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Theoretical analysis of ground displacements induced by deep fluid injection based on fully-coupled poroelastic simulation

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Geodesy and Geodynamics 2021年第3期12卷 197-210页

作者： Guoyan Jiang School of Geodesy and Geomatics Wuhan UniversityWuhanChina Earth System Science Programme The Chinese University of Hong KongHong KongChina

Observations of surface displacements are expected to aid in geomechanical analyses of injectioninduced seismicity.However,the controlling factors of the displacement magnitude remain poorly understood except the elastic modulus of the fluid-bearing reservoir.Here,an experiment scheme of numerical simulation based on fully-coupled poroelasticity is designed to investigate the displacements induced by deep underground fluid injection.According to the sealing ability of deep reservoirs,the numerical experiments are classified into two scenarios:injection into open and sealed reservoirs.Potential effects from both geological and operational parameters are considered during the experiments,which include the hydromechanical properties,the reservoir geometry,injection rates and volumes.Experimental results reveal that in addition to the reservoir depth and Young’s modulus,the porosity also has significant influences on the surface displacements.Geodetic modeling of injection-induced displacements should include the parameter of reservoir porosity.When the reservoir is characterized by a good sealing ability,fluid injection is prone to induce larger horizontal displacements than vertical uplifts.Most of injection activities including hydraulic fracturing can probably induce detectable surface displacements.Geodetic surveying,especially using Global Navigation Satellite system(GNSS)with both horizontal and vertical observations,should become an essential monitoring task for anthropogenic fluid injection/production activities,which is conducive to assess and mitigate some geohazards including earthquakes.

关键词： Injection-induced deformation Open and sealed reservoirs Geological and operational parameters Poroelastic simulation Geodetic monitoring

Spatial-temporal evolution of injection-induced earthquakes in the Weiyuan Area determined by machine-learning phase picker and waveform cross-correlation

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earth and Planetary Physics 2021年第6期5卷 485-500页

作者： Wing Ching Jeremy Wong JinPing Zi HongFeng Yang JinRong Su Earth System Science Programme Faculty of ScienceThe Chinese University of Hong KongSha TinHong Kong 999077China earthquake Monitoring Center Sichuan Earthquake AgencyChengdu 610041China

Anthropogenic induced seismicity has been widely reported and investigated in many regions,including the shale gas fields in the Sichuan basin,where the frequency of earthquakes has increased substantially since the commencement of fracking in late 2014.However,the details of how earthquakes are induced remain poorly understood,partly due to lack of high-resolution spatial-temporal data documenting the evolution of such seismic events.Most previous studies have been based on a diffusive earthquake catalog constructed by routine methods.Here,however,we have constructed a high resolution catalog using a machine learning detector and waveform cross-correlation.Despite limited data,this new approach has detected one-third more earthquakes and improves the magnitude completeness of the catalog,illuminating the comprehensive spatial-temporal migration of the emerging seismicity in the target area.One of the clusters clearly delineates a potential unmapped fault trace that may have led to the Mw 5.2 in September 2019,by far the largest earthquake recorded in the region.The migration of the seismicity also demonstrates a pore-pressure diffusion front,suggesting additional constraints on the inducing mechanism of the region.The patterns of the highly clustered seismicity reconcile the causal link between the emerging seismicity and the activity of hydraulic fracturing in the region,facilitating continued investigation of the mechanisms of seismic induction and their associated risks.

关键词： hydraulic fracturing Sichuan Basin machine learning injection-induced earthquake Weiyuan earthquake

An action plan for the agri-food sector at the time of the climate and biodiversity crises

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National science Review 2023年第7期10卷 16-18页

作者： Francesco Cherubini Ting Hua Wenwu Zhao Industrial Ecology programme Department of Energy and Process Engineering Norwegian University of Science and Technology (NTNU) State Key Laboratory of earth Surface Processes and Resource Ecology Faculty of Geographical Science Beijing Normal University Institute of Land Surface system and Sustainable Development Faculty of Geographical Science Beijing Normal University

