Quantitative studies on the interseismic and coseismic deformation characteristics and analysis of the interplay between the seismogenic fault and neighboring faults are crucial for understanding the kinematic feature...Quantitative studies on the interseismic and coseismic deformation characteristics and analysis of the interplay between the seismogenic fault and neighboring faults are crucial for understanding the kinematic features and assessing potential seismic hazards. In this study, the interseismic and coseismic deformation of the 2023 Jishishan M_(S)6.2 earthquake(JSSEQ), including the strain rate field, the slip rates,and locking depths of the seismogenic fault during the interseismic period, were obtained. Moreover, the coseismic slip distribution and geometric attributes of the seismogenic fault were further examined.Finally, the potential earthquake hazard in the vicinity was identified by analyzing the Coulomb failure stress changes(ΔCFS). Before the JSSEQ, the maximum shear and dilatational strain rates near the epicenter were significantly lower, and the seismogenic fault was strongly coupled with thrust and dextral strike-slip motion. The maximum displacement of GNSS stations is about 25 mm, about 11 km southwest of the epicenter. The ascending and descending observations reveal a significantly thrustdominated movement, with maximum line of sight displacements of 78 and 83 mm, respectively.Comparing two coseismic slip distribution results and previous studies, it is considered that the east dipping seismogenic fault is more reasonable. The coseismic fault slip took place at a depth of 7.1-13.2 km, with a maximum slip of 0.43 m and a moment magnitude of 6.1. The earthquake resulted in noticeable stress loading on the southeastern end of the Lajishan north margin fault zone and the Lajishan south margin fault zone, as well as the western end of the West Qinling fault zone, which should be given more attention in future.展开更多
Since the 1975 M_(S)7.3 Haicheng earthquake,spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors.Recent technical advances in terrestrial gravity observation...Since the 1975 M_(S)7.3 Haicheng earthquake,spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors.Recent technical advances in terrestrial gravity observation,along with the construction of a high-precision mobile gravity network covering Chinese mainland,have positioned temporal gravity variations(GVs)as an important tool for clarifying the signal characteristics and dynamic mechanisms of crustal sources.Reportedly,crustal mass transfer,which is affected by stress state and structural environment,alters the characteristics of the regional gravity field,thus serving as an indicator for locations of moderate to strong earthquakes and a seismology-independent predictor for regions at risk for strong earthquakes.Therefore,quantitatively tracking time-varying gravity is of paramount importance to enhance the effectiveness of earthquake prediction.In this study,we divided the areas effectively covered by the terrestrial mobile gravity network in the Sichuan-Yunnan region into small grids based on the latest observational data(since 2018)from the network.Next,we calculated the 1-and 3-year GVs and gravity gradient indicators(amplitude of analytic signal,AAS;total horizontal derivative,THD;and amplitude of vertical gradient,AVG)to quantitatively characterize variations in regional time-varying gravity field.Next,we assessed the effectiveness of gravity field variations in predicting earthquakes in the Sichuan-Yunnan region using Molchan diagrams constructed for gravity signals of 13 earthquakes(M≥5.0;occurred between 2021 and 2024)within the terrestrial mobile gravity network.The results reveal a certain correspondence between gravity field variations and the locations of moderate and strong earthquakes in the Sichuan-Yunnan region.Furthermore,the 3-year AAS and AVG outperform the 3-year THD in predicting subsequent seismic events.Notably,the AAS and AVG showed large probability gains prior to the M_(S)6.8 Luding earthquake,indicating their potential for earthquake prediction.展开更多
The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust.These gravity data have many applications,suc...The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust.These gravity data have many applications,such as surface deformation,groundwater storage changes,and mass migration before and after earthquakes.Based on repeated terrestrial gravity measurements at 198 gravity stations in the Sichuan-Yunnan region(SYR)from 2015 to 2017,we determine a time series of degree 120 gravity fields using the localized spherical harmonic(Slepian)basis functions.Our results show that adopting the first 6 Slepian basis functions is sufficient for effective localized Slepian modeling in the SYR.The differences between two gravity campaigns at the same time of year show an obvious correlation with tectonic features.The degree 120 timevariable gravity models presented in this paper will benefit the study of the regional mass migration inside the crust of the SYR and supplement the existing geophysical models for the China Seismic Experimental Site.展开更多
The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland.Based on the strong earthquake recurrence model,the cumulative proba...The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland.Based on the strong earthquake recurrence model,the cumulative probability of each target fault in the next 10 years is given by the recurrence period and elapsed time of each fault,which are adopted from relevant studies such as seismological geology,geodesy,and historical earthquake records.Based on the long-term predictions of large earthquakes throughout the world,this paper proposes a comprehensive judgment scheme based on the fault segments with the seismic gap,motion strongly locked,sparse small-moderate earthquakes,and apparent Coulomb stress increase.This paper presents a comprehensive analysis of the relative risk for strong earthquakes that may occur in the coming 10 years on the major faults in the active tectonic block boundary zones in the Chinese mainland.The present loading rate of each fault is first constrained by geodetic observations;the cumulative displacement of each fault is then estimated by the elapsed time since the most recent strong earthquake.展开更多
The compositions of grain size,clay minerals,and geochemical elements in core sediments(TS4)from the southwestern Taiwan Basin(South China Sea)were investigated to assess the response of terrigenous sediment input to ...The compositions of grain size,clay minerals,and geochemical elements in core sediments(TS4)from the southwestern Taiwan Basin(South China Sea)were investigated to assess the response of terrigenous sediment input to sea level change and the East Asian monsoon evolution since 30 kyr.The chronology was discussed based on foraminiferal AMS14C dates.Our results indi-cated that rivers in Taiwan have been the major sediment contributors since 30 kyr,followed by the Pearl River;and Luzon Island contribute little sediments to the southwestern Taiwan Basin.In this study,we reconstructed the variations in terrigenous sediment input by using the proxies such as Al2O_(3)(%),F1 score,and TiO_(2)/CaO.The F1 score can be used to indicate the flux of terrigenous sediments.The contribution of Taiwan Residents rivers and the Pearl River were evaluated by using the value of(illite+chlorite)/kaolinite.The variations of Al2O_(3)(%),F1 score,and TiO_(2)/CaO values along the core were clearly correlated to the evolution of the East Asian summer monsoon since 30 kyr.Based on these records,we recognized three evolutionary stages of terrigenous sediment input in the southwestern Taiwan Basin.During stage Ⅰ(29-24kyr),the input of terrigenous sediments continued to increase.During stage Ⅱ(24-11.5 kyr),the sediment input decreased at first and then increased,with the lowest value during the last glacial period(21-17kyr).Terrigenous sediment input during stage Ⅲ(11.5 kyr-)showed the decreasing first and then increasing trends,generally higher than those in the first and second stages.The variations of terrigenous sediment input in the study area corresponded well with the evolu-tion of the East Asian summer monsoon since 30 kyr.Increased terrigenous sediment input during 4-1.8 kyr was suggested to be caused by the enhanced ENSO activity.Sea level change does not alter the overall trend of terrigenous sediment input,but does change the relative contributions of rivers in Taiwan and the Pearl River.展开更多
