As one of the most seismically active regions,Sichuan Basin is a key area of seismological studies in China.This study applies a neural network model with attention mechanisms,simultaneously picking the P-wave arrival...As one of the most seismically active regions,Sichuan Basin is a key area of seismological studies in China.This study applies a neural network model with attention mechanisms,simultaneously picking the P-wave arrival times and determining the first-motion polarity.The polarity information is subsequently used to derive source focal mechanisms.The model is trained and tested using small to moderate earthquake data from June to December 2019 in Sichuan.We apply the trained model to predict first-motion polarity directions of earthquake recordings in Sichuan from January to May 2019,and then derive focal mechanism solutions using HASH algorithm with predicted results.Compared with the source mechanism solutions obtained by manual processing,the deep learning method picks more polarities from smaller events,resulting in more focal mechanism solutions.The catalog documents focal mechanism solutions of 22 events(M_(L) 2.6–4.8)from analysts during this period,whereas we obtain focal mechanism solutions of 53 events(M_(L) 1.9–4.8)through the deep learning method.The derived focal mechanism solutions for the same events are consistent with the manual solutions.This method provides an efficient way for the source mechanism inversion of small to moderate earthquakes in Sichuan region,with high stability and reliability.展开更多
In recent years, tsunami happens frequently in the world, which caused huge losses. In order to find objective features of tsunamigenic source, global CMT data from 1976 to 2010 and tsunami data from NOAA are analyzed...In recent years, tsunami happens frequently in the world, which caused huge losses. In order to find objective features of tsunamigenic source, global CMT data from 1976 to 2010 and tsunami data from NOAA are analyzed statistically, tsunami is compared with bigger tsunamis. At last, some features of seismic tsunami sources are concluded.展开更多
Lithium-oxygen batteries attract considerable attention due to exceptionally high theoretical energy density,while the development remains in its early stage.As is widely suggested,the solution mechanism induces great...Lithium-oxygen batteries attract considerable attention due to exceptionally high theoretical energy density,while the development remains in its early stage.As is widely suggested,the solution mechanism induces greater discharge capacity,while the surface mechanism induces greater cycle stability.Therefore,battery performance can be improved by adjusting the reaction mechanism.Previous studies predominantly focus on extremely thin or flat electrodes.In contrast,this work utilizes thick electrodes,emphasizing the importance of mass transport.Given that the electrolyte solvent is the main site of mass transport,the effects of two typical solvents on mass transport and battery performance are investigated:dimethyl sulfoxide with low viscosity and a high O_(2) diffusion rate and tetraethylene glycol dimethyl ether with high O_(2) solubility and high Li+transport capability.The results reveal a novel pathway for reaction mechanism induction where the mechanism varies with the spatial position of the electrode.As the spatial distribution of the electrode progresses,a layered appearance of solution mechanism products,transition state products,and surface mechanism products emerges,which is attributed to the increase in the mass transfer resistance.This work presents a distinct perspective on the way solvents influence reaction pathways and offers a new approach to regulating reaction pathways.展开更多
We relocate the spatial distribution of its aftershocks. The relocation database is obtained the devastating 12 May 2008 Wenchuan earthquake and from 89 stations deployed by the China Earthquake Administration, includ...We relocate the spatial distribution of its aftershocks. The relocation database is obtained the devastating 12 May 2008 Wenchuan earthquake and from 89 stations deployed by the China Earthquake Administration, including 54 525 seismograms from 1 376 local earthquakes over Ms3.5 between 12 May 2008 and 3 August 2008. The cross-correlation technique used in this paper has greatly improved the relocation precision by giving much more accurate P-wave differential travel-time measurements than those obtained from routinely picked phase onsets. At the same time, we pick P-wave polarity observations of the Wenchuan earthquake series （hereafter referred to as WES） from 1023 stations in China and 59 IRIS （Incorporated Research Institutions of Seismology） stations. Then, employing a newly developed program CHNYTX, we obtain 83 well-determined focal mechanism solutions （hereafter referred to as FMSs）. Based on spatial distribution and FMSs of the WES, we draw following conclusions： （1） The region near the main shock exhibits a buried low-angle northwest-dipping seismic zone with the main shock at its upper end and two conjugated seismic zones dipping southeast with roughly equal dip-angle; （2） The compressional directions of all kinds of FMSs of the WES are subhorizontal, which reflects the dominant stress in this area is eompressional; （3） The principal compressional direction of the regional stress around Wenchuan is roughly perpendicular to the strike of Beichuan-Yingxiu fault, while around Qingchuan it is roughly parallel to the strike of Qingehuan fault. In intermediate part of the Longmenshan area, the principal compressional direction of the stress should be in-between; （4） The possibly existed molten materials in the lower crust of Songpan-Garze terrain have small contribution to the local stress state in Longmenshan area. The listric geometries of the Longmenshan faults most probably resulted from subhorizontal compression along NW-SE direction in history.展开更多
Abstract The 2008 Wenchuan earthquake, a major intraplate earthquake with Mw 7.9, occurred on the slowly deforming Longmenshan fault. To better understand the causes of this devastating earthquake, we need knowledge o...Abstract The 2008 Wenchuan earthquake, a major intraplate earthquake with Mw 7.9, occurred on the slowly deforming Longmenshan fault. To better understand the causes of this devastating earthquake, we need knowledge of the regional stress field and the underlying geodynamic processes. Here, we determine focal mechanism solutions （FMSs） of the 2008 Wenchuan earthquake sequence （WES） using both P-wave first-motion polarity data and SH/P amplitude ratio （AR） data. As P-wave polarities are more reliable information, they are given priority over SH/ PAR, the latter of which are used only when the former has loose constraint on the FMSs. We collect data from three categories： （1） permanent stations deployed by the China Earthquake Administration （CEA）; （2） the Western Sichuan Passive Seismic Array （WSPSA） deployed by Institute of Geology, CEA; （3） global stations from Incorporated Research Institutions for Seismology. Finally, 129 events with magnitude over Ms 4.0 in the 2008 WES are identified to have well-constrained FMSs. Among them, 83 are well constrained by P-wave polarities only as shown by Cai et al. （Earthq Sci 24（1）：115-125,2011）, and the rest of which are newly constrained by incorporating SH/P AR. Based on the spatial distribution and FMSs of the WES, we draw following conclusions： （1） the principle compressional directions of most FMSs of the WES are subhorizontal, generally in agreement with the conclusion given by Cai et al. （2011） but with a few modifications that the compressional directions are WNW-ESE around Wenchuan and ENE-WSW around Qingchuan, respectively. The subhorizontal compressional direction along the Longmenshan fault from SW to NE seems to have a leftlateral