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The deformation response models of earthquake cycle play a crucial role in studying the entire dynamic process of earthquakes, from inception, nucleation and rupture, to postseismic adjustments, as well as in exploring the rheological properties of Earth' s crust and mantle. They have significant implications in earthquake prediction, forecasting, seismic hazard mitigation and risk assessment. First, this paper introduces the characteristics of deformation during the interseismic phase of the earthquake cycle. It categorizes and summarizes the corresponding models from the perspectives of dimensionality and elastic-visc-oelastic models, and it elaborates on the characteristics, limitations and historical evolution of simulation methods for coseismic deformation, with a particular focus on mainstream approaches for determining the geometry of coseismic faults and selecting smoothing schemes. Then, this paper discusses the spatiotemporal evolution features of postseismic deformation, and categorizes them according to deformation mechanisms, including poroelastic rebound, viscoelastic relaxation and postseismic afterslip. It also outlines the characteristics and limitations of simulation methods for deformation phenomena and provides a classification summary of current mainstream postseismic combined models. Furthermore, this paper explores the opportunities and challenges faced by earthquake cycle deformation simulation methods in the rapidly accumulating data environment. It emphasizes the importance of three-dimensional viscoelastic models, considering the viscoelastic relaxation effects of Earth's crust and mantle. Finally, this paper offers prospects for future research directions, including single-fault earthquake cycle deformation simulation, postseismic mechanisms, dynamic modeling and interpretation of possible earthquake cycle deformation phenomena. [ABSTRACT FROM AUTHOR]

Objectives: The coseismic deformation field of 2017 Jiuzhaigou earthquake has been investigated by previous numerous studies. However, these studies most focus on the one-dimensional(1D) ground motion along the radar line of sight(LOS), thus resulting in anamorphic coseismic displacements. Methods: We construct high-quality three-dimensional(3D) coseismic deformation field using ascending and descending synthetic aperture radar(SAR) data from Sentinel-1A satellite with constraint of the elastic dislocation model to reflect the real movement patterns of 2017 Jiuzhaigou earthquake. Firstly,we use differential interferometry method to generate LOS coseismic deformation field with SAR images. Then, a two-step inversion algorithm is used to subdivide the fault plane, and obtain the geometric parameters and the optimal fault slip distribution. With constraint of this fault model, we take the variance component estimation approach to reconstruct 3D coseismic deformation field based on interferometric synthetic aperture radar(InSAR) measurements. Results: 3D coseismic deformation results show that the coseismic deformation field is dominated by horizontal displacement. In the north-south(N) direction, the maximum displacement of the hanging wall is －19.81 cm and 14.38 cm in the footwall. In the east-west(E) direction, the maximum displacement of the hanging wall is 18.37 cm for the northwestern, while that of the footwall is －7.84 cm for the Southeastern. In the vertical(U) direction, there is a little uplift in the northern of the fault and the maximum is about 3 cm. Conclusions: The derived north-south and east-west displacements are in good consistency of the global navigation satellite system investigations, indicating that combing InSAR measurements and elastic dislocation model to reconstruction 3D seismic deformation field is feasible and effective, which overcomes the problem of insufficient geodetic data and offers extensive future usage for measuring earthquake deformation. [ABSTRACT FROM AUTHOR]

The study of asperities is of great importance for seismic hazard analysis. This paper introduces the concepts of asperities, barriers and their source models, and reviews the progress of research on the determination of asperities by seismic geodesy, mainly discusses the technique and method for determining asperities from the aspects of medium structure analysis （high-intensity anomalies）, seismic activity analysis, the fault slip pattern, and the problems are analyzed. This paper also prospects the determination of the distribution of asperities on active faults, future researches will focus on joint inversion of geodetic data, joint geodetic and seismic geophysical data, and machine learning based methods to determinate the distribution of asperities. The study provides a strong theoretical basis for seismic safety evaluation. [ABSTRACT FROM AUTHOR]