The 2016 MW7.8 Kaikoura earthquake struck the northern part of south Island,New Zealand,within the active and complex Australia-Pacific plate boundary system.Firstly,we used the InSAR method to obtain coseismic LOS de...The 2016 MW7.8 Kaikoura earthquake struck the northern part of south Island,New Zealand,within the active and complex Australia-Pacific plate boundary system.Firstly,we used the InSAR method to obtain coseismic LOS deformation fields based on SAR images and applied offset tracking methods to obtain offset measurements based on optical satellite images.The maximum displacement of about 6 m is detected in the direction away from the satellite on the south-west side and also towards the satellite on the north-east side.The 3D deformation field is then resolved by the combination of these measurements with a least-square solve method,and comparisons with 3 components of GPS stations show good consistency.Despite complex features demonstrated in the 3D deformation field,there are still clear spatial correlations between surface deformation and faults distribution.It reveals that more than ten faults were ruptured during the earthquake,including some faults were previously understudies for their tectonic activities.The maximum horizontal deformation of about 10 m occurs along the Kekerengu fault with the vertical deformation up to 2 m.The 3D deformation shows that the mainshock is a multisegments faulting with a rupture process of strike-slip,compression,transpressional rupture and strike-slip in space along the NE direction.展开更多
Joint inversion is one of the most effective methods for reducing non-uniqueness for geophysical inversion.The current joint inversion methods can be divided into the structural consistency constraint and petrophysica...Joint inversion is one of the most effective methods for reducing non-uniqueness for geophysical inversion.The current joint inversion methods can be divided into the structural consistency constraint and petrophysical consistency constraint methods,which are mutually independent.Currently,there is a need for joint inversion methods that can comprehensively consider the structural consistency constraints and petrophysical consistency constraints.This paper develops the structural similarity index(SSIM)as a new structural and petrophysical consistency constraint for the joint inversion of gravity and vertical gradient data.The SSIM constraint is in the form of a fraction,which may have analytical singularities.Therefore,converting the fractional form to the subtractive form can solve the problem of analytic singularity and finally form a modified structural consistency index of the joint inversion,which enhances the stability of the SSIM constraint applied to the joint inversion.Compared to the reconstructed results from the cross-gradient inversion,the proposed method presents good performance and stability.The SSIM algorithm is a new joint inversion method for petrophysical and structural constraints.It can promote the consistency of the recovered models from the distribution and the structure of the physical property values.Then,applications to synthetic data illustrate that the algorithm proposed in this paper can well process the synthetic data and acquire good reconstructed results.展开更多
We employ the block negative dislocation model to invert the distribution of fault coupling and slip rate deficit on the different segments of the Tanlu(Tancheng-Lujiang) fault zone, according to the GPS horizontal ve...We employ the block negative dislocation model to invert the distribution of fault coupling and slip rate deficit on the different segments of the Tanlu(Tancheng-Lujiang) fault zone, according to the GPS horizontal velocity field from 1991 to 2007(the first phase) and 2013 to 2018(the second phase). By comparing the deformation characteristics results, we discuss the relationship between the deformation characteristics with the M earthquake in Japan. The results showed that the fault coupling rate of the northern section of Tancheng in the second phase reduced compared with that in the first phase. However, the results of the two phases showed that the northern section of Juxian still has a high coupling rate, a deep blocking depth, and a dextral compressive deficit, which is the enrapture section of the 1668 Tancheng earthquake. At the same time, the area strain results show that the strain rate of the central and eastern regions of the second phase is obviously enhanced compared with that of the first phase. The occurrence of the great earthquake in Japan has played a specific role in alleviating the strain accumulation in the middle and south sections of the Tanlu fault zone. The results of the maximum shear strain show that the shear strain in the middle section of the Tanlu fault zone in the second phase is weaker than that in the first phase, and the maximum shear strain in the southern section is stronger than that in the first phase. The fault coupling coefficient of the south Sihong to Jiashan section is high, and it is also the unruptured section of historical earthquakes. At the same time, small earthquakes in this area are not active and accumulate stress easily, so the future earthquake risk deserves attention.展开更多
Based on previous research results,present-day crustal deformation and gravity fields in the Chinese mainland are analyzed using the GPS data,leveling,gravity and cross-fault deformations. We analyzed strain accumulat...Based on previous research results,present-day crustal deformation and gravity fields in the Chinese mainland are analyzed using the GPS data,leveling,gravity and cross-fault deformations. We analyzed strain accumulation of the major faults,and identified locked or high strain accumulation segments. Combining the effects of large earthquakes in the study area,the long-term (decade) probability of large earthquakes in the Chinese mainland is estimated.展开更多
An automatic monitoring method of the 3-D deformation is presented for crustal fault based on laser and machine vision. The laser source and screen are independently set up in the headwall and footwall, the collimated...An automatic monitoring method of the 3-D deformation is presented for crustal fault based on laser and machine vision. The laser source and screen are independently set up in the headwall and footwall, the collimated laser beam creates a circular spot on the screen, meanwhile, the industrial camera captures the tiny deformation of the crustal fault by monitoring the change of the spot position. This method significantly reduces the cost of equipment and labor, provides daily sampling to ensure high continuity of data. A prototype of the automatic monitoring system is developed, and a repeatability test indicates that the error of spot jitter can be minimized by consecutive samples. Meanwhile, the environmental correction model is determined to ensure that environmental changes do not disturb the system. Furthermore, the automatic monitoring system has been applied at the deformation monitoring station(KJX02) of China Beishan underground research laboratory, where continuous deformation monitoring is underway.展开更多
During 7th-15th October 2023,an earthquake sequence with four MW6.2-6.3 occurred in the Herat region,Afghanistan,causing damage to buildings,fire,and loss of life.The co-seismic deformation induced by the earthquake s...During 7th-15th October 2023,an earthquake sequence with four MW6.2-6.3 occurred in the Herat region,Afghanistan,causing damage to buildings,fire,and loss of life.The co-seismic deformation induced by the earthquake sequence helps us invert the rupture model of these earthquakes to constrain the geometric characteristics of the Herat fault system,and estimate the future seismic risk at this fault system.In this work,we utilized the line-of-sight(LOS)displacements from Interferometric Synthetic Aperture Radar(InSAR)observations to determine the optimal fault geometry and slip distribution of the 2023 Afghanistan earthquake sequence through a two-step inversion method.Our results indicated that these four MW6.2-6.3 earthquakes ruptured the western and northwestern segments of the Herat fault system,which are dominated by thrust motions.We identified two fault models from InSAR LOS displacement data,with two different strikes,and the same dip angle range of about 35-45°.The source model with the strike of 280.5°has a peak slip of about 2.2 m,a central rupture zone with about 25 km along-strike length,and a depth range of 5-10 km,corresponding to a MW6.67 earthquake.The following source model with the strike direction of about 240°has smaller rupture length and width,and a peak slip of about 2.5 m,corresponding to a MW6.65 earthquake.We also calculated the Coulomb Failure Stress of the Herat fault system around this rupture area caused by this earthquake sequence.Our results indicated that the stress loading at the western segment of the Herat Fault system is greater than the triggering threshold,suggesting that the future seismic risk in this area is at a relatively high stage.In summary,the rupture model of these earthquakes indicates that two unidentified thrust faults between the western and northwestern segments of the Herat fault system are in a compression-stress environment.展开更多