Land areas on our planet are facing unprecedented levels of stress.More than70%of the global ice-free land has been affected by human activities,30%of the land is threatened by degradation,biodiversity and other ecosystem services(ESs) are declining,and climate change is altering ecosystem functioning [1].Currently,agriculture is the dominant form of land use,with grazing land comprising27%and cropland 12%(and more than half of the cropland is used to produce animal feed).Agriculture is responsible for about one-third of global greenhouse gas(GHG) emissions [2] and it is the primary driver of deforestation,habitat destruction,global freshwater withdrawals,and global ocean and freshwater pollution [3].As land is a limited resource,

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Rapid report of the 8 January 2022 M;6.9 Menyuan earthquake,Qinghai, China

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earthquake Research Advances 2022年

作者： Hongfeng Yang Dun Wang Rumeng Guo Mengyu Xie Yang Zang Yue Wang Qiang Yao Chuang Cheng Yanru An Yingying Zhang Earth System Science Programme Faculty of Science The Chinese University of Hong Kong China University of Geosciences Wuhan State Key Laboratory of Geodesy and earth's Dynamic Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences China earthquake Networks Center China Earthquake Administration

The M;6.9 Menyuan earthquake in Qinghai Province, west China is the largest earthquake by far in 2022. The earthquake occurs in a tectonically active region, with a background b-value of 0.87 within 100 km of the epicenter that we derived from the unified catalog produced by China earthquake Networks Center since late2008. Field surveys have revealed surface ruptures extending 22 km along strike, with a maximum ground displacement of 2.1 m. We construct a finite fault model with constraints from InSAR observations, which showed multiple fault segments during the Menyuan earthquake. The major slip asperity is confined within 10 km at depth, with the maximum slip of 3.5 m. Near real-time back-projection results of coseismic radiation indicate a northwest propagating rupture that lasted for ～10 s. Intensity estimates from the back-projection results show up to a Mercalli scale of IX near the ruptured area, consistent with instrumental measurements and the observations from the field surveys. Aftershock locations（up to January 21, 2022） exhibit two segments, extending to ～20 km in depth. The largest one reaches MS5.3, locating near the eastern end of the aftershock zone. Although the location and the approximate magnitude of the mainshock had been indicated by previous studies based on paleoearthquake records and seismic gap, as well as estimated stressing rate on faults, significant surfacebreaching rupture leads to severe damage of the high-speed railway system, which poses a challenge in accurately assessing earthquake hazards and risks, and thus demands further investigations of the rupture behaviors for crustal earthquakes.

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Deciphering non-steady landscape evolution by in-situ cosmogenic nuclide depth profile

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science China earth sciences 2022年第3期65卷 490-502页

作者： Ye YANG Lifeng CUI Sheng XU Zhenping CAO Shuncheng ZHANG Congqiang LIU Institute of Surface-earth system science School of Earth System ScienceTianjin UniversityTianjin 300072China

In-situ cosmogenic nuclide s are receiving growing attention in surface earth system science in which the steady-state denudation is an important assumption for estimating the surface denudation of long-lived(103-106 years)surfaces.However,distinguishing steady-state denudation and deciphering a reliable denudation rate from non-steady state denudation region are difficult.Recent depth profile models for investigating the denudation rate,exposure age and inheritance are widely used for sediment and regolith of steady-state denudation region.Here we present in-situ co smogenic nuclides^(10)Be and^(26)Al from two typical granite regolithes from Jixian in Tianjin and Tengchong in Yunnan to model non-steady landscape evolution process by using steady state(Model 1)and non-steady state(Model 2,continuous exposure;Model 3 a,changed denudation rate;Model 3 b,abrupt denudation event)models.The results of steady state model show that both regolithes are in non-steady state.^(10)Be non-steady state models of Jixian regolith reveal that the surface has likely experienced a denudation rate change or an abrupt denudation event during the past several millennia,resulting in a non-steady state.The similar Model 3 a and 3 b denudation rates of 14.6-12.9^(+9.4)and 14.7-14.7^(+9.0)mmkyr^(-1),respectively,might demonstrate the long-term denudation rate rather than the exaggerated rate s of 39.0-2.3^(+2.6)and 39.0-2.4+^(2.5)mm kyr^(-1)calculated by assuming steady-state denudation and ignoring inheritance.The non-steady state model results of Tengchong regolith suggest that the surface has likely experienced a strong denudation about 157 ka(^(10)Be)or 127 ka(^(26)Al)ago.This timing is basically consistent with the termination of the MIS 6(TII:130 ka)and the climate change events in the Tibetan Plateau,suggesting a strong surface landscape denudation during the transition from glacial to interglacial.The compiling of basin-wide denudation rates in the Tibetan Plateau shows a good positive correlation with the regional tectonic activi