Objectives: Manual seismic phase picking and earthquake catalog building become challenging because the number of seismic stations increases. With the rapid development of artificial intelligence, several deep learning models are developed for seismic phase picking, but their performance and applicability remain ambiguous. Methods: Phase-Net and EqT can extract relevant features at different levels from raw seismic waveforms and map them into probabilistic sequences. In this paper, the performance of these two widely-used deep learning models for earthquake detection and phase picking is investigated with the 2019 Ridgecrest earthquake (California, USA) sequence and the 2019 Weiyuan Ms 5.4 earthquake (Sichuan, China) sequence. Besides, the completeness and accuracy of the constructed earthquake catalogs are analyzed and evaluated by cross-validation. Results: The results show that the two models, though trained with datasets from different regions, perform well in cross-region applications and are comparable to manual analysis. EqT1 provides high detection precision with few false alarms, even under a low threshold. But EqT1 has a limited recall rate, implying that fewer earthquakes are detected compared with Phase-Net. The picking performance of Phase-Net is sensitive to the employed threshold. With the low and moderate thresholds, Phase-Net can detect more earthquakes than EqT1 and manual catalog, while registering a relatively low detection precision. With the high threshold, the precision of Phase-Net is comparable to that of EqT1. EqT2 is not recommended due to its inferior performance over EqT1 and Phase-Net. Conclusions: EqT1 provides a higher precision when being employed for seismic phase picking, leading to earthquake catalogs with better accuracy. Phase-Net has a higher recall rate and generates more complete catalogs. Both models can facilitate automatic and rapid construction of earthquake catalogs. [ABSTRACT FROM AUTHOR]

Objectives: The temporal‑spatial variation characteristic of the glacier surface velocity is an important indicator of dynamic change of glacier and can provide important information for glacier mass balance. Surface temperature, glacier bed slope and glacier altitude are all important factors that affect glacier surface velocity, and their respective effects need to be analyzed. Methods: In this paper, the offset ‑ tracking method was used to measure the surface velocity of the Gangnalou Glacier, based on high‑resolution Sentinel‑1A synthetic aperture radar (SAR) images ranging from January 2016 to December 2016. We divided the surface velocity into freezing period and ablation period based on whether surface temperature was greater than 0 °C or not. For further analysis, we extracted the central line glacier velocity, and then jointly used surface temperature and digital elevation model (DEM) to analyze the influences of temperature and glacier bed slope. Results: The results showed that surface velocity of freezing period was more stable and central line glacier velocity was faster than that of boundary which tended to 0 m/a. SAR measurements were affected by glacier ablation, accumulation and motion, and showed that the maximum surface velocity was 65.43 m/a during freezing period and 46.28 m/a during ablation period. This surface velocity field showed a partitioning phenomenon in which the velocities of the middle and lower parts of glacier tongue were significantly different from that of the upper part during ablation period. Conclusions: The surface velocity of the Gangnalou Glacier was affected by many complex factors, of which glacier ablation and glacier bed slope are main factors. The partitioning phenomenon in the ablation period could be better explained by increasing surface temperature and changing glacier altitude, which directly affected glacier ablation and accumulation. Additionally, by analyzing the effect of the glacier bed slope, we found that the Gangnalou Glacier followed the compressive and extending flow mode in the freezing period. [ABSTRACT FROM AUTHOR]

Objectives: Time-series analysis of interferometric synthetic aperture radar (InSAR) plays an important role in monitoring large-scale surface slow deformation. However, the impact of tropospheric delay limits the accuracy of mapping deformation. Tropospheric delay correction is crucial to InSAR deformation rate inversion objective. Methods: We focus on the northwestern margin of the Qinghai-Tibet Plateau and use three methods which are the empirical model linear correction, generic atmospheric correction online service for InSAR (GACOS) and ERA5 dataset released by the European Centre for Medium⁃Range Weather Forecasts (ECMWF) in the time-series InSAR inversion of deformation rate to study their applicability in this region. Results: By calculating the standard deviation in the non-deformation region with the mask technique, analyzing the correlation between deformation rate and topography, and comparing with the GPS data, the results show that three study areas from west to east, in the range of D136 (76.5°E— 79.7°E), D165 (80.5°E—83.7°E) and D19 (84.9°E—88.1°E), the standard deviations of linear corrected are decreased by 41.05%, 59.21% and 25.13%. The standard deviations of GACOS corrected are reduced by 38.76%, 55.97% and 30.73%, and those of ERA5 corrected are decreased by 10.05%, 30.11% and 20.15%, respectively. Besides, the correlation coefficients between deformation rate and elevation of the three profiles are 0.68, 0.93 and 0.60, respectively. With the increase of correlation coefficients, the advantage of linear correction becomes obvious. In addition, the comparison of LOS deformation rates between InSAR and GPS projected shows that the root mean square error of linear correction, GACOS correction and ERA5 correction in the three study areas are reduced by 46.07%, 51.28% and 35.51% respectively. Conclusions: The northwestern margin of the Qinghai-Tibet Plateau, all three methods can mitigate tropospheric effects, and the linear correction and GACOS correction perform better and have higher applicability. While the performance of ERA5 is slightly poor due to the density of ground monitoring stations. Considering that terrain, altitude, geographical location and other factors will affect the atmospheric delay, the atmospheric correction methods and correction effects applicable to different regions need to be comprehensively studied and analyzed based on the specific situation. [ABSTRACT FROM AUTHOR]