rotation, which agrees well with regional stress field inverted by former researchers （e.g., Xu et al., Acta Seismol Sin 30（5）, 1987; Acta Geophys Sin 32（6）, 1989; Cui et al., Seismol Geol 27（2）：234-242, 2005）; （2） the FMSs of the events not only reflected the regional stress state of the Longmenshan region, but also were obviously controlled by the faults to some extent, which was pointed out by Cai et al. （2011） and Yi et al. （Chin J Geophys 55（4）：1213-1227, 2012）; （3） while the 2008 Wenchuan earthquake and some of its strong aftershocks released most of the elastic energy accumulated on the Longmen- shan fault, some other aftershocks seem to occur just for releasing the elastic energy promptly created by the 2008 Wenchuan earthquake and some of its strong aftershocks. （4） Our results further suggest that the Longmenshan fault from Wenchuan to Beichuan was nearly fully destroyed by the 2008 Wenchuan earthquake and accordingly propose that there is less probability for great earthquakes in the middle part of the Longmenshan fault in the near future, although there might be a barrier to the southwest of Wenchuan and it is needed to pay some attention on it in the near future.展开更多
In this paper, the relationships of the plunges and azimuths of T and P axes versus the strikes, dips, and rakes of two seismic nodal planes were derived to provide ref- erence for earthquake researchers. The independ...In this paper, the relationships of the plunges and azimuths of T and P axes versus the strikes, dips, and rakes of two seismic nodal planes were derived to provide ref- erence for earthquake researchers. The independence of the plunges and azimuths of T, B, and P axes in focal mech- anism solution was discussed, and it was concluded that three parameters, i.e., the azimuths of T, B and P axes, are completely independent. The focal mechanism solution representation based on Euler rotation was introduced, using three Euler angles in place of the plunges and azi- muths of T, B, and P axes, and three focal mechanism solution representations were briefly compared and ana- lyzed in respect of accuracy on the basis of the assumption of rounding; it was concluded that the Euler angle repre- sentation has better accuracy, compared with the azimuth representation and the traditional representation with T, B, and P axes.展开更多
Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely S...Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely Sichuan-Qinghai, Yajiang, Central Sichuan and Central Yunnan blocks. Combining these calculation results with those of the focal mechanism solutions of moderately strong earthquakes, we analyzed the stress field characteristics and dislocation types of seismogenic faults that are distributed in the four sub-blocks. The orientation of principal compressive stress for each block is： EW in Sichuan-Qinghai, ESE or SE in Yajiang, Central Sichuan and Central Yunnan blocks. Based on a great deal of focal mechanism data, we designed a program and calculated the directions of the principal stress tensors, σ1, σ2 and σ3, for the four blocks. Meanwhile, we estimated the difference （also referred to as consistency parameter θ^- ） between the force axis direction of focal mechanism solution and the direction of the mean stress tensor of each block. Then we further analyzed the variation of θ^- versus time and the dislocation types of seismogenic faults. Through determination of focal mechanism solutions for each block, we present information on the variation in θ^- value and dislocation types of seismogenic faults.展开更多
The focal mechanism solution is one of the important focal parameters for exploring fault activity and studying regional stress distribution and it has a wide range of applications. The geological structure of the Sic...The focal mechanism solution is one of the important focal parameters for exploring fault activity and studying regional stress distribution and it has a wide range of applications. The geological structure of the SichuanYunnan region in China is complex, with frequent earthquakes and abundant historical observation data, making it one of the popular areas of concern for scholars. This study utilizes the high-precision community velocity model v2.0 of southwest China, obtained through joint inversion based on multiple data methods. The Cut-AndPaste(CAP) method was employed to fit and invert the observed waveforms of 1475 events with M_(L)≥ 3.5 in the Sichuan-Yunnan region from January 2012 to December 2022, thereby constructing a catalog of double-couple focal mechanisms. By comparing the focal mechanism inversion results of small earthquakes with those from multiple one-dimensional velocity models and conducting comparative statistical analysis on events below magnitude 4, it has been demonstrated that the model used in this study provides a better fit than onedimensional models. This contributes to establishing the lower magnitude limit for producing deeper focal mechanism solutions. This study compares the results of larger magnitude earthquakes in the catalog with those published by the Global Centroid-Moment Tensor(GCMT) project and smaller magnitude earthquakes with the catalog released by the Institute of Earthquake Forecasting, China Earthquake Administration. These comparisons serve to validate the accuracy of the catalog results. Leveraging the high-resolution velocity model, this catalog has re-examined the historical earthquake focal mechanism catalog of the Sichuan-Yunnan region. The inversion has yielded reliable results for smaller magnitudes and a greater number of events, providing additional data and support for understanding the regional stress field, active faults, the mechanisms of large earthquake genesis, and earthquake prediction efforts. Consequently, this enhances the depth of scientific research in the Sichuan-Yunnan region.展开更多
The focal mechanism parameters of small earthquakes are determined by the maximum velocity and displacement amplitude ratio of the direct ^-P- and ^-S-waves recorded by digital stations. The displacement is obtained f...The focal mechanism parameters of small earthquakes are determined by the maximum velocity and displacement amplitude ratio of the direct ^-P- and ^-S-waves recorded by digital stations. The displacement is obtained from the velocity by emulation, and the two results are compared and analyzed. Results of theoretical analysis and practical measurement indicate that the two results of velocity and displacement are consistent, and it is feasible that the maximum displacement amplitude ratio be replaced by the maximum velocity amplitude ratio of the direct ^-P-and ^-S- waves recorded by regional seismic networks when determining focal mechanism solutions of small earthquakes.展开更多
Comprehensive statistical analysis was performed on the basic features of focal mechanisms of 619 ML≥2. 0 earthquakes which occurred in the capital circle area from January 2002 to June 2010. By dividing the capital ...Comprehensive statistical analysis was performed on the basic features of focal mechanisms of 619 ML≥2. 0 earthquakes which occurred in the capital circle area from January 2002 to June 2010. By dividing the capital area into three studying regions based on regional tectonic characteristics,cluster analysis was conducted on the focal mechanisms of all subregions using the longest distance method in the statistical cluster analysis to study the characteristics of tectonic stress tensors. The result shows that dominant P-axis azimuth distribution is NNE-NEE and that of T-axis is NNW-NWW,most of the focal areas are controlled by a horizontal stress field and rupture is mainly of horizontal strike-slip. The maximum principal compression stress orientation is NE75° in the west,NE62° in the middle,and near EW in the east of the capital area. The regional tectonic stress field is characterized by horizontal compression.展开更多