关键词： Denudation rate Landscape evolution Quaternary geochronology Depth profile Cosmogenic nuclides

Risk assessment and binding mechanisms of potentially toxic metals in sediments from different water levels in a coastal wetland

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Journal of Environmental sciences 2023年第7期129卷 202-212页

作者： Fusheng Sun Guanghui Yu Xingxing Han Zhilai Chi Yunchao Lang Congqiang Liu Institute of Surface-earth system science School of Earth System ScienceTianjin Key Laboratory of Earth Critical Zone Science and Sustainable Development in Bohai RimTianjin UniversityTianjin 300072China

The excessive accumulation of potentially toxic metals(Pb and Cd)in coastal wetlands is among the main factors threateningwetland ecosystems.However,the effects ofwater table depth(WTD)on the risk and binding mechanisms of potentially toxic metals in sediments remain unclear.Here,sediments from different WTD obtained from a typical coastal wetland were evaluated using a newly developed strategy based on chemical extraction methods coupled with high-resolution spectroscopy.Our findings indicated that the WTD of the coastal wetland fluctuates frequently and the average enrichment factor for Pb was categorized as minor,whereas Cd enrichment was categorized as moderate.High-resolution spectroscopy techniques also demonstrated that organic functional groups and partly inorganic compounds(e.g.,Fe-O/Si-O)played a vital role in the binding of Pb and Cd to surface sediments.Additionally,mineral components rather than organic groups were mainly bound to thesemetals in the bottom sediments.Collectively,our findings provide key insights into the potential health effects and binding characteristics of potentially toxic metals in sediments,as well as their dynamic behavior under varying sediment depths at a microscale.

关键词： Coastal wetlands Wetland sediment Toxic metals Risk assessment Synchrotron radiation Binding mechanisms

Shallow crustal velocity structures revealed by active source tomography and fault activities of the Mianning–Xichang segment of the Anninghe fault zone, Southwest China

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earth and Planetary Physics 2022年第2期6卷 204-212页

作者： XiHui Shao HuaJian Yao Ying Liu HongFeng Yang BaoFeng Tian LiHua Fang Laboratory of Seismology and Physics of earth’s Interior School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Mengcheng National Geophysical Observatory University of Science and Technology of ChinaMengcheng Hefei 233500China CAS Center for Excellence in Comparative Planetology University of Science and Technology of ChinaHefei 230026China Earth System Science Programme Faculty of ScienceThe Chinese University of Hong KongHong Kong 999077China Shenzhen Research Institute The Chinese University of Hong KongShenzhen 518057China Institute of Geophysics China Earthquake AdministrationBeijing 100089China

The Anninghe fault is a large left-lateral strike-slip fault in southwestern China. It has controlled deposition and magmatic activities since the Proterozoic, and seismic activity occurs frequently. The Mianning-Xichang segment of the Anninghe fault is a seismic gap that has been locked by high stress. Many studies suggest that this segment has great potential for large earthquakes(magnitude >7). We obtained three vertical velocity profiles of the Anninghe fault(between Mianning and Xichang) based on the inversion of P-wave first arrival times. The travel time data were picked from seismograms generated by methane gaseous sources and recorded by three linearly distributed across-fault dense arrays. The inversion results show that the P-wave velocity structures at depths of 0-2 km corresponds well with the local lithology. The Quaternary sediments have low seismic velocities, whereas the igneous rocks,metamorphic rocks, and bedrock have high seismic velocities. We then further discuss the fault activities of the two fault branches of the Anninghe fault in the study region based on small earthquakes(magnitudes between ML 0.5 and ML 2.5) detected by the Xichang array.The eastern fault branch is more active than the western branch and that the fault activities in the eastern branch are different in the northern and southern segments at the border of 28°21′N. The high-resolution models obtained are essential for future earthquake rupture simulations and hazard assessments of the Anninghe fault zone. Future studies of velocity models at greater depths may further explain the complex fault activities in the study region.

