Assessment of strong earthquake risk in the Chinese mainland from 2021 to 2030

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.

Rapid afterslip and short-term viscoelastic relaxation following the 2008 M_W7.9 Wenchuan earthquake

Significant postseismic deformation of the 2008 M W 7.9 Wenchuan earthquake has been observed from GPS data of the first 14 days after the earthquake. The possible mechanisms for the rapid postseismic deformation are assumed to be afterslip on the earthquake rupture plane and viscoelastic relaxation of coseismiclly stress change in the lower crust or upper mantle. We firstly use the constrained least squares method to find an afterslip model which can fit the GPS data best. The afterslip model can explain near-field data very well but shows considerable discrepancies in fitting far-field data. To estimate the effect due to the viscoelastic relaxation in the lower crust, we then ignore the contribution from the afterslip and attempt to invert the viscosity structure beneath the Longmenshan fault where the Wenchuan earthquake occurred from the postseismic deformation data. For this purpose, we use a viscoelastic model with a 2D geometry based on the geological and seismological observations and the coseismic slip distribution derived from the coseismic GPS and InSAR data. By means of a grid search we find that the optimum viscosity is 9×10 18 Pa·s for the middle-lower crust in the Chengdu Basin, 4×10 17 Pa·s for the middle-lower crust in the Chuanxi Plateau and 7×10 17 Pa·s for the low velocity zone in the Chuanxi plateau. The viscoelastic model explains the postseismic deformation observed in the far-field satisfactorily, but it is considerably worse than the afterslip model in fitting the near-fault data. It suggests therefore a hybrid model including both afterslip and relaxation effects. Since the viscoelastic model produces mainly the far-field surface deformation and has fewer degree of freedoms （three viscosity parameters） than the afterslip model with a huge number of source parameters, we fix the viscositiy structure as obtained before but redetermine the afterslip distribution using the residual data from the viscoelastic modeling. The redetermined afterslip distribution becomes physically more reasonable; it is more localized and exhibits a pattern spatially complementary with the coseismic rupture distribution. We conclude that the aseismic fault slip is responsible for the near-fault postseismic deformation, whereas the viscoelastic stress relaxation might be the major cause for the far-field postseismic deformation.

Design and Optimization of Planting Process Parameters for 2ZYX-2 Type Green Onion Ditching and Transplanting Machine

Considering the current low level of mechanization for domestic green onion planting and the high labor intensity of artificial planting,a 2ZYX-2 green onion ditching and transplanting machine,which can complete ditching,ridging,transplanting,repression,soil covering and other operations,is designed in this study.The Central Composite test design method was carried out with the speed of the transplanting machine,the depth of the opener and the horizontal position of the opener as the experimental factors and with the qualification ratio of perpendicularity,the variation coefficient of the plant spacing and the qualification ratio of the planting depth as the test index.Through the analysis of the model interaction and response surface,the change laws that the influence the machine’s forward speed,the depth of the opener and the horizontal position of the opener were studied.The regression model was optimized by Design-Expert 8.0.6 software,and the accuracy of the predicted results was verified by experiments.The optimal working parameters showed that the forward speed of the machine was 0.06 m/s,the depth of the opener was 102 mm,and the horizontal position of the opener was 29 mm.Under conditions of optimal working parameters,the qualification rate of the verticality was 86.83%,the coefficient of variation for the plant spacing was 2.77,and the pass rate of planting depth was 88.26%.The research related to the thesis can provide a reference for the mechanized planting of green onion,which is of great significance to the cost-effectiveness of the green onion industry.

GNSS deformation characteristics of North China in the past two decades

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.

Efficiency-first spraying mission arrangement optimization with multiple UAVs in heterogeneous farmland with varying pesticide requirements

Combining multiple crop protection Unmanned Aerial Vehicles(UAVs)as a team for a scheduled spraying mission over farmland now is a common way to significantly increase efficiency.However,given some issues such as different configurations,irregular borders,and especially varying pesticide requirements,it is more important and more complex than other multi-Agent Systems(MASs)in common use.In this work,we focus on the mission arrangement of UAVs,which is the foundation of other high-level cooperations,systematically propose Efficiency-first Spraying Mission Arrangement Problem(ESMAP),and try to construct a united problem framework for the mission arrangement of crop protection UAVs.Besides,to characterise the differences in sub-areas,the varying pesticide requirement per unit is well considered based on Normalized Difference Vegetation Index(NDVI).Firstly,the mathematical model of multiple crop-protection UAVs is established and ESMAP is defined.Furthermore,an acquisition method of a farmland’s NDVI map is proposed,and the calculation method of pesticide volume based on NDVI is discussed.Secondly,an improved Genetic Algorithm(GA)is proposed to solve ESMAP,and a comparable combination algorithm is introduced.Numerical simulations for algorithm analysis are carried out within MATLAB,and it is determined that the proposed GA is more efficient and accurate than the latter.Finally,a mission arrangement tested with three UAVs was carried out to validate the effectiveness of the proposed GA in spraying operation.Test results illustrated that it performed well,which took only 90.6%of the operation time taken by the combination algorithm.