There are strong interactions between the crust and the mantle in the Abaga area.To study the structure of the crust and upper mantle in that area,the fundamental-mode Rayleigh-wave phase velocity dispersion along 3,3...There are strong interactions between the crust and the mantle in the Abaga area.To study the structure of the crust and upper mantle in that area,the fundamental-mode Rayleigh-wave phase velocity dispersion along 3,331 inter-station paths were estimated by the continuous wavelet transformation method.The dispersion data were used to construct the first 2-D phase velocity maps for waves with periods of 12-80 s and a horizontal resolution of 0.5°×0.5°by applying a linear inversion.The results show that the short-period phase velocity distributions(12-20 s)are affected by exposed Cenozoic volcanoes and the thickness of the sedimentary layer.Phase velocity maps for waves with periods of 30-40 s indicate that the direction of the Solonker suture zone is in good agreement with the extension of the high-speed anomalous connection in the study area.It is concluded that the Solonker suture zone extends throughout the entire lithosphere.For periods of 30-80 s,stable low-velocity anomalies were observed near the Holocene volcanoes in the northeast and south of the study area,suggesting that the low-velocity anomaly is related to volcanic activity.Moreover,the two low-velocity anomalies may be connected,suggesting that the Darigan Volcano may have the same thermal source as the Honggeertu Volcano and even the Datong Volcano.And the thermal source of the two low-velocity anomalies is speculated to be upwelling of hot mantle material.In addition,the velocities in the crust and upper mantle are lower than those from the AK 135 model and are close to the velocity for the destroyed North China Craton,and very similar to that for the East African Rift Valley.This may indicate that the lithospheric structure in the Abaga area is active.展开更多
In this paper, we make a statistical analysis of the fault information of the underground fluid instruments of 12 models in China from January 2021 to May 2022 based on the Pearson correlation coefficient, and compare...In this paper, we make a statistical analysis of the fault information of the underground fluid instruments of 12 models in China from January 2021 to May 2022 based on the Pearson correlation coefficient, and compare the fault statistics of the meteorological three-element instruments of 3 models during the study period. The results show that:(1) The numbers of faults of the underground fluid instruments of 12models with different service times are basically positively correlated with the numbers of the corresponding instruments, with good consistency. Moreover, the automatic observation instruments(8models) with more than 30 units are significantly correlated at a 0.05 significance level(95% confidence level). Even at a 0.01 significance level(99% confidence level), there are 7 models(7/8) with significant correlation.(2) The positive and negative correlations between the monthly average number of faults and the corresponding service times of the underground fluid instruments of 12 models with different service times are random, and there are 9 models(75%) with no significant correlation at a 0.05 significance level(95% confidence level), while 12 models(100%) with no significant correlation at a 0.01significance level(99% confidence level).(3) The monthly average numbers of faults of the underground fluid instruments of 12 models are basically 0.02-0.05 times/(unit·month), and the overall fault frequency is low.(4) The fault statistics results of the meteorological three-element instruments of 3 models are consistent with the characteristics of the underground fluid instruments of 12 models. In general,there is no significant correlation between the fault frequency and the service time of underground fluid instruments.(5) The results of this paper demonstrate that the service time of underground fluid instruments cannot be taken as the main reason for whether to update the instruments. Similarly, the fault frequency of the instruments cannot be taken as the main reason for the service life of the instruments in the process of formulating the service life standards of underground fluid instruments.展开更多
Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The princip...Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The principal conclusions are as follows:1)the GNSS results during 1999-2007 can effectively reflect the deformation characteristics of North China,and the strain rate shows SEE tensile feature in the Shanxi seismic zone with a maximum value of 0.7×10^(-8)/yr.Meanwhile,the deformation is characterized by left-lateral features in the Yinshan seismic zone and Zhangjiakou-Bohai seismic zone with a maximum shear strain rate of 0.7×10^(-8)/yr.2)In the period of 1999-2007,the GNSS velocity profiles show that the deformation is mainly distributed in a range of 100-km width crossing the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai seismic zone,and 50-km width crossing the Zhangjiakou-Bohai seismic zone near the Bohai Bay.3)The deformation response to the 2011 Japan MW9.0 earthquake shows a significant difference between the middle and east sections of the Zhangjiakou-Bohai seismic zone,and the deformation loading rate decreased from 3.3 mm/yr in 1999-2007 to 2.6 mm/yr and 0.9 mm/yr in the 2013-2018 period for above two sections respectively.Furthermore,the fault slip rates inverted from GNSS measurements show a similar dynamic adjustment process,reflecting the weak impact of the Japan MW9.0 earthquake on the deformation around the central section of the Zhangjiakou-Bohai seismic zone.4)From the results of GNSS strain rate,velocity profile and fault slip rate,we suggest that the potential of the strong earthquake should be high in the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai fault zone.展开更多
The gravity and magnetic data can be adopted to interpret the internal structure of the Earth.To improve the calculation efficiency during the inversion process and the accuracy and reliability of the reconstructed ph...The gravity and magnetic data can be adopted to interpret the internal structure of the Earth.To improve the calculation efficiency during the inversion process and the accuracy and reliability of the reconstructed physical property models,the triple strategy is adopted in this paper to develop a fast cross-gradient joint inversion for gravity and magnetic data.The cross-gradient constraint contains solving the gradients of the physical property models and performing the cross-product calculation of their gradients.The sparse matrices are first obtained by calculating the gradients of the physical property models derived from the first-order finite difference.Then,the triple method is applied to optimize the storages and the calculations related to the gradients of the physical property models.Therefore,the storage compression amount of the calculations related to the gradients of the physical property models and the cross-gradient constraint are reduced to one-fold of the number of grid cells at least,and the compression ratio increases with the increase of the number of grid cells.The test results from the synthetic data and field data prove that the structural coupling is achieved by using the fast cross-gradient joint inversion method to effectively reduce the multiplicity of solutions and improve the computing efficiency.展开更多
Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research.In this paper,the temporal and spatial distribution chara...Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research.In this paper,the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method.By analyzing the characteristics of these anomalies,we found that:1)The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau,where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2)The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation,and the migration rate is about 2.4 km/d.The propagation pattern is counterclockwise,consistent with the migration direction of M_(S)≥6.0 earthquakes;3)The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥6.0.Finally,based on the results of gravity field variation and the theory of crust stress wave,the law of deformation anomaly distribution was discussed.We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow.展开更多