关键词： Anninghe fault zone shallow crust P-wave velocity methane gaseous source fault activity

Investigating the seasonal dynamics of surface water over the Qinghai-Tibet Plateau using Sentinel-1 imagery and a novel gated multiscale ConvNet

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International Journal of Digital earth 2023年第1期16卷 1372-1394页

作者： Xin Luo Zhongwen Hu Lin Liu School of earth sciences Yunnan UniversityKunmingPeople’s Republic of China School of Architecture and Urban Planning Shenzhen UniversityShenzhenPeople’s Republic of China Earth System Science Programme Faculty of ScienceThe Chinese University of Hong KongHong Kong

The surface water in the Qinghai–Tibet Plateau(QTP)region has undergone dramatic changes in recent decades.To capture dynamic surface water information,many satellite imagery-based methods have been proposed.However,these methods are still limited in terms of automation and accuracy and thus prevent surface water dynamic studies in large-scale QTP regions.In this study,we developed a new fully automatic method for accurate surface water mapping by using Sentinel-1 synthetic aperture radar(SAR)imagery and convolutional networks(ConvNets).Specifically,we built a new multiscale ConvNet structure to improve the model capability in surface water body extraction.Moreover,a gating mechanism is introduced to promote the efficient use of multiscale information.According to the accuracy assessment,the proposed gated multiscale ConvNet(GMNet)achieved the highest overall accuracy of 98.07%.We applied our GMNet for monthly surface water mapping on the QTP;accordingly,we found that the QTP region experienced significant surface waterfluctuations over one year.The surface water also showed distinct spatial heterogeneity on the QTP;that is,the surface water fraction of the Inner Tibetan Basin was significantly higher than that of the Mekong Basin in both the wet and dry seasons.

关键词： Qinghai–Tibet Plateau surface water mapping deep learning convolutional neural network SAR image

Effect of varying normal stress on stability and dynamic motion of a spring-slider system with rate- and state-dependent friction

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earthquake science 2014年第6期27卷 577-587页

作者： Changrong He Teng-fong Wong State Key Laboratory of earthquake Dynamics Institute of GeologyCEA Earth System Science Programme Faculty of ScienceThe Chinese University of Hong Kong Department of Geosciences Stony Brook University

Incorporating rate and state friction laws, stability of linearly stable （i.e., with stiffness greater than the critical value） spring-slider systems subjected to triggering perturbations was analyzed under variable normal stress condition, and comparison was made between our results and that of fixed normal stress cases revealed in previous studies. For systems associated with the slip law, the critical mag- nitude of rate steps for triggering unstable slips are found to have a similar pattern to the fixed normal stress case, and the critical velocity steps scale with a/（b - a） when k = kcr for both cases. The rate-step boundaries for the variable normal stress cases are revealed to be lower than the fixed normal stress case by 7 %-16 % for a relatively large ct = 0.56 with （b - a）/a ranging from 0.25 to 1, indicating easier triggering under the variable normal stress condition with rate steps. The difference between fixed and variable normal stress cases decreases when the α value is smaller. In the same slip- law-type systems, critical displacements to trigger instability are revealed to be little affected by the variable normal stress condition. When k 〉 kcr（V,）, a spring-slider system with the slowness law is much more stable than with the slip law,suggesting that the slowness law fits experimental data better when a single state variable is adopted. In stick-slip motions, the variable normal stress case has larger stress drops than the constant normal stress case. The variable normal stress has little effect on the range of slip velocity in systems associated with the slowness law, whereas systems associated with the slip law have a slowest slip velocity immensely smaller than the fixed normal stress case, by ~ 10 orders of magnitude.

关键词： Rate and state friction - Stability Variablenormal stress Stick-slip motion