variation in the time delays of the slow shear waves within the study area though its epicenter was outside.This earthquake resulted in an evident drop of the time delays remaining for 4 months,however,lifted a bit the time-delay level with respect to that prior to the earthquake.
文摘In order to make a more effective use of the data from regional digital seismograph networks and to promote the study on shear wave splitting and its application to earthquake stress-forecasting, SAM software system, i.e., the software on systematic analysis method of shear wave splitting has been developed. This paper introduces the design aims, system structure, function and characteristics about the SAM software system and shows some graphical interfaces of data input and result output. Lastly, it discusses preliminarily the study of shear wave splitting and its application to earthquake forecasting.
基金Basis and Special Research Foundation, Institute of Earthquake Science, China Earthquake Administration (2007-24)
文摘Using seismic waveform data recorded at station YK (Yingkou) of Liaoning Telemetry Digital Seismic Network, this paper studied the characteristics of shear-wave splitting before and after the Xiuyan MS5.9 (ML5.3) earthquake in November 29, 1999 with SAM method. The results show that the predominant polarizations of fast shear-waves at YK is in direction of ENE-WSW, consistent with the direction of regional principal compressive stress and also consistent with the direction of the regional tectonic stress field in North China; time-delays increasing before Xiuyan earthquake may shows accumulation of stress before earthquake. The predominant polarizations of fast shear-waves at YK are also related to the spatial distribution of small earthquakes and correlate with the fault strike. The histogram of monthly average polarizations of fast shear-waves shows that polarizations of fast shear-waves also seems to change from two months before the earthquake, but it still needs more data for verification.
基金National Natural Science Foundation of China (40274011 40074020) MOST (2001BA601B02) and Joint Seis-mological Science Foundation of China (102068).
文摘In 2001 three earthquakes occurred in Shidian in Yunnan Province, which were the MS=5.2 on April 10, the MS=5.9 on April 12 and the MS=5.3 on June 8. Based on the data from the station Baoshan of Yunnan Telemetry Digital Seismograph Network, the variational characteristics of shear-wave splitting on these series of strong earthquakes has been studied by using the systematic analysis method (SAM) of shear-wave splitting. The result shows the time delays of shear-wave splitting basically increase with earthquake activity intensifying. However the time delays abruptly decrease immediately before strong aftershocks. It accords with the stress relaxation before earthquakes, which was found recently in study on shear-wave splitting. The result suggests it is significant for reducing the harm degree of earthquakes to develop the stress-forecasting on earthquake in strong active tectonic zones and economic developed regions or big cities under the danger of strong earthquakes.
文摘Seismic anisotropy and its main features along the convergent boundary between Africa and Iberia are detected through the analysis of teleseismic shear-wave splitting. Waveform data generated by 95 teleseismic events recorded at 17 broadband stations deployed in the western Mediterranean region are used in the present study. Although the station coverage is not uniform in the Iberian Peninsula and north- west Africa, significant variations in the fast polarization directions and delay times are observed at stations located at different tectonic domains. Fast polarization directions are oriented predominantly NW-SE at most stations which are close to the plate boundary and in central Iberia; being consistent with the absolute plate motion in the region. In the northern part of the Iberian Peninsula, fast velocity direc- tions are oriented nearly E--W; coincident with previous results. Few stations located slightly north of the plate boundary and to the southeast of lberia show E--W to NE-SW fast velocity directions, which may be related to the Alpine Orogeny and the extension direction in lberia. Delay times vary significantly between 0.2 and 1.9 s for individual measurements, reflecting a highly anisotropic structure beneath the recording stations. The relative motion between Africa and lberia represents the main reason for the observed NW-SE orientations of the fast velocity directions. However, different causes of anisotropy have also to be considered to explain the wide range of the splitting pattern observed in the western Mediterranean region. Many geophysical observations such as the low Pn velocity, lower lithospheric Q values, higher heat flow and the presence of high conductive features support the mantle flow in the western Mediterranean, which may contribute and even modify the splitting pattern beneath the studied region.
基金sponsored by the Natural Science of Shandong Province(ZH2014DQ019)Earthquake Science and Technology Spark Plan(XH15026)+1 种基金Key Foundation Program of Earthquake Administration of Shandong Province(JJ1407Y)the Contract Program of Earthquake Administration of Shandong Province(15Y102)
文摘Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.