Using the focal mechanism solutions of 24 moderately strong earthquakes in the northern Tianshan area,we carried out system cluster and stress field inversion analysis.The result indicates that,the focal mechanism sol...Using the focal mechanism solutions of 24 moderately strong earthquakes in the northern Tianshan area,we carried out system cluster and stress field inversion analysis.The result indicates that,the focal mechanism solutions of moderately strong earthquakes are mainly dip-slip reverse faulting in the northern Tianshan area.The principal rupture planes of earthquakes are NW-oriented.It is basically consistent with the strike of earthquake structure in its adjacent area.The direction of the principal compression stress P axis is nearly NS,and its inclination angle is small;while the inclination angle of the principal extensional stress T axis is large.It shows that the regional stress field is mainly controlled by the near-NS horizontal compressive stress.The direction of the maximum principal stress shows a gradation process of NNE-NS-NW from east to west.展开更多
In this article, we have inverted local broadband waveform data to determine the focal mechanism of the 2011 Ms4.8 Anqing earthquake. Our results show that the best double couple solution of the Ms4.8 event is 16°...In this article, we have inverted local broadband waveform data to determine the focal mechanism of the 2011 Ms4.8 Anqing earthquake. Our results show that the best double couple solution of the Ms4.8 event is 16°, 74° and 120° for strike, dip and rake angles of one nodal plane respectively, and 131 °, 33°, 30° for the other nodal plane. The estimated focal depth is about 3kin. Both strikes of the two nodal planes differ significantly to the strike of Susong-Zongyang fault, along which seismic activity has been at a low level since the Late Quaternary. This implies that this earthquake may not have occurred on the Susong-Zongyang fault, and we infer that a buried fault with strike of NNE may be the seismogenic structure of this event.展开更多
Source properties and stress fields are critical to understand fundamental mechanisms for fluid-induced earthquakes.In this study,we identify the focal mechanism solutions(FMSs)of 360 earthquakes with local magnitude ...Source properties and stress fields are critical to understand fundamental mechanisms for fluid-induced earthquakes.In this study,we identify the focal mechanism solutions(FMSs)of 360 earthquakes with local magnitude M_(L)≥1.5 in the Changning shale gas field from January 2016 to May 2017 by fitting three-component waveforms.We then constrain the directions of the maximum horizontal stress(σ_(H_(max)))for four dense earthquake clusters using the stress tensor inversion method.The stress drops of 121 earthquakes with M_(L)≥1.5 are calculated using the spectral ratio method.We examine the spatiotemporal heterogeneity of stress field,and discuss the cause of non-double-couple(non-DC)components in seismicity clusters.Following the Mohr-Coulomb criterion,we estimate the fluid overpressure thresholds from FMS for different seismic clusters,providing insights into potential physical mechanisms for induced seismicity.The FMS results indicate that shallow reverse earthquakes,with steep dip angles,characterize most events.The source mechanisms of earthquakes with M_(L)≥1.5 are dominated by DC components(>70%),but several earthquakes with M_(L)>3.0 and the microseismic events nearby during injection period display significant non-DC components(>30%).Stress inversion results reveal that the σ_(H_(max)) direction ranges from 120°to 128°.Stress drops of earthquakes range between 0.10 and 64.49 MPa,with high values occurring on reverse faults situated at a greater distance from the shale layer,accompanied by a moderate rotation(≤25°)in the trend of σ_(H_(max)).The seismic clusters close to the shale layer exhibit low fluid overpressure thresholds,prone to being triggered by high pore-pressure fluid.The integrated results suggest that the diffusion of high pore pressures is likely to be the primary factor for observed earthquakes.The present results are expected to offer valuable insights into the origin of anomalous seismicity near the shale gas sites.展开更多
Objective To study the core contents of the“Implementation Measures for Early Settlement Mechanism of Drug Patent Disputes(Trial)”in China,and to clarify the concerns for enterprises in future work.Methods A compreh...Objective To study the core contents of the“Implementation Measures for Early Settlement Mechanism of Drug Patent Disputes(Trial)”in China,and to clarify the concerns for enterprises in future work.Methods A comprehensive review of the literature was used to find out the key regulations for detailed decomposition and analysis.Results and Conclusion By analyzing the key clauses of China’s“Implementation Measures for Early Settlement Mechanism of Drug Patent Disputes(Trial)”,some practical countermeasures and suggestions are put forward for related research and development(R&D)innovation and drug declaration of enterprises.展开更多
Solid solution strengthening is one of the most conventional strategies for optimizing alloys strength,while the corresponding mechanisms can be more complicated than we traditionally thought specifically as heterogen...Solid solution strengthening is one of the most conventional strategies for optimizing alloys strength,while the corresponding mechanisms can be more complicated than we traditionally thought specifically as heterogeneity of microstructure is involved.In this work,by comparing the change of chemical distribution,dislocation behaviors and mechanical properties after doping equivalent amount of tungsten(W)atoms in CrCoNi alloy and pure Ni,respectively,it is found that the alloying element W in CrCoNi alloy resulted in much stronger strengthening effect due to the significant increase of heterogeneity in chemical distribution after doping trace amount of W.The large atomic scale concentration fluctuation of all elements in CrCoNi-3W causes dislocation motion via strong nanoscale segment detrapping and severe dislocation pile up which is not the case in Ni-3W.The results revealed the high sensitivity of elements distribution in multi-principle element alloys to composition and the significant consequent influence in tuning the mechanical properties,giving insight for complex alloy design.展开更多
The medium-small earthquakes that occurred in the middle part of Tibetan Plateau(32°N–36°N, 90°E–93°E) from August 2016 to June 2017 were relocated using the absolute earthquake location method H...The medium-small earthquakes that occurred in the middle part of Tibetan Plateau(32°N–36°N, 90°E–93°E) from August 2016 to June 2017 were relocated using the absolute earthquake location method Hypo2000. Compared to the reports of Chinese Seismological Networks, our relocation results are more clustered on the whole, the horizontal location differences exceed 10 km, and the focal depths are concentrated in 0–8 km, which indicates that the upper crust inside the Tibetan Plateau is tectonically active. In June2017 altogether eight earthquakes above magnitude 3.0 took place; their relocated epicenters are concentrated around Gêladaindong.The relocation results of M<3.0 small earthquakes also showed obvious differences. Therefore, we used the CAP method to invert for the focal mechanisms of the M ≥3.0 earthquakes; results generally tally with the surface geological structures, indicating that the Tibetan Plateau is still under the strong compressional force from the India Plate. Among them the eight earthquakes that occurred near Gêladaindong in June 2017 are all of normal fault type or with some strike-slip at the same time; based on previous research results we conjecture that these events are intense shallow crust responses to deep crust-mantle activities.展开更多