Objectives: At 15: 14 on October 17, 2016 (Beijing time), an earthquake with a magnitude of Mw 5.9 occurred in Zadoi County, Qinghai Province, which is located in the Qiangtang block in the middle of the Tibetan Plateau. The occurrence of the event provides an opportunity to deepen the understanding of the movement characteristic of regional fault zone. The fault slip model of the Zadoi earthquake is further investigated with geodetic observation to understand the fault rupture property of the event better. The rupture characteristic of typical faults around the epicenter is quantitatively studied using numerical method, which can make up for the inadequacies of qualitative interpretation of seismic fault rupture using feature of earthquake sequence and regional geological structure in the previous studies. Methods: To study this earthquake, coseismic deformation field was obtained using interferometric synthetic aperture radar (InSAR) technique and Sentinel-1 satellite ascending and descending synthetic aperture radar (SAR) data. On the basis of comparative analysis of existing studies related to rupture model of seismic fault, the fault slip model of this event was then inverted with the elastic half-space dislocation theory and non-negative least squares method. The average rakes of typical faults around the epicenter under regional strain field were calculated with boundary element method, and the earthquake fault slip was finally analyzed by combining the characteristic of regional faults, the fault slip model of the Zadoi earthquake and the result calculated by boundary element method. Results: The main results are given as follows: (1) The ascending and descending InSAR coseismic deformation field is continuous and smooth as a whole, and the local surface deformation feature around the epicenter is obvious. The standard deviations for the ascending and descending observations are 4.3 mm and 3.4 mm, respectively. The maximum subsidences along the line of sight of ascending and descending orbits are - 3.6 cm and - 3.8 cm, respectively. The deformation on both sides of the earthquake fault is asymmetrical. (2) The fault slip does not extend to the surface, which is mainly concentrated at - 3.80 km to - 16.17 km depth, and there is one significant slip area. The maximum value of fault slip is about 0.27 m, which is located at - 7.61 km to -8.56 km depth. The average slip angle is - 36.04°. The seismic moment is 7.70×1017 N·m, and the corresponding moment magnitude is Mw 5.9, which is generally consistent with the existing results derived from seismic wave and In SAR observations. (3) The fault slip model can explain the observed coseismic deformation field better. The root mean squares of the fitting residuals for the ascending and descending observations are 4.4 mm and 3.7 mm, which are close to the standard deviations of 4.3 mm and 3.4 mm for the corresponding observations. (4) The fault slip of the Zadoi Mw 5.9 earthquake may be related to the rupture of the NEE trending fault under regional strain field, which is dominated by left-lateral strike-slip with a normal component. Conclusions: The obtained ascending and descending InSAR deformation field can accurately reflect the coseismic deformation characteristics of the Zadoi Mw 5.9 earthquake. The derived fault slip model can finely reveal the coseismic slip distribution below the earth's surface. The analysis of the earthquake fault slip with boundary element method can make up for the inadequacies of qualitative interpretation in the previous studies. The related results can provide references for the study on the regional crustal movement and deformation, active fault and earthquake preparation. [ABSTRACT FROM AUTHOR]