基金This study was carried out at the Earthquake Research Institute of Lanzhou of CSB,supported by the Natural Science Foundation of Gansu Province(ZS991-A25-013-Z)the CSB key projecl of“9th Five-year Plan"(95-07-436)the Joint Foundation of Seismological Science(198115)of CSB.
文摘The temporal evolution of shear-wave splitting and geoelectrical anisotropy of earth media during the preparation and occurrence of the Yongdeng MS5.8 earthquake is studied based on the digital seismic data and continuous magnetotelluric (MT) records. The results show that the direction of polarization of the fast S-wave gradually rotated from north by east to north by west before the Yongdeng earthquake and returned to north by east after the earthquake. Moreover, the time delay between the fast S wave and slow S wave increased to the largest until the earthquake occurred. On the other hand, the directions of geoelectrical principal axes also changed before earthquake, and exhibited identical characteristics in the frequency domain. The direction of the axis (pxy), which was originally perpendicular to the fault near station, varied from N17°to N15°before earthquake, and returned to north by east after the earthquake. Correspondingly, the change of pxy was most obvious in the period range of 160 s to 226 s, but the variation of pyx was less obvious. The focal mechanism solution of the earthquake showed that the direction of P-axis was N15°. Conclusions are: (1) The fast S-wave polarization, one of the geoelectrical principal axes and the P-axis were in agreement in orientation during earthquake preparation, which is the result of the alignment of EDA cracks; (2) The fact that the geoelectrical axes identically varied with frequency demonstrated that EDA is really widespread in the crust; (3) The variation of MT apparent resistivity also showed the existence of anisotropy and has its own features: The static anisotropy of resistivity is controlled by the tectonic conditions of the station, while the dynamic anisotropy is caused and affected by the seismic stress field; The resistivity along the axis parallel to the P-axis showed the most obvious variation, while the difference in variation with frequency shows that the variation of resistivity depends not only on direction but also on buried depth.
基金jointly supported by Task Contract for Earthquake Situation Tracking of CEA in 2015(2015010113,2015010301)fundation from Earthquake Administration of Xinjiang Uygur Autonomous Region,China(201401)
文摘Earthquakes of M_S5. 6 and M_S6.1 occurred in Yingjiang,Yunnan on May 24 and May 30,2014 respectively. In this paper,we use the waveform data recorded by mobile seismic stations( KAC) which were set up in the source area after the Yingjiang MS5. 6earthquake on May 24,2014 to study the shear-wave splitting characteristics of Yingjiang M_S6.1 earthquake sequence with the SAM method. The result shows that predominant polarization of fast shear-waves before the M_S6.1 earthquake is consistent with the direction of regional principal compressive stress,and predominant polarization of fast shear-waves before the M_S6.1 earthquake show better consistency and smaller dispersion compared to after the M_S6.1 earthquake,and there may be a deflection for the fast shearwaves predominant polarization between the M_S6.1 earthquake sequence and foreshock sequence. We found that the time-delays generally exhibited a lower level before the M_S6.1earthquake and a relatively higher value after the M_S6.1 earthquake.
基金the Science and Technology Activity B on Study-abroad Return Scholar of Non-Education System.
文摘This paper mainly observed and analyzed the character of shear-wave splitting in rock specimens while they were in the critical state of rupture. The rock specimens for study are made of Laizhou marble from Shandong, China. A series of records were obtained from two rock specimens when they were in the critical state of rupture. The result shows that, in the critical state just before rock rupture, there may be the phenomenon of rise and fall in the time delay of shear-wave splitting, even though the load was kept constant. That is to say, the time delay of shear-wave splitting may have a falling process before rock rupture.