Based on abundant aftershock sequence data of the Wenchuan Ms8.0 earthquake on May 12, 2008, we studied the spatio-temporal variation process and segmentation rupture characteristic. Dense aftershocks distribute along...Based on abundant aftershock sequence data of the Wenchuan Ms8.0 earthquake on May 12, 2008, we studied the spatio-temporal variation process and segmentation rupture characteristic. Dense aftershocks distribute along Longmenshan central fault zone of NE direction and form a narrow strip with the length of 325 krn and the depth between several and 40 km. The depth profile （section of NW direction） vertical to the strike of aftershock zone （NE direction） shows anisomerous wedgy distribution characteristic of afiershock concentrated regions; it is related to the force form of the Longmenshan nappe tectonic belt. The stronger aftershocks could be divided into northern segment and southern segment apparently and the focal depths of strong aftershocks in the 50 km area between northern segment and southern segment are shallower. It seems like ＇to be going to rupture＇ segment. We also study focal mechanisms and segmentation of strong aftershocks. The principal compressive stress azimuth of aftershock area is WNW direction and the faulting types of aftershocks at southern and northern segment have the same proportion. Because afiershocks distribute on different secondary faults, their focal mechanisms present complex local tectonic stress field. The faulting of seven strong earthquakes on the Longmenshan central fault is mainly characterized by thrust with the component of right-lateral strike-slip. Meantime six strong aftershocks on the Longmenshan back-range fault and Qingchuan fault present strike-slip faulting. At last we discuss the complex segmentation rupture mechanism of the Wenchuan earthquake.展开更多
The mechanisms of the February 3, 1996 Lijiang main shock, Yunnan Province, are estimated by using the principle to inverse the mechanisms of two point sources simultaneously. The results are that the main shock of Li...The mechanisms of the February 3, 1996 Lijiang main shock, Yunnan Province, are estimated by using the principle to inverse the mechanisms of two point sources simultaneously. The results are that the main shock of Lijiang consists of two large ruptures, the time difference and the distance between the two ruptures are about 12 s (by the inversion) and about 26 km respectively. An extensional normal with strike-slip fault in about the north-south direction was formed by the first rupture, the mechanism of the second rupture is to be further studied. The method to inverse mechanisms of two point sources at the same time and the results obtained by directly analyzing P waveform records of the main shock are introduced, some related problems are also discussed. The Wuding earthquakes of October, 1995 and the Lijiang earthquake are considered to be the manifestation of the same dynamic process at different temporal and spatial points and the occurrence order of the two earthquakes is related to the direction of dynamics transmission.展开更多
We have developed an automatic regional focal mechanism inversion system based on the Earthquake Rapid Report(ERR) system and the real-time three-component seismic waveform stream of 1 000 broadband seismic stations p...We have developed an automatic regional focal mechanism inversion system based on the Earthquake Rapid Report(ERR) system and the real-time three-component seismic waveform stream of 1 000 broadband seismic stations provided by the China Earthquake Networks Center(CENC). The system can rapidly provide a double couple solution and centroid depth within 5–15 min after receiving earthquake information from the ERR system.The data processing is triggered by earthquake information obtained from the ERR system. The system is capable of determining the focal mechanism of all shallow-depth earthquakes in the Chinese mainland with a magnitude of 5.5–6.5. It utilizes waveform data recorded by seismic stations located within 500 km from the epicenter,enabling the reporting of a focal mechanism solution within 5–15 min of an earthquake occurrence. Additionally,the system can assign a corresponding grade(A B C) to the focal mechanism solution. We processed a total of 301earthquakes that occurred from 2021 to June 2022, and after the quality control, 166 of them were selected.These selected solutions were manually checked, and 160 of them were compiled in a focal mechanism catalog.This catalog can be conveniently downloaded online via the Internet. The automatic focal mechanism solution of earthquakes in eastern China exhibits a good agreement with that provided by the Global Centroid Moment Tensor(GCMT), when available. The average Kagan angle between this catalog and GCMT is 22°, and the average difference in MWis 0.17. Furthermore, compared with GCMT, the minimum magnitude of our catalog has been reduced from approximately 5.0 to 4.0. The correlation between the centroid depth and crustal thickness in the Chinese mainland confirms the distribution of the centroid depth.展开更多
The solid-phase extraction（SPE） technique applied to the extraction of organic compound was creatively used as the extraction of inorganic gold in the paper.Two types of techniques were proposed and explored,namely ...The solid-phase extraction（SPE） technique applied to the extraction of organic compound was creatively used as the extraction of inorganic gold in the paper.Two types of techniques were proposed and explored,namely the SPE and the liquid–liquid extraction（LLE） of the quaternary ammonium surfactant [cetytrimethyl ammonium bromide（CTMAB）,cetyl pyridine bromide（CPB）,benzyl dimethyl dodecyl ammonium chloride（BDMDAC）,and dodecyl trimethyl ammonium chloride（DTMAC）].The surfactant could react with Au（CN）2^- to form the ionic complex,and the compound could be extracted by SPE column of reversed-phase bonded silica gel.Hence,a new method of SPE was proposed to extract gold with these features of the high selectivity,the reliability,and the simplicity.The experimental result shows that the recovery rate of gold is more than 98 %,and the solid-phase extraction column is not easily damaged and it can be repeatedly used.The new method can be used as the extraction process of gold from alkaline cyanide solution as well.Besides,the paper also puts forward a new process of gold extraction.展开更多
基金the National Key R&D Program of China(2021YFC3000701)for the financial support。
文摘As one of the most seismically active regions,Sichuan Basin is a key area of seismological studies in China.This study applies a neural network model with attention mechanisms,simultaneously picking the P-wave arrival times and determining the first-motion polarity.The polarity information is subsequently used to derive source focal mechanisms.The model is trained and tested using small to moderate earthquake data from June to December 2019 in Sichuan.We apply the trained model to predict first-motion polarity directions of earthquake recordings in Sichuan from January to May 2019,and then derive focal mechanism solutions using HASH algorithm with predicted results.Compared with the source mechanism solutions obtained by manual processing,the deep learning method picks more polarities from smaller events,resulting in more focal mechanism solutions.The catalog documents focal mechanism solutions of 22 events(M_(L) 2.6–4.8)from analysts during this period,whereas we obtain focal mechanism solutions of 53 events(M_(L) 1.9–4.8)through the deep learning method.The derived focal mechanism solutions for the same events are consistent with the manual solutions.This method provides an efficient way for the source mechanism inversion of small to moderate earthquakes in Sichuan region,with high stability and reliability.