Fukuda and Johnson (2010) proposed an inversion method associated with the Bayesian theory (hereinafter termed the F-J method) for linear-non-linear geophysical/geodetic problems. Since then this method has been widely applied to estimating globally optimal parameters and their precisions for linearnon- linear geophysical/geodetic models. Yet for the application of the F-J method the choice of Markov chain Monte Carlo (MCMC) sampling parameters somewhat affects the invered results. Additionally, searching the most appropriate sampling parameters is time-consuming. On the other hand, an iterative least squares method can also be applied to the inversion for linear-non-linear models if their non-linear parameters are linearized beforehand. However, this method depends on optimum initial values. To make full use of the advantages of the both methods, here we propose a hybrid method termed as the iterative least squares with initial values constrained by using the F-J method. The proposed method refers to the calculation of linear-nonlinear parameters using the F-J method just one time and to refining those parame⁃ ters using the iterative least squares method a few times. Thus, it reduces the computation time relevant to the F-J method on the one hand and gains a global solution after a few times of employing the iterative least squares method on the other hand. To verify the efficacy of the hybrid method, we make comparisons using synthetic and real data sets. We employ the F-J method, iterative least squares method with random initial values and iterative least squares method with initial values provided by the F-J method, respectively. Our results show that： (1) the choice of sampling parameters indeed affects the results by using the F-J method; (2) based on the iterative least squares method with random initial values, inverted results generally diverge and sometimes converge to wrong results for some synthetic tests, and (3) using the iterative least squares method with initial values provided by the F-J method produces converged results without the dependence on MCMC sampling parameters and initial values, as expected thanks to absorbing the merits of the global optimality of the F-J method and efficiency of the iterative least squares method. [ABSTRACT FROM AUTHOR]

With the improvement of space geodetic observation accuracy, the geodetic inversion model is more precise and detailed, and higher requirements are also put forward for the inversion algorithm. Focusing on the inversion of fault parameters in the spherical layered model, the defects of genetic algorithm is ana- lyzed and a new combinational inversion algorithm based on iterative least squares algorithm and genetic al- gorithm is proposed. The co-seismic deformation inversion mode due to seismic fault has set up considering the earth layering. The effectiveness of the combinational algorithm has been verified using the simulated data. In the inversion of genetic algorithm, it is often difficult to obtain good results of fault depth and slip distance.. The main reason is the strong correlation between these parameters and the secondary reason is the low sensitivity of depth and slip. The combinational algorithm proposed in this paper has achieved ideal results on faults of various dip angles and has practicality. [ABSTRACT FROM AUTHOR]

In order to study the activity characteristics of the Red River fault zone in recent years, the GPS measurements from 1999 to 2014 in the surrounding blocks of the Red River fault zone are modeled by block model, and the rigid block rotations, internal strain rates, fault slip rates and three-dimensional locking degree are obtained. The inversion results show that the block model considering the internal strain can significantly improve the fitting effect to the GPS velocities, the inverted slip rates of the Red River fault are in good agreement with the results of the velocity profiles. The locking degree of the Red River fault is roughly symmetrical that the middle section is relatively strong, and the southern and northern segments are weak. The locking degree of the southern, middle and northern sections are about 0.34-0.52, 0.67-0.75 and 0.26-0.53 respectively from the surface to 15 km depth, and the dextral slip rate deficit were 1.7, 3.0 and 1.4 mm /a, respectively. The distribution of strain field in the study area is calculated by the least squares collocation, it is found that the Red River fault zone is converted from compression in the south to tension in the north. The middle section is in the transfer zone of compression and tension, and its shear strain is lower than the northern and southern sections, which may be due to the stronger locking degree of the middle, so that the fault dislocation is smaller. [ABSTRACT FROM AUTHOR]

This paper focuses on block partitioning and strain calculation in the Sichuan-Yunnan region.First,the K-medoids clustering method is used to cluster the GPS horizontal velocity field in Sichuan-Yunnan.Next,the initial classification results are further clustered based on constraints from the geographical location and velocity field of GPS stations by using the improved K-medoids method.Subsequently,the F statistical test method is used to determine the boundary of each block.Finally,the strain parameters of each block are calculated using an integral rotation linear strain model and the relationship between horizontal motion,spatial distribution of strain field,and regional tectonic deformation is analyzed.The results of the velocity field clustering analysis of GPS stations in the Sichuan-Yunnan region are consistent with the results of the alternative block division methodology based on geological theory of plate division.The strain results,which are calculated using the integral rotation linear strain model,show that the Sichuan-Yunnan rhombic block has the maximum shear strain and the highestsurface strain rate gradient.In addition,this region has accumulated some elastic strain energy,an indicator of earthquake risk. [ABSTRACT FROM AUTHOR]