In order to study the excitation of large-volume airgun source with different combinations in Hutubi,Xinjiang,China,we conducted a targeted experiment.The method of timefrequency analysis is used to study the signals ...In order to study the excitation of large-volume airgun source with different combinations in Hutubi,Xinjiang,China,we conducted a targeted experiment.The method of timefrequency analysis is used to study the signals recorded by a seismometer on the shore of the excited pool,and it is concluded that different gun combinations will lead to different frequency of bubble pulse signals.Besides,linear combination method is used to analyze the signal-to-noise ratios of signals excited by different gun combinations which was recorded by seismic stations around the airgun source.In order to improve the signal-tonoise ratios,it is more effective to increase the activation energy(the number of excited guns at the same time)than to stack the excited signals with smaller energy repeatedly.展开更多
The paper analyzes the characteristics of the vertical movement of the land in the coastal areas of China and its neighboring areas by using the GNSS observation data of the tide gauge at coastal stations of China and...The paper analyzes the characteristics of the vertical movement of the land in the coastal areas of China and its neighboring areas by using the GNSS observation data of the tide gauge at coastal stations of China and the land-based network GNSS reference stations in the neighboring areas,combined with the satellite altimeter and the sea-level observation data of the stations.The results show that the vertical movement of the land in China's coastal provinces and municipalities and coastal tide gauge stations is generally ascending from Liaoning to Jiangsu Province and subsiding from Shanghai to Quanzhou,Xiamen to Guangxi Autonomous Region coastal alternate pattern of elevation,local coastal plain areas such as southern Tianjin in the North China Plain,and Cang County in the Hebei Plain show significant subsidence characteristics.The uplift and subsidence of land at tide gauge stations is an important part of the relative sea level changes along the coast.The accurate characteristics of the vertical movement of land at tide gauge stations and its adjacent areas provides basis for analysis of relative sea level changes along the coast,assessment of sea level change impact and future sea level rise forecast.展开更多
The Kangdian terrane in the western South China block,having witnessed the Cenozoic continental oblique collision,is one of the few regions globally where orogenic gold and porphyry gold-polymetallic deposits are clos...The Kangdian terrane in the western South China block,having witnessed the Cenozoic continental oblique collision,is one of the few regions globally where orogenic gold and porphyry gold-polymetallic deposits are closely spatially-temporally associated.The control of regional lithospheric evolution on mineralization remains unclear.This study reveals that inherited zircons from the 30.0-24.6 Ma intrusions along the terrane's western boundary,which intruded the Proterozoic igneous rocks,exhibit abundant Proterozoic to Cenozoic ages.This indicates the eastward wedging of the Paleozoic and Mesozoic rocks beneath the Ailaoshan Proterozoic granites,which potentially drove the early Paleogene shearing along the boundary and crustal rotating within the terrane.Orogenic gold deposits derived from metasomatized lithospheric mantle were controlled by largescale shear zones along terrane boundaries.Hydrothermal monazite U-Pb dating and published mineralization ages of orogenic gold deposits demonstrate two mineralization episodes at 52-45 Ma and 30-25 Ma,corresponding to crustal compression and shearing phases during continental collision,respectively.Porphyry gold-polymetallic deposits,coeval with volcanic extensional basins and lamprophyre swarms,formed at ca.35 Ma during the transition from compression to shearing.Paleomagnetic and petrochemical data suggest their formation under crustal rotation within thickened crust.It was revealed that the Cenozoic mafic and felsic rocks in the terrane share similar Nd isotopic compositions,indicating their analogue mantle source from which felsic magma leading to porphyry mineralization was derived.This study demonstrates that mantle devolatilization and shearing along terrane boundaries generated orogenic gold mineralization during stress relaxation,while the evolution of mantle-derived magmatic systems associated with crustal rotation within the terrane governed porphyry gold-polymetallic mineralization during the tectonic transition.展开更多
On January 1,2024,a devastating M 7.6 earthquake struck the Noto Peninsula,Ishikawa Prefecture,Japan,resulting in significant casualties and property damage.Utilizing information from the first six days after the eart...On January 1,2024,a devastating M 7.6 earthquake struck the Noto Peninsula,Ishikawa Prefecture,Japan,resulting in significant casualties and property damage.Utilizing information from the first six days after the earthquake,this article analyzes the seismic source characteristics,disaster situation,and emergency response of this earthquake.The results show:1)The earthquake rupture was of the thrust type,with aftershock distribution showing a north-east-oriented belt-like feature of 150 km.2)Global Navigation Satellite System(GNSS)and Interferometric synthetic aperture radar(InSAR),observations detected significant westward to north-westward co-seismic displacement near the epicenter,with the maximum horizontal displacement reaching 1.2 m and the vertical uplift displacement reaching 4 m.A two-segment fault inversion model fits the observational data well.3)Near the epicenter,large Peak Ground Velocity(PGV)and Peak Ground Acceleration(PGA)were observed,with the maxima reaching 145 cm/s and 2681 gal,respectively,and the intensity reached the highest level 7 on the Japanese(Japan Meteorological Agency,JMA)intensity standard,which is higher than level 10 of the United States Geological Survey(USGS)Modified Mercalli Intensity(MMI)standard.4)The observation of the very rare multiple strong pulse-like ground motion(PLGM)waveform poses a topic worthy of research in the field of earthquake engineering.5)As of January 7,the earthquake had left 128 deaths and 560 injuries in Ishikawa Prefecture,with 1305 buildings completely or partially destroyed,and had triggered a chain of disasters including tsunamis,fires,slope failures,and road damage.Finally,this paper summarizes the emergency rescue,information dissemination,and other disaster response and management measures taken in response to this earthquake.This work provides a reference case for carrying out effective responses,and offers lessons for handling similar events in the future.展开更多
基金funded by the National Natural Science Foundation of China (Grant No. 42204008)the National Key Research and Development Program of China (No. 2022YFC3003703)the Scientific Research Project Coordinating Fund of the First Monitoring and Application Center, China Earthquake Administration (No. FMC2022014)
文摘Quantitative studies on the interseismic and coseismic deformation characteristics and analysis of the interplay between the seismogenic fault and neighboring faults are crucial for understanding the kinematic features and assessing potential seismic hazards. In this study, the interseismic and coseismic deformation of the 2023 Jishishan M_(S)6.2 earthquake(JSSEQ), including the strain rate field, the slip rates,and locking depths of the seismogenic fault during the interseismic period, were obtained. Moreover, the coseismic slip distribution and geometric attributes of the seismogenic fault were further examined.Finally, the potential earthquake hazard in the vicinity was identified by analyzing the Coulomb failure stress changes(ΔCFS). Before the JSSEQ, the maximum shear and dilatational strain rates near the epicenter were significantly lower, and the seismogenic fault was strongly coupled with thrust and dextral strike-slip motion. The maximum displacement of GNSS stations is about 25 mm, about 11 km southwest of the epicenter. The ascending and descending observations reveal a significantly thrustdominated movement, with maximum line of sight displacements of 78 and 83 mm, respectively.Comparing two coseismic slip distribution results and previous studies, it is considered that the east dipping seismogenic fault is more reasonable. The coseismic fault slip took place at a depth of 7.1-13.2 km, with a maximum slip of 0.43 m and a moment magnitude of 6.1. The earthquake resulted in noticeable stress loading on the southeastern end of the Lajishan north margin fault zone and the Lajishan south margin fault zone, as well as the western end of the West Qinling fault zone, which should be given more attention in future.