文摘In recent years, tsunami happens frequently in the world, which caused huge losses. In order to find objective features of tsunamigenic source, global CMT data from 1976 to 2010 and tsunami data from NOAA are analyzed statistically, tsunami is compared with bigger tsunamis. At last, some features of seismic tsunami sources are concluded.
基金supported by the National Natural Science Foundation of China(52376080 and 52306122)the Anhui Provincial Natural Science Foundation(2308085QE174)+3 种基金the China Postdoctoral Science Foundation(2023TQ0346)the Postdoctoral Fellowship Program of CPSF(GZC20232522)the Fundamental Research Funds for the Central Universities(WK2090000057)the Students’Innovation and Entrepreneurship Foundation of USTC(CY2023C008).
文摘Lithium-oxygen batteries attract considerable attention due to exceptionally high theoretical energy density,while the development remains in its early stage.As is widely suggested,the solution mechanism induces greater discharge capacity,while the surface mechanism induces greater cycle stability.Therefore,battery performance can be improved by adjusting the reaction mechanism.Previous studies predominantly focus on extremely thin or flat electrodes.In contrast,this work utilizes thick electrodes,emphasizing the importance of mass transport.Given that the electrolyte solvent is the main site of mass transport,the effects of two typical solvents on mass transport and battery performance are investigated:dimethyl sulfoxide with low viscosity and a high O_(2) diffusion rate and tetraethylene glycol dimethyl ether with high O_(2) solubility and high Li+transport capability.The results reveal a novel pathway for reaction mechanism induction where the mechanism varies with the spatial position of the electrode.As the spatial distribution of the electrode progresses,a layered appearance of solution mechanism products,transition state products,and surface mechanism products emerges,which is attributed to the increase in the mass transfer resistance.This work presents a distinct perspective on the way solvents influence reaction pathways and offers a new approach to regulating reaction pathways.
基金supported by the Wenchuan Fault Scientific Drilling Program(WFSD),the Key Projects in the National Science and Technology Pillar Program during the Eleventh Five-year Plan Period under grant No. 2008BAC38B02-4the National Natural Science Foundation of China under grant No. 40821062
文摘We relocate the spatial distribution of its aftershocks. The relocation database is obtained the devastating 12 May 2008 Wenchuan earthquake and from 89 stations deployed by the China Earthquake Administration, including 54 525 seismograms from 1 376 local earthquakes over Ms3.5 between 12 May 2008 and 3 August 2008. The cross-correlation technique used in this paper has greatly improved the relocation precision by giving much more accurate P-wave differential travel-time measurements than those obtained from routinely picked phase onsets. At the same time, we pick P-wave polarity observations of the Wenchuan earthquake series （hereafter referred to as WES） from 1023 stations in China and 59 IRIS （Incorporated Research Institutions of Seismology） stations. Then, employing a newly developed program CHNYTX, we obtain 83 well-determined focal mechanism solutions （hereafter referred to as FMSs）. Based on spatial distribution and FMSs of the WES, we draw following conclusions： （1） The region near the main shock exhibits a buried low-angle northwest-dipping seismic zone with the main shock at its upper end and two conjugated seismic zones dipping southeast with roughly equal dip-angle; （2） The compressional directions of all kinds of FMSs of the WES are subhorizontal, which reflects the dominant stress in this area is eompressional; （3） The principal compressional direction of the regional stress around Wenchuan is roughly perpendicular to the strike of Beichuan-Yingxiu fault, while around Qingchuan it is roughly parallel to the strike of Qingehuan fault. In intermediate part of the Longmenshan area, the principal compressional direction of the stress should be in-between; （4） The possibly existed molten materials in the lower crust of Songpan-Garze terrain have small contribution to the local stress state in Longmenshan area. The listric geometries of the Longmenshan faults most probably resulted from subhorizontal compression along NW-SE direction in history.