基金supported by the National 973 Project of China (No.2013CB733303)the open fund of Key Laboratory of Geospace Environment and Geodesy,Ministry of Education (No.15-02-07)
文摘The upper crustal anisotropy of Yunnan area, SE margin of Tibetan Plateau, is investigated by measuring the shear wave splitting of local earthquakes. The mean value of the measured delay times is 0.054 s and far less than that from Pms splitting analysis, indicating that the crustal anisotropy is contributed mostly from mid-lower crust. The fast polarization directions are mostly sub-parallel to the maximum horizontal compression directions while the stations near fault zones show fault-parallel fast polarization directions, suggesting both stress and geological structure contribute to the upper crust anisotropy.Comparing fast polarization directions from shear wave splitting of local earthquakes and Pms, large angle differences are shown at most stations, implying different anisotropy properties between upper and mid-lower crust. However, in southwestern Yunnan, the fast polarization directions of Pms and Swave splitting are nearly parallel, and the stress and surface strain rate directions show strong correlation, which may indicate that the surface and deep crust deformations can be explained by the same mechanism and the surface deformation can represent the deformation of the whole crust. Therefore,the high correlation between surface strain and mantle deformation in this area suggests the mechanical coupling between crust and mantle in southwestern Yunnan. In the rest region of Yunnan, the crustmantle coupling mechanisms are supported by the lack of significant crustal anisotropy with Ne S fast polarization directions from Pms splitting. Therefore, we conclude that the crust and upper mantle are coupled in Yunnan, SE margin of Tibetan Plateau.
文摘This paper briefly discusses the new methods that the authors have put forward to distinguish splitting shear-waves.By combining these new methods with other methods,the authors have processed the recorded data of an earthquake.The study results are consistent with each other.
基金sponsored by the China Spark Program of Earthquake Science and Technology(XH12027)the Three-Combination Topics of China Earthquake Administration of"Research on the Crustal Medium Anisotropy in the Jiujiang-Ruichang Earthquake Area"the Special Fund of Seismic Industry Research(201008007)
文摘Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area. The result shows that the time delays of slow shear waves of the DJS station, which is not far from the epicenter and where the distribution of faults is complex near the station, are relatively larger and the polarization directions of fast shear waves are not concentrated; the predominant polarization direction of fast shear waves of WUJ station, with single fault distributed nearby, has a difference of 35° to the strike of the fault and is inconsistent with the direction of regional principal compressive stress. The predominant polarization direction of fast shear waves of SZD station with no faults nearby is in accordance with regional principal compressive stress. There is no obvious regular relationshipship between the delay time and the focal depth.
基金support by National Key Research and Development Program of China(2022YFB3803502)National Natural Science Foundation of China(52103076)+5 种基金Science and Technology Commission of Shanghai Municipality(23ZR1400300)special fund of Beijing Key Laboratory of Indoor Air Quality Evaluat ion and Control(NO.BZ0344KF21-02)State Key Laboratory of Electrical Insulation and Power Equipment(EIPE22203)JLF is a member of LSRE-LCM–Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials,supported by national funds through FCT/MCTES(PIDDAC):LSRE-LCM,UIDB/50020/2020(DOI:10.54499/UIDB/50020/2020)UIDP/50020/2020(DOI:10.54499/UIDP/50020/2020)ALiCE,LA/P/0045/2020(DOI:10.54499/LA/P/0045/2020).
文摘Direct seawater splitting has emerged as a popular and promising research direction for synthesising clean,green,non-polluting,and sustainable hydrogen energy without depending on high-purity water in the face of the world’s shortage of fossil energy.However,efficient seawater splitting is hindered by slow kinetics caused by the ultra-low conductivity and the presence of bacteria,microorganisms,and stray ions in seawater.Additionally,producing hydrogen on an industrial scale is challenging due to the high production cost.The present review addresses these challenges from the catalyst point of view,namely,that designing catalysts with high catalytic activity and stability can directly affect the rate and effect of seawater splitting.From the ion transfer perspective,designing membranes can block harmful ions,improving the stability of seawater splitting.From the energy point of view,mixed seawater systems and self-powered systems also provide new and low-energy research systems for seawater splitting.Finally,ideas and directions for further research on direct seawater splitting in the future are pointed out,with the aim of achieving low-cost and high-efficiency hydrogen production.
基金support from the Czech Science Foundation,project EXPRO,No 19-27454Xsupport by the European Union under the REFRESH—Research Excellence For Region Sustainability and High-tech Industries project number CZ.10.03.01/00/22_003/0000048 via the Operational Programme Just Transition from the Ministry of the Environment of the Czech Republic+1 种基金Horizon Europe project EIC Pathfinder Open 2023,“GlaS-A-Fuels”(No.101130717)supported from ERDF/ESF,project TECHSCALE No.CZ.02.01.01/00/22_008/0004587).