基金funded by the National Key R&D Program of China(Nos.2023YFE0101800 and 2023YFC 3007305)National Natural Science Foundation of China(Nos.42004069 and 42204093)Special Fund of the Institute of Geophysics,China Earthquake Administration(No.DQJB24X24).
文摘Since the 1975 M_(S)7.3 Haicheng earthquake,spatio-temporal variations in the gravity field have attracted much attention as potential earthquake precursors.Recent technical advances in terrestrial gravity observation,along with the construction of a high-precision mobile gravity network covering Chinese mainland,have positioned temporal gravity variations(GVs)as an important tool for clarifying the signal characteristics and dynamic mechanisms of crustal sources.Reportedly,crustal mass transfer,which is affected by stress state and structural environment,alters the characteristics of the regional gravity field,thus serving as an indicator for locations of moderate to strong earthquakes and a seismology-independent predictor for regions at risk for strong earthquakes.Therefore,quantitatively tracking time-varying gravity is of paramount importance to enhance the effectiveness of earthquake prediction.In this study,we divided the areas effectively covered by the terrestrial mobile gravity network in the Sichuan-Yunnan region into small grids based on the latest observational data(since 2018)from the network.Next,we calculated the 1-and 3-year GVs and gravity gradient indicators(amplitude of analytic signal,AAS;total horizontal derivative,THD;and amplitude of vertical gradient,AVG)to quantitatively characterize variations in regional time-varying gravity field.Next,we assessed the effectiveness of gravity field variations in predicting earthquakes in the Sichuan-Yunnan region using Molchan diagrams constructed for gravity signals of 13 earthquakes(M≥5.0;occurred between 2021 and 2024)within the terrestrial mobile gravity network.The results reveal a certain correspondence between gravity field variations and the locations of moderate and strong earthquakes in the Sichuan-Yunnan region.Furthermore,the 3-year AAS and AVG outperform the 3-year THD in predicting subsequent seismic events.Notably,the AAS and AVG showed large probability gains prior to the M_(S)6.8 Luding earthquake,indicating their potential for earthquake prediction.
基金the National Natural Science Foundation of China(Nos.41974095,41774090,and U1939205)the Special Fund of the Institute of Geophysics,China Earthquake Administration(Nos.DQJB20X09,and DQJB21R30)The first author acknowledges support from the China Postdoctoral Science Foundation(No.2018M641424)。
文摘The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust.These gravity data have many applications,such as surface deformation,groundwater storage changes,and mass migration before and after earthquakes.Based on repeated terrestrial gravity measurements at 198 gravity stations in the Sichuan-Yunnan region(SYR)from 2015 to 2017,we determine a time series of degree 120 gravity fields using the localized spherical harmonic(Slepian)basis functions.Our results show that adopting the first 6 Slepian basis functions is sufficient for effective localized Slepian modeling in the SYR.The differences between two gravity campaigns at the same time of year show an obvious correlation with tectonic features.The degree 120 timevariable gravity models presented in this paper will benefit the study of the regional mass migration inside the crust of the SYR and supplement the existing geophysical models for the China Seismic Experimental Site.
基金the National Key R&D Program of China(grants 2017YFC1500501).
文摘The long-term earthquake prediction from 2021 to 2030 is carried out by researching the active tectonic block boundary zones in the Chinese mainland.Based on the strong earthquake recurrence model,the cumulative probability of each target fault in the next 10 years is given by the recurrence period and elapsed time of each fault,which are adopted from relevant studies such as seismological geology,geodesy,and historical earthquake records.Based on the long-term predictions of large earthquakes throughout the world,this paper proposes a comprehensive judgment scheme based on the fault segments with the seismic gap,motion strongly locked,sparse small-moderate earthquakes,and apparent Coulomb stress increase.This paper presents a comprehensive analysis of the relative risk for strong earthquakes that may occur in the coming 10 years on the major faults in the active tectonic block boundary zones in the Chinese mainland.The present loading rate of each fault is first constrained by geodetic observations;the cumulative displacement of each fault is then estimated by the elapsed time since the most recent strong earthquake.
基金This study was financially supported by the National Key Research and Development Program(No.2017YFC 0306703)the National Natural Science Foundation of China(No.41706065).
文摘The compositions of grain size,clay minerals,and geochemical elements in core sediments(TS4)from the southwestern Taiwan Basin(South China Sea)were investigated to assess the response of terrigenous sediment input to sea level change and the East Asian monsoon evolution since 30 kyr.The chronology was discussed based on foraminiferal AMS14C dates.Our results indi-cated that rivers in Taiwan have been the major sediment contributors since 30 kyr,followed by the Pearl River;and Luzon Island contribute little sediments to the southwestern Taiwan Basin.In this study,we reconstructed the variations in terrigenous sediment input by using the proxies such as Al2O_(3)(%),F1 score,and TiO_(2)/CaO.The F1 score can be used to indicate the flux of terrigenous sediments.The contribution of Taiwan Residents rivers and the Pearl River were evaluated by using the value of(illite+chlorite)/kaolinite.The variations of Al2O_(3)(%),F1 score,and TiO_(2)/CaO values along the core were clearly correlated to the evolution of the East Asian summer monsoon since 30 kyr.Based on these records,we recognized three evolutionary stages of terrigenous sediment input in the southwestern Taiwan Basin.During stage Ⅰ(29-24kyr),the input of terrigenous sediments continued to increase.During stage Ⅱ(24-11.5 kyr),the sediment input decreased at first and then increased,with the lowest value during the last glacial period(21-17kyr).Terrigenous sediment input during stage Ⅲ(11.5 kyr-)showed the decreasing first and then increasing trends,generally higher than those in the first and second stages.The variations of terrigenous sediment input in the study area corresponded well with the evolu-tion of the East Asian summer monsoon since 30 kyr.Increased terrigenous sediment input during 4-1.8 kyr was suggested to be caused by the enhanced ENSO activity.Sea level change does not alter the overall trend of terrigenous sediment input,but does change the relative contributions of rivers in Taiwan and the Pearl River.