基金supported by the Wenchuan Fault Scientific Drilling Program(WFSD)
文摘Abstract The 2008 Wenchuan earthquake, a major intraplate earthquake with Mw 7.9, occurred on the slowly deforming Longmenshan fault. To better understand the causes of this devastating earthquake, we need knowledge of the regional stress field and the underlying geodynamic processes. Here, we determine focal mechanism solutions （FMSs） of the 2008 Wenchuan earthquake sequence （WES） using both P-wave first-motion polarity data and SH/P amplitude ratio （AR） data. As P-wave polarities are more reliable information, they are given priority over SH/ PAR, the latter of which are used only when the former has loose constraint on the FMSs. We collect data from three categories： （1） permanent stations deployed by the China Earthquake Administration （CEA）; （2） the Western Sichuan Passive Seismic Array （WSPSA） deployed by Institute of Geology, CEA; （3） global stations from Incorporated Research Institutions for Seismology. Finally, 129 events with magnitude over Ms 4.0 in the 2008 WES are identified to have well-constrained FMSs. Among them, 83 are well constrained by P-wave polarities only as shown by Cai et al. （Earthq Sci 24（1）：115-125,2011）, and the rest of which are newly constrained by incorporating SH/P AR. Based on the spatial distribution and FMSs of the WES, we draw following conclusions： （1） the principle compressional directions of most FMSs of the WES are subhorizontal, generally in agreement with the conclusion given by Cai et al. （2011） but with a few modifications that the compressional directions are WNW-ESE around Wenchuan and ENE-WSW around Qingchuan, respectively. The subhorizontal compressional direction along the Longmenshan fault from SW to NE seems to have a leftlateral rotation, which agrees well with regional stress field inverted by former researchers （e.g., Xu et al., Acta Seismol Sin 30（5）, 1987; Acta Geophys Sin 32（6）, 1989; Cui et al., Seismol Geol 27（2）：234-242, 2005）; （2） the FMSs of the events not only reflected the regional stress state of the Longmenshan region, but also were obviously controlled by the faults to some extent, which was pointed out by Cai et al. （2011） and Yi et al. （Chin J Geophys 55（4）：1213-1227, 2012）; （3） while the 2008 Wenchuan earthquake and some of its strong aftershocks released most of the elastic energy accumulated on the Longmen- shan fault, some other aftershocks seem to occur just for releasing the elastic energy promptly created by the 2008 Wenchuan earthquake and some of its strong aftershocks. （4） Our results further suggest that the Longmenshan fault from Wenchuan to Beichuan was nearly fully destroyed by the 2008 Wenchuan earthquake and accordingly propose that there is less probability for great earthquakes in the middle part of the Longmenshan fault in the near future, although there might be a barrier to the southwest of Wenchuan and it is needed to pay some attention on it in the near future.
基金supported by Special Foundation for Seismic Research (Grant No.201208006)Director Foundation of Institute of Seismology,China Earthquake Adminstration (Grant Nos.IS201116013,IS201506220)National Natural Science Foundation of China (Grant Nos.40974012,41304019)
文摘In this paper, the relationships of the plunges and azimuths of T and P axes versus the strikes, dips, and rakes of two seismic nodal planes were derived to provide ref- erence for earthquake researchers. The independence of the plunges and azimuths of T, B, and P axes in focal mech- anism solution was discussed, and it was concluded that three parameters, i.e., the azimuths of T, B and P axes, are completely independent. The focal mechanism solution representation based on Euler rotation was introduced, using three Euler angles in place of the plunges and azi- muths of T, B, and P axes, and three focal mechanism solution representations were briefly compared and ana- lyzed in respect of accuracy on the basis of the assumption of rounding; it was concluded that the Euler angle repre- sentation has better accuracy, compared with the azimuth representation and the traditional representation with T, B, and P axes.
基金National Key Basic Research Development and Programming Project (2004CB418404) and Joint Seismological Science Foundation (105004).
文摘Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely Sichuan-Qinghai, Yajiang, Central Sichuan and Central Yunnan blocks. Combining these calculation results with those of the focal mechanism solutions of moderately strong earthquakes, we analyzed the stress field characteristics and dislocation types of seismogenic faults that are distributed in the four sub-blocks. The orientation of principal compressive stress for each block is： EW in Sichuan-Qinghai, ESE or SE in Yajiang, Central Sichuan and Central Yunnan blocks. Based on a great deal of focal mechanism data, we designed a program and calculated the directions of the principal stress tensors, σ1, σ2 and σ3, for the four blocks. Meanwhile, we estimated the difference （also referred to as consistency parameter θ^- ） between the force axis direction of focal mechanism solution and the direction of the mean stress tensor of each block. Then we further analyzed the variation of θ^- versus time and the dislocation types of seismogenic faults. Through determination of focal mechanism solutions for each block, we present information on the variation in θ^- value and dislocation types of seismogenic faults.
基金the National Key Research and Development Program for supporting this study (Project No.: 2021YFC3000701-03, 2021YFC3000705)。
文摘The focal mechanism solution is one of the important focal parameters for exploring fault activity and studying regional stress distribution and it has a wide range of applications. The geological structure of the SichuanYunnan region in China is complex, with frequent earthquakes and abundant historical observation data, making it one of the popular areas of concern for scholars. This study utilizes the high-precision community velocity model v2.0 of southwest China, obtained through joint inversion based on multiple data methods. The Cut-AndPaste(CAP) method was employed to fit and invert the observed waveforms of 1475 events with M_(L)≥ 3.5 in the Sichuan-Yunnan region from January 2012 to December 2022, thereby constructing a catalog of double-couple focal mechanisms. By comparing the focal mechanism inversion results of small earthquakes with those from multiple one-dimensional velocity models and conducting comparative statistical analysis on events below magnitude 4, it has been demonstrated that the model used in this study provides a better fit than onedimensional models. This contributes to establishing the lower magnitude limit for producing deeper focal mechanism solutions. This study compares the results of larger magnitude earthquakes in the catalog with those published by the Global Centroid-Moment Tensor(GCMT) project and smaller magnitude earthquakes with the catalog released by the Institute of Earthquake Forecasting, China Earthquake Administration. These comparisons serve to validate the accuracy of the catalog results. Leveraging the high-resolution velocity model, this catalog has re-examined the historical earthquake focal mechanism catalog of the Sichuan-Yunnan region. The inversion has yielded reliable results for smaller magnitudes and a greater number of events, providing additional data and support for understanding the regional stress field, active faults, the mechanisms of large earthquake genesis, and earthquake prediction efforts. Consequently, this enhances the depth of scientific research in the Sichuan-Yunnan region.
基金the"Strong Earthquake Monitoring and Prediction Research"for the 11th"Five-Year Plan"under the grant No.2006BA(01B02-01-01)subspecial subject of 2006BAC01 B02-01-01the State Key Basic Research Development Programme (2004CB418404),China
文摘The focal mechanism parameters of small earthquakes are determined by the maximum velocity and displacement amplitude ratio of the direct ^-P- and ^-S-waves recorded by digital stations. The displacement is obtained from the velocity by emulation, and the two results are compared and analyzed. Results of theoretical analysis and practical measurement indicate that the two results of velocity and displacement are consistent, and it is feasible that the maximum displacement amplitude ratio be replaced by the maximum velocity amplitude ratio of the direct ^-P-and ^-S- waves recorded by regional seismic networks when determining focal mechanism solutions of small earthquakes.