文摘Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by single-atom catalysts(SACs),which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports.Recently,bimetallic SACs(bimSACs)have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports.BimSACs offer an avenue for rich metal–metal and metal–support cooperativity,potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges,substrate activation with reversible redox cycles,simultaneous multi-electron transfer,regulation of spin states,tuning of electronic properties,and cyclic transition states with low activation energies.This review aims to encapsulate the growing advancements in bimSACs,with an emphasis on their pivotal role in hydrogen generation via water splitting.We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs,elucidate their electronic properties,and discuss their local coordination environment.Overall,we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction,the two half-reactions of the water electrolysis process.
基金financially supported by the Yancheng Polytechnic College School-Level Scientific Research, China (No. ygy1903)the National Natural Science Foundation of China (Nos. 52001163, 52075237, and 52371157)+2 种基金the Open Project of Taihu Laboratory of Deep-Sea Technology Science, Key Research and Development Plan of Jiangsu Province, China (No. BE2019119)supported by the Priority Academic Program Development of Jiangsu Higher Education Institution (PAPD), Chinathe research funding for the Jiangsu Specially-Appointed Professor Program, China。
文摘Recent advancements in electrocatalysis have highlighted the exceptional application value of amorphous electrocatalysts. Withtheir unique atomic configurations, these electrocatalysts exhibit superior catalytic performance compared to that of their crystalline coun-terparts. Transition metal(TM) amorphous ribbon-shaped electrocatalysts have recently emerged as a new frontier in the catalysis field.Dealloying is widely considered a fascinating method for enhancing the electrocatalyst performance. In this review, we comprehensivelyexamine the principles of water electrolysis, discuss the prevalent methods for fabricating ribbon-configured electrocatalysts, and providean overview of amorphous alloys. Furthermore, we discuss binary, ternary, and high-entropy amorphous TM-based electrocatalysts,which satisfy the requirements necessary for effective water electrolysis. We also propose strategies to enhance the activity of amorphousTM-based ribbons, including morphology control, defect engineering, composition optimization, and heterostructure creation in differentelectrolytes. Our focus extends to the latest developments in the design of heterogeneous micro/nanostructures, management of prepara-tion techniques, and synthesis of different compositions. Finally, we address the ongoing challenges and provide a perspective on the fu-ture development of broadly applicable, self-supporting TM ribbon-shaped electrocatalysts.
基金supported by the Artificial Photosynthesis Project of the New Energy and Industrial Technology Development Organization(NEDO),the JST Fusion Oriented Research for disruptive Science and Technology Program(JPMJFR213D)JSPS KAKENHI(JP24K17774)Domen for his guidance during their PhD studies at the University of Tokyo,as well as for his ongoing support,encouragement,and mentorship.
文摘Professor Kazunari Domen at the Shinshu University and the University of Tokyo has pioneered materials and techniques for solar-driven water splitting using photocatalysts,a promising technology for contributing to the construction of a sustainable and carbon-neutral society.In this paper,we summarize his groundbreaking contributions to photocatalytic water splitting and,more broadly,photocatalytic research.We highlight various novel functional photocatalytic materials,including oxides,(oxy)nitrides,and oxysulfides,along with innovative techniques such as cocatalyst engineering and Z-scheme system construction developed by the Domen Group.His team has also pioneered readily accessible and cost-effective photo(electro)chemical device fabrication methods,such as the particle-transfer method and thin-film-transfer method.Furthermore,their research has made significant contributions to understanding the(photo)catalytic mechanisms using advanced characterization techniques.Together with his research team,Professor Domen has set many milestones in the field of photocatalytic overall water splitting,notably demonstrating the first scalable and stable 100 m^(2)solar H_(2)production system using only water and sunlight.His work has revealed the potential for practical solar H2 production from water and sunlight,and highlighted the application of fundamental principles,combined with chemical and materials science tools,to design effective photocatalytic systems.Through this review,we focus on his research and the foundational design principles that can inspire the development of efficient photocatalytic systems for water splitting and solar fuel production.By building on his contributions,we anticipate a significant impact on addressing major global energy challenges.