基金co-supported by the National Key Research and Development Program of China(Grant No.2019YFC1509204)the National Nonprofit Fundamental Research Grant of China,Institute of Geology,China Earthquake Administration(Grant No.IGCEA2005 and No.IGCEA2014)the National Science Foundation of China(Grant No.41631073)
文摘The 2016 MW7.8 Kaikoura earthquake struck the northern part of south Island,New Zealand,within the active and complex Australia-Pacific plate boundary system.Firstly,we used the InSAR method to obtain coseismic LOS deformation fields based on SAR images and applied offset tracking methods to obtain offset measurements based on optical satellite images.The maximum displacement of about 6 m is detected in the direction away from the satellite on the south-west side and also towards the satellite on the north-east side.The 3D deformation field is then resolved by the combination of these measurements with a least-square solve method,and comparisons with 3 components of GPS stations show good consistency.Despite complex features demonstrated in the 3D deformation field,there are still clear spatial correlations between surface deformation and faults distribution.It reveals that more than ten faults were ruptured during the earthquake,including some faults were previously understudies for their tectonic activities.The maximum horizontal deformation of about 10 m occurs along the Kekerengu fault with the vertical deformation up to 2 m.The 3D deformation shows that the mainshock is a multisegments faulting with a rupture process of strike-slip,compression,transpressional rupture and strike-slip in space along the NE direction.
基金supported by the National Key Research and Development Program(Grant No.2021YFA0716100)the National Key Research and Development Program of China Project(Grant No.2018YFC0603502)+1 种基金the Henan Youth Science Fund Program(Grant No.212300410105)the provincial key R&D and promotion special project of Henan Province(Grant No.222102320279).
文摘Joint inversion is one of the most effective methods for reducing non-uniqueness for geophysical inversion.The current joint inversion methods can be divided into the structural consistency constraint and petrophysical consistency constraint methods,which are mutually independent.Currently,there is a need for joint inversion methods that can comprehensively consider the structural consistency constraints and petrophysical consistency constraints.This paper develops the structural similarity index(SSIM)as a new structural and petrophysical consistency constraint for the joint inversion of gravity and vertical gradient data.The SSIM constraint is in the form of a fraction,which may have analytical singularities.Therefore,converting the fractional form to the subtractive form can solve the problem of analytic singularity and finally form a modified structural consistency index of the joint inversion,which enhances the stability of the SSIM constraint applied to the joint inversion.Compared to the reconstructed results from the cross-gradient inversion,the proposed method presents good performance and stability.The SSIM algorithm is a new joint inversion method for petrophysical and structural constraints.It can promote the consistency of the recovered models from the distribution and the structure of the physical property values.Then,applications to synthetic data illustrate that the algorithm proposed in this paper can well process the synthetic data and acquire good reconstructed results.
基金supported by the National Natural Science Foundation of China (Grand number 41802224)the Youth Program of Seismological Science and Technology Spark Program of China Earthquake Administration (Grand No. XH23019YC)the Joint Open Fund of National Geophysical Observation and Research Station in Mengcheng, Anhui Province (Grand No. MENGO-202114)。
文摘We employ the block negative dislocation model to invert the distribution of fault coupling and slip rate deficit on the different segments of the Tanlu(Tancheng-Lujiang) fault zone, according to the GPS horizontal velocity field from 1991 to 2007(the first phase) and 2013 to 2018(the second phase). By comparing the deformation characteristics results, we discuss the relationship between the deformation characteristics with the M earthquake in Japan. The results showed that the fault coupling rate of the northern section of Tancheng in the second phase reduced compared with that in the first phase. However, the results of the two phases showed that the northern section of Juxian still has a high coupling rate, a deep blocking depth, and a dextral compressive deficit, which is the enrapture section of the 1668 Tancheng earthquake. At the same time, the area strain results show that the strain rate of the central and eastern regions of the second phase is obviously enhanced compared with that of the first phase. The occurrence of the great earthquake in Japan has played a specific role in alleviating the strain accumulation in the middle and south sections of the Tanlu fault zone. The results of the maximum shear strain show that the shear strain in the middle section of the Tanlu fault zone in the second phase is weaker than that in the first phase, and the maximum shear strain in the southern section is stronger than that in the first phase. The fault coupling coefficient of the south Sihong to Jiashan section is high, and it is also the unruptured section of historical earthquakes. At the same time, small earthquakes in this area are not active and accumulate stress easily, so the future earthquake risk deserves attention.
基金sponsored by the Special Fund for Earthquake Scientific Research of ERC
文摘Based on previous research results,present-day crustal deformation and gravity fields in the Chinese mainland are analyzed using the GPS data,leveling,gravity and cross-fault deformations. We analyzed strain accumulation of the major faults,and identified locked or high strain accumulation segments. Combining the effects of large earthquakes in the study area,the long-term (decade) probability of large earthquakes in the Chinese mainland is estimated.
基金supported by Earthquake Sciences Spark Programs of China Earthquake Administration(No.XH22020YA)Science Innovation Fund granted by the First Monitoring and Application Center of China Earthquake Administration(No.FMC202309).
文摘An automatic monitoring method of the 3-D deformation is presented for crustal fault based on laser and machine vision. The laser source and screen are independently set up in the headwall and footwall, the collimated laser beam creates a circular spot on the screen, meanwhile, the industrial camera captures the tiny deformation of the crustal fault by monitoring the change of the spot position. This method significantly reduces the cost of equipment and labor, provides daily sampling to ensure high continuity of data. A prototype of the automatic monitoring system is developed, and a repeatability test indicates that the error of spot jitter can be minimized by consecutive samples. Meanwhile, the environmental correction model is determined to ensure that environmental changes do not disturb the system. Furthermore, the automatic monitoring system has been applied at the deformation monitoring station(KJX02) of China Beishan underground research laboratory, where continuous deformation monitoring is underway.