基金funded jointly by China Spark Program of Earthquake Science and Technology(XH12001)Special research fund and Task contract of earthquake trend tracing in 2013 of Beijing Earthquake Administration(2013020109)
文摘Comprehensive statistical analysis was performed on the basic features of focal mechanisms of 619 ML≥2. 0 earthquakes which occurred in the capital circle area from January 2002 to June 2010. By dividing the capital area into three studying regions based on regional tectonic characteristics,cluster analysis was conducted on the focal mechanisms of all subregions using the longest distance method in the statistical cluster analysis to study the characteristics of tectonic stress tensors. The result shows that dominant P-axis azimuth distribution is NNE-NEE and that of T-axis is NNW-NWW,most of the focal areas are controlled by a horizontal stress field and rupture is mainly of horizontal strike-slip. The maximum principal compression stress orientation is NE75° in the west,NE62° in the middle,and near EW in the east of the capital area. The regional tectonic stress field is characterized by horizontal compression.
基金sponsored by the Subject of City ActiveFault Exploration Program of Urumqi and Joint Foundation of Earthquake Administration of Xinjiang Uygur Autonomous Region (200704),China
文摘Using the focal mechanism solutions of 24 moderately strong earthquakes in the northern Tianshan area,we carried out system cluster and stress field inversion analysis.The result indicates that,the focal mechanism solutions of moderately strong earthquakes are mainly dip-slip reverse faulting in the northern Tianshan area.The principal rupture planes of earthquakes are NW-oriented.It is basically consistent with the strike of earthquake structure in its adjacent area.The direction of the principal compression stress P axis is nearly NS,and its inclination angle is small;while the inclination angle of the principal extensional stress T axis is large.It shows that the regional stress field is mainly controlled by the near-NS horizontal compressive stress.The direction of the maximum principal stress shows a gradation process of NNE-NS-NW from east to west.
基金supported by the China Earthquake Administration as a work Assignment for Seismic Situation Tracing for Earthquake Forecast and Prediction (2011020104)
文摘In this article, we have inverted local broadband waveform data to determine the focal mechanism of the 2011 Ms4.8 Anqing earthquake. Our results show that the best double couple solution of the Ms4.8 event is 16°, 74° and 120° for strike, dip and rake angles of one nodal plane respectively, and 131 °, 33°, 30° for the other nodal plane. The estimated focal depth is about 3kin. Both strikes of the two nodal planes differ significantly to the strike of Susong-Zongyang fault, along which seismic activity has been at a low level since the Late Quaternary. This implies that this earthquake may not have occurred on the Susong-Zongyang fault, and we infer that a buried fault with strike of NNE may be the seismogenic structure of this event.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U20A20266 and 12302503)Scientific and technological research projects in Sichuan province(Grant No.2024NSFSC0973).
文摘Source properties and stress fields are critical to understand fundamental mechanisms for fluid-induced earthquakes.In this study,we identify the focal mechanism solutions(FMSs)of 360 earthquakes with local magnitude M_(L)≥1.5 in the Changning shale gas field from January 2016 to May 2017 by fitting three-component waveforms.We then constrain the directions of the maximum horizontal stress(σ_(H_(max)))for four dense earthquake clusters using the stress tensor inversion method.The stress drops of 121 earthquakes with M_(L)≥1.5 are calculated using the spectral ratio method.We examine the spatiotemporal heterogeneity of stress field,and discuss the cause of non-double-couple(non-DC)components in seismicity clusters.Following the Mohr-Coulomb criterion,we estimate the fluid overpressure thresholds from FMS for different seismic clusters,providing insights into potential physical mechanisms for induced seismicity.The FMS results indicate that shallow reverse earthquakes,with steep dip angles,characterize most events.The source mechanisms of earthquakes with M_(L)≥1.5 are dominated by DC components(>70%),but several earthquakes with M_(L)>3.0 and the microseismic events nearby during injection period display significant non-DC components(>30%).Stress inversion results reveal that the σ_(H_(max)) direction ranges from 120°to 128°.Stress drops of earthquakes range between 0.10 and 64.49 MPa,with high values occurring on reverse faults situated at a greater distance from the shale layer,accompanied by a moderate rotation(≤25°)in the trend of σ_(H_(max)).The seismic clusters close to the shale layer exhibit low fluid overpressure thresholds,prone to being triggered by high pore-pressure fluid.The integrated results suggest that the diffusion of high pore pressures is likely to be the primary factor for observed earthquakes.The present results are expected to offer valuable insights into the origin of anomalous seismicity near the shale gas sites.
文摘Objective To study the core contents of the“Implementation Measures for Early Settlement Mechanism of Drug Patent Disputes(Trial)”in China,and to clarify the concerns for enterprises in future work.Methods A comprehensive review of the literature was used to find out the key regulations for detailed decomposition and analysis.Results and Conclusion By analyzing the key clauses of China’s“Implementation Measures for Early Settlement Mechanism of Drug Patent Disputes(Trial)”,some practical countermeasures and suggestions are put forward for related research and development(R&D)innovation and drug declaration of enterprises.
基金supported by National Natural Science Foundation of China[grant numbers 51671168,51871197]National Key Research and Development Program of China[grant number 2017YFA0208200]+1 种基金111 project[grant number B16042]the State Key Program for Basic Research in China[grant no.2015CB6593001]。
文摘Solid solution strengthening is one of the most conventional strategies for optimizing alloys strength,while the corresponding mechanisms can be more complicated than we traditionally thought specifically as heterogeneity of microstructure is involved.In this work,by comparing the change of chemical distribution,dislocation behaviors and mechanical properties after doping equivalent amount of tungsten(W)atoms in CrCoNi alloy and pure Ni,respectively,it is found that the alloying element W in CrCoNi alloy resulted in much stronger strengthening effect due to the significant increase of heterogeneity in chemical distribution after doping trace amount of W.The large atomic scale concentration fluctuation of all elements in CrCoNi-3W causes dislocation motion via strong nanoscale segment detrapping and severe dislocation pile up which is not the case in Ni-3W.The results revealed the high sensitivity of elements distribution in multi-principle element alloys to composition and the significant consequent influence in tuning the mechanical properties,giving insight for complex alloy design.