基金funded by the PhD Starting Research Fund in East China Jiaotong University,Grant No.2003423017the National Natural Science Foundation of China(Grant Nos.42304009)。
文摘During 7th-15th October 2023,an earthquake sequence with four MW6.2-6.3 occurred in the Herat region,Afghanistan,causing damage to buildings,fire,and loss of life.The co-seismic deformation induced by the earthquake sequence helps us invert the rupture model of these earthquakes to constrain the geometric characteristics of the Herat fault system,and estimate the future seismic risk at this fault system.In this work,we utilized the line-of-sight(LOS)displacements from Interferometric Synthetic Aperture Radar(InSAR)observations to determine the optimal fault geometry and slip distribution of the 2023 Afghanistan earthquake sequence through a two-step inversion method.Our results indicated that these four MW6.2-6.3 earthquakes ruptured the western and northwestern segments of the Herat fault system,which are dominated by thrust motions.We identified two fault models from InSAR LOS displacement data,with two different strikes,and the same dip angle range of about 35-45°.The source model with the strike of 280.5°has a peak slip of about 2.2 m,a central rupture zone with about 25 km along-strike length,and a depth range of 5-10 km,corresponding to a MW6.67 earthquake.The following source model with the strike direction of about 240°has smaller rupture length and width,and a peak slip of about 2.5 m,corresponding to a MW6.65 earthquake.We also calculated the Coulomb Failure Stress of the Herat fault system around this rupture area caused by this earthquake sequence.Our results indicated that the stress loading at the western segment of the Herat Fault system is greater than the triggering threshold,suggesting that the future seismic risk in this area is at a relatively high stage.In summary,the rupture model of these earthquakes indicates that two unidentified thrust faults between the western and northwestern segments of the Herat fault system are in a compression-stress environment.
基金National Natural Science Foundation of China(Nos.41674094 and 41504073)。
文摘There are strong interactions between the crust and the mantle in the Abaga area.To study the structure of the crust and upper mantle in that area,the fundamental-mode Rayleigh-wave phase velocity dispersion along 3,331 inter-station paths were estimated by the continuous wavelet transformation method.The dispersion data were used to construct the first 2-D phase velocity maps for waves with periods of 12-80 s and a horizontal resolution of 0.5°×0.5°by applying a linear inversion.The results show that the short-period phase velocity distributions(12-20 s)are affected by exposed Cenozoic volcanoes and the thickness of the sedimentary layer.Phase velocity maps for waves with periods of 30-40 s indicate that the direction of the Solonker suture zone is in good agreement with the extension of the high-speed anomalous connection in the study area.It is concluded that the Solonker suture zone extends throughout the entire lithosphere.For periods of 30-80 s,stable low-velocity anomalies were observed near the Holocene volcanoes in the northeast and south of the study area,suggesting that the low-velocity anomaly is related to volcanic activity.Moreover,the two low-velocity anomalies may be connected,suggesting that the Darigan Volcano may have the same thermal source as the Honggeertu Volcano and even the Datong Volcano.And the thermal source of the two low-velocity anomalies is speculated to be upwelling of hot mantle material.In addition,the velocities in the crust and upper mantle are lower than those from the AK 135 model and are close to the velocity for the destroyed North China Craton,and very similar to that for the East African Rift Valley.This may indicate that the lithospheric structure in the Abaga area is active.
基金supported by the Science Project for Earthquake Resilience of China Earthquake Administration(XH22020YA).
文摘In this paper, we make a statistical analysis of the fault information of the underground fluid instruments of 12 models in China from January 2021 to May 2022 based on the Pearson correlation coefficient, and compare the fault statistics of the meteorological three-element instruments of 3 models during the study period. The results show that:(1) The numbers of faults of the underground fluid instruments of 12models with different service times are basically positively correlated with the numbers of the corresponding instruments, with good consistency. Moreover, the automatic observation instruments(8models) with more than 30 units are significantly correlated at a 0.05 significance level(95% confidence level). Even at a 0.01 significance level(99% confidence level), there are 7 models(7/8) with significant correlation.(2) The positive and negative correlations between the monthly average number of faults and the corresponding service times of the underground fluid instruments of 12 models with different service times are random, and there are 9 models(75%) with no significant correlation at a 0.05 significance level(95% confidence level), while 12 models(100%) with no significant correlation at a 0.01significance level(99% confidence level).(3) The monthly average numbers of faults of the underground fluid instruments of 12 models are basically 0.02-0.05 times/(unit·month), and the overall fault frequency is low.(4) The fault statistics results of the meteorological three-element instruments of 3 models are consistent with the characteristics of the underground fluid instruments of 12 models. In general,there is no significant correlation between the fault frequency and the service time of underground fluid instruments.(5) The results of this paper demonstrate that the service time of underground fluid instruments cannot be taken as the main reason for whether to update the instruments. Similarly, the fault frequency of the instruments cannot be taken as the main reason for the service life of the instruments in the process of formulating the service life standards of underground fluid instruments.
基金financially supported by the National Science Foundation of China(41974011)funded by the National Key R&D Program of China[2018YFC1503606]。
文摘Based on the Global Navigation Satellite System(GNSS)velocity in North China from 1999 to 2018,the deformation parameters,such as the strain rate,the velocity profiles,and the fault slip rates,are analyzed.The principal conclusions are as follows:1)the GNSS results during 1999-2007 can effectively reflect the deformation characteristics of North China,and the strain rate shows SEE tensile feature in the Shanxi seismic zone with a maximum value of 0.7×10^(-8)/yr.Meanwhile,the deformation is characterized by left-lateral features in the Yinshan seismic zone and Zhangjiakou-Bohai seismic zone with a maximum shear strain rate of 0.7×10^(-8)/yr.2)In the period of 1999-2007,the GNSS velocity profiles show that the deformation is mainly distributed in a range of 100-km width crossing the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai seismic zone,and 50-km width crossing the Zhangjiakou-Bohai seismic zone near the Bohai Bay.3)The deformation response to the 2011 Japan MW9.0 earthquake shows a significant difference between the middle and east sections of the Zhangjiakou-Bohai seismic zone,and the deformation loading rate decreased from 3.3 mm/yr in 1999-2007 to 2.6 mm/yr and 0.9 mm/yr in the 2013-2018 period for above two sections respectively.Furthermore,the fault slip rates inverted from GNSS measurements show a similar dynamic adjustment process,reflecting the weak impact of the Japan MW9.0 earthquake on the deformation around the central section of the Zhangjiakou-Bohai seismic zone.4)From the results of GNSS strain rate,velocity profile and fault slip rate,we suggest that the potential of the strong earthquake should be high in the Yinshan seismic zone and the middle section of the Zhangjiakou-Bohai fault zone.
基金supported by the National Key Research and Development Program(Grant No.2021YFA0716100)the National Key Research and Development Program of China Project(Grant No.2018YFC0603502)Henan Youth Science Fund Program(Grant No.212300410105).
文摘The gravity and magnetic data can be adopted to interpret the internal structure of the Earth.To improve the calculation efficiency during the inversion process and the accuracy and reliability of the reconstructed physical property models,the triple strategy is adopted in this paper to develop a fast cross-gradient joint inversion for gravity and magnetic data.The cross-gradient constraint contains solving the gradients of the physical property models and performing the cross-product calculation of their gradients.The sparse matrices are first obtained by calculating the gradients of the physical property models derived from the first-order finite difference.Then,the triple method is applied to optimize the storages and the calculations related to the gradients of the physical property models.Therefore,the storage compression amount of the calculations related to the gradients of the physical property models and the cross-gradient constraint are reduced to one-fold of the number of grid cells at least,and the compression ratio increases with the increase of the number of grid cells.The test results from the synthetic data and field data prove that the structural coupling is achieved by using the fast cross-gradient joint inversion method to effectively reduce the multiplicity of solutions and improve the computing efficiency.
基金sponsored by the National Natural Science Foundation of China(41330314)。
文摘Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research.In this paper,the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method.By analyzing the characteristics of these anomalies,we found that:1)The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau,where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2)The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation,and the migration rate is about 2.4 km/d.The propagation pattern is counterclockwise,consistent with the migration direction of M_(S)≥6.0 earthquakes;3)The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥6.0.Finally,based on the results of gravity field variation and the theory of crust stress wave,the law of deformation anomaly distribution was discussed.We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow.
基金the National Key R&D Program of China(2018YFC1503200)the National Natural Science Foundation of China(41474051)Earthquake Science Foundation of Xinjiang(201902)
文摘In order to study the excitation of large-volume airgun source with different combinations in Hutubi,Xinjiang,China,we conducted a targeted experiment.The method of timefrequency analysis is used to study the signals recorded by a seismometer on the shore of the excited pool,and it is concluded that different gun combinations will lead to different frequency of bubble pulse signals.Besides,linear combination method is used to analyze the signal-to-noise ratios of signals excited by different gun combinations which was recorded by seismic stations around the airgun source.In order to improve the signal-tonoise ratios,it is more effective to increase the activation energy(the number of excited guns at the same time)than to stack the excited signals with smaller energy repeatedly.
文摘The paper analyzes the characteristics of the vertical movement of the land in the coastal areas of China and its neighboring areas by using the GNSS observation data of the tide gauge at coastal stations of China and the land-based network GNSS reference stations in the neighboring areas,combined with the satellite altimeter and the sea-level observation data of the stations.The results show that the vertical movement of the land in China's coastal provinces and municipalities and coastal tide gauge stations is generally ascending from Liaoning to Jiangsu Province and subsiding from Shanghai to Quanzhou,Xiamen to Guangxi Autonomous Region coastal alternate pattern of elevation,local coastal plain areas such as southern Tianjin in the North China Plain,and Cang County in the Hebei Plain show significant subsidence characteristics.The uplift and subsidence of land at tide gauge stations is an important part of the relative sea level changes along the coast.The accurate characteristics of the vertical movement of land at tide gauge stations and its adjacent areas provides basis for analysis of relative sea level changes along the coast,assessment of sea level change impact and future sea level rise forecast.
基金supported by the National Natural Science Foundation of China(Grant No.42125203)the 111 Project of China(Grant No.BP0719021)。
文摘The Kangdian terrane in the western South China block,having witnessed the Cenozoic continental oblique collision,is one of the few regions globally where orogenic gold and porphyry gold-polymetallic deposits are closely spatially-temporally associated.The control of regional lithospheric evolution on mineralization remains unclear.This study reveals that inherited zircons from the 30.0-24.6 Ma intrusions along the terrane's western boundary,which intruded the Proterozoic igneous rocks,exhibit abundant Proterozoic to Cenozoic ages.This indicates the eastward wedging of the Paleozoic and Mesozoic rocks beneath the Ailaoshan Proterozoic granites,which potentially drove the early Paleogene shearing along the boundary and crustal rotating within the terrane.Orogenic gold deposits derived from metasomatized lithospheric mantle were controlled by largescale shear zones along terrane boundaries.Hydrothermal monazite U-Pb dating and published mineralization ages of orogenic gold deposits demonstrate two mineralization episodes at 52-45 Ma and 30-25 Ma,corresponding to crustal compression and shearing phases during continental collision,respectively.Porphyry gold-polymetallic deposits,coeval with volcanic extensional basins and lamprophyre swarms,formed at ca.35 Ma during the transition from compression to shearing.Paleomagnetic and petrochemical data suggest their formation under crustal rotation within thickened crust.It was revealed that the Cenozoic mafic and felsic rocks in the terrane share similar Nd isotopic compositions,indicating their analogue mantle source from which felsic magma leading to porphyry mineralization was derived.This study demonstrates that mantle devolatilization and shearing along terrane boundaries generated orogenic gold mineralization during stress relaxation,while the evolution of mantle-derived magmatic systems associated with crustal rotation within the terrane governed porphyry gold-polymetallic mineralization during the tectonic transition.
基金supported by National High-level Innovative Talents Scientific Research Project in Hebei Province,China(No.405492)JSPS KAKENHI(No.JP19KK0121)National Natural Science Foundation of China(Grant No.42207224).
文摘On January 1,2024,a devastating M 7.6 earthquake struck the Noto Peninsula,Ishikawa Prefecture,Japan,resulting in significant casualties and property damage.Utilizing information from the first six days after the earthquake,this article analyzes the seismic source characteristics,disaster situation,and emergency response of this earthquake.The results show:1)The earthquake rupture was of the thrust type,with aftershock distribution showing a north-east-oriented belt-like feature of 150 km.2)Global Navigation Satellite System(GNSS)and Interferometric synthetic aperture radar(InSAR),observations detected significant westward to north-westward co-seismic displacement near the epicenter,with the maximum horizontal displacement reaching 1.2 m and the vertical uplift displacement reaching 4 m.A two-segment fault inversion model fits the observational data well.3)Near the epicenter,large Peak Ground Velocity(PGV)and Peak Ground Acceleration(PGA)were observed,with the maxima reaching 145 cm/s and 2681 gal,respectively,and the intensity reached the highest level 7 on the Japanese(Japan Meteorological Agency,JMA)intensity standard,which is higher than level 10 of the United States Geological Survey(USGS)Modified Mercalli Intensity(MMI)standard.4)The observation of the very rare multiple strong pulse-like ground motion(PLGM)waveform poses a topic worthy of research in the field of earthquake engineering.5)As of January 7,the earthquake had left 128 deaths and 560 injuries in Ishikawa Prefecture,with 1305 buildings completely or partially destroyed,and had triggered a chain of disasters including tsunamis,fires,slope failures,and road damage.Finally,this paper summarizes the emergency rescue,information dissemination,and other disaster response and management measures taken in response to this earthquake.This work provides a reference case for carrying out effective responses,and offers lessons for handling similar events in the future.