基金supported by the National Key R/D Project (2016YFC0600301, 2016YFE0109300)the National Natural Science Foundation of China (41574086, 41761134094)China Geological Survey project (DD20160022-05)
文摘The medium-small earthquakes that occurred in the middle part of Tibetan Plateau(32°N–36°N, 90°E–93°E) from August 2016 to June 2017 were relocated using the absolute earthquake location method Hypo2000. Compared to the reports of Chinese Seismological Networks, our relocation results are more clustered on the whole, the horizontal location differences exceed 10 km, and the focal depths are concentrated in 0–8 km, which indicates that the upper crust inside the Tibetan Plateau is tectonically active. In June2017 altogether eight earthquakes above magnitude 3.0 took place; their relocated epicenters are concentrated around Gêladaindong.The relocation results of M<3.0 small earthquakes also showed obvious differences. Therefore, we used the CAP method to invert for the focal mechanisms of the M ≥3.0 earthquakes; results generally tally with the surface geological structures, indicating that the Tibetan Plateau is still under the strong compressional force from the India Plate. Among them the eight earthquakes that occurred near Gêladaindong in June 2017 are all of normal fault type or with some strike-slip at the same time; based on previous research results we conjecture that these events are intense shallow crust responses to deep crust-mantle activities.
基金supported by National Key Basic Research 973bNational Scientific Technology Support Plan (2006BAC01B02-01-01).
文摘Based on abundant aftershock sequence data of the Wenchuan Ms8.0 earthquake on May 12, 2008, we studied the spatio-temporal variation process and segmentation rupture characteristic. Dense aftershocks distribute along Longmenshan central fault zone of NE direction and form a narrow strip with the length of 325 krn and the depth between several and 40 km. The depth profile （section of NW direction） vertical to the strike of aftershock zone （NE direction） shows anisomerous wedgy distribution characteristic of afiershock concentrated regions; it is related to the force form of the Longmenshan nappe tectonic belt. The stronger aftershocks could be divided into northern segment and southern segment apparently and the focal depths of strong aftershocks in the 50 km area between northern segment and southern segment are shallower. It seems like ＇to be going to rupture＇ segment. We also study focal mechanisms and segmentation of strong aftershocks. The principal compressive stress azimuth of aftershock area is WNW direction and the faulting types of aftershocks at southern and northern segment have the same proportion. Because afiershocks distribute on different secondary faults, their focal mechanisms present complex local tectonic stress field. The faulting of seven strong earthquakes on the Longmenshan central fault is mainly characterized by thrust with the component of right-lateral strike-slip. Meantime six strong aftershocks on the Longmenshan back-range fault and Qingchuan fault present strike-slip faulting. At last we discuss the complex segmentation rupture mechanism of the Wenchuan earthquake.
文摘The mechanisms of the February 3, 1996 Lijiang main shock, Yunnan Province, are estimated by using the principle to inverse the mechanisms of two point sources simultaneously. The results are that the main shock of Lijiang consists of two large ruptures, the time difference and the distance between the two ruptures are about 12 s (by the inversion) and about 26 km respectively. An extensional normal with strike-slip fault in about the north-south direction was formed by the first rupture, the mechanism of the second rupture is to be further studied. The method to inverse mechanisms of two point sources at the same time and the results obtained by directly analyzing P waveform records of the main shock are introduced, some related problems are also discussed. The Wuding earthquakes of October, 1995 and the Lijiang earthquake are considered to be the manifestation of the same dynamic process at different temporal and spatial points and the occurrence order of the two earthquakes is related to the direction of dynamics transmission.
基金sponsored by the China Spark Program of Earthquake Science and Technology(XH23051B).
文摘We have developed an automatic regional focal mechanism inversion system based on the Earthquake Rapid Report(ERR) system and the real-time three-component seismic waveform stream of 1 000 broadband seismic stations provided by the China Earthquake Networks Center(CENC). The system can rapidly provide a double couple solution and centroid depth within 5–15 min after receiving earthquake information from the ERR system.The data processing is triggered by earthquake information obtained from the ERR system. The system is capable of determining the focal mechanism of all shallow-depth earthquakes in the Chinese mainland with a magnitude of 5.5–6.5. It utilizes waveform data recorded by seismic stations located within 500 km from the epicenter,enabling the reporting of a focal mechanism solution within 5–15 min of an earthquake occurrence. Additionally,the system can assign a corresponding grade(A B C) to the focal mechanism solution. We processed a total of 301earthquakes that occurred from 2021 to June 2022, and after the quality control, 166 of them were selected.These selected solutions were manually checked, and 160 of them were compiled in a focal mechanism catalog.This catalog can be conveniently downloaded online via the Internet. The automatic focal mechanism solution of earthquakes in eastern China exhibits a good agreement with that provided by the Global Centroid Moment Tensor(GCMT), when available. The average Kagan angle between this catalog and GCMT is 22°, and the average difference in MWis 0.17. Furthermore, compared with GCMT, the minimum magnitude of our catalog has been reduced from approximately 5.0 to 4.0. The correlation between the centroid depth and crustal thickness in the Chinese mainland confirms the distribution of the centroid depth.
基金financially supported by the National Natural Science Foundation of China (No.20471051.)
文摘The solid-phase extraction（SPE） technique applied to the extraction of organic compound was creatively used as the extraction of inorganic gold in the paper.Two types of techniques were proposed and explored,namely the SPE and the liquid–liquid extraction（LLE） of the quaternary ammonium surfactant [cetytrimethyl ammonium bromide（CTMAB）,cetyl pyridine bromide（CPB）,benzyl dimethyl dodecyl ammonium chloride（BDMDAC）,and dodecyl trimethyl ammonium chloride（DTMAC）].The surfactant could react with Au（CN）2^- to form the ionic complex,and the compound could be extracted by SPE column of reversed-phase bonded silica gel.Hence,a new method of SPE was proposed to extract gold with these features of the high selectivity,the reliability,and the simplicity.The experimental result shows that the recovery rate of gold is more than 98 %,and the solid-phase extraction column is not easily damaged and it can be repeatedly used.The new method can be used as the extraction process of gold from alkaline cyanide solution as well.Besides,the paper also puts forward a new process of gold extraction.