Earthquake geodesy is a new branch of modern geodesy, which was generated as a result of its thorough applications to various geoscience problems. Earthquake stress triggering based on geodetic data is one of the main research directions of earthquake geodesy, which is of great significance to earthquake prediction and disaster prevention and mitigation.This paper reviews and summarizes the researches on earthquake stress triggering from three aspects:static stress triggering, dynamic stress triggering and viscoelastic stress triggering, and introduces the latest progresses of relevant studies on earthquake stress triggering. The future development for the realm of earthquake stress triggering is also in prospect. [ABSTRACT FROM AUTHOR]

Trend removal is the most common approach in conventional least squares collocation (LSC) to deal with nonstationarity. Due to the inaccuracy of the trend model, conventional LSC can barely eliminate the drift component of the data that results in estimation bias of the local covariance function and error of the interpolation values. Here we present a refined LSC method to estimate the drift component of the field and compensate the residualfrom LSC. The refined method employs the mulitiquadric function to approach the drift and the collocation to estimate signals. We apply the refined method to a synthetic data set and coseismic displacement data from the 2009 L’Aquila, Italy earthquake, and compare the results of refined method with conventional methods. The statistical results of residuals indicate that the refined method can achieve a more accurate result than conventional methods and is affected less by the observation distribution. [ABSTRACT FROM AUTHOR]

Based on the distribution of aftershock sequences and the geology of Lushan, using the GPS and level measurement coseismal displacement data near the Lushan Earthquake, we constructed a curved fault model of the 2013 Ms 7.0 Lushan earthquake using the grid search and variance component estimation method. We executed a fault slip distribution inversion based on this curved fault model. The result shows that the fault is mainly a thrust fault with a sinistral trend. The earthquake occurred at 4.56~18.25 km in depth, the maximum slip was 0.70 m at the 12.64 km depth, and the corresponding seismic moment release was 8.77×1018N/m, equivalent to a Mw 6.57 earthquake. Based on a check board test of the curved fault model, we can distinguish an asperity shallower than 13 km in the fault depth, with a minimum area of 8 km×8 km. [ABSTRACT FROM AUTHOR]

Based on the function model of TS-InSAR (time series interferometric synthetic aperture radar) technique, this paper establishes stochastic function models (weighted/equal-weight) for single-master and multi-master image TS-InSAR method respectively to enrich the mathematical model of TS-InSAR. A simulation test is used to estimate the precision of model parameters for our equal-weighted function model (stochastic model). Compared to the equal-weight model, the precision of deformation parameters shows little improvement over the weighted model. However, complications in the weighted model means that much disk-space is consumed with low computational efficiency. Most computers therefore cannot undertake TS-InSAR analysis tasks with reasonable hardware configuration. At present, the equal-weight model is feasible for TS-InSAR. [ABSTRACT FROM AUTHOR]

The gravity field is a physical parameter reflecting the density change and dynamic characteristics of the earth under different circumstances including the solid earth tide, internal heat flow, mass exchange of solids and liquids, surface loads, and seismic tectonic movements. The time varied global gravity model has been provided by GRACE since 2002, but with the existing system error in GRACE and the need for focusing on local areas, post-processing is required when using GRACE products. In last decade, many algorithms have been shown to be effective. The ideas for these algorithms are reviewed in this article; a Gaussian filter with isotropic and non-isotropic types, the destriping filter, the empirical orthogonal functions method, wavelet analysis, and the Slepian function method. The future directions in post-processing algorithms are also discussed. [ABSTRACT FROM AUTHOR]

We propose a coseismic slip distribution inversion method based on variance component estimation (VCE), this method not only determines the weight of different data sets but also can get the smoothing factor value. To illustrate and validate this inversion method, we conducted inversions on synthetic data sets. Based on the Bayesian framework and according to the posterior probability density distribution of the unknown parameters, the proposed solution is comparted to one of the linear-non-linear inversion solutions to further demonstrate the use of the proposed method. We conduct inversions on the 2003 Bam earthquake with the proposed method and linear-non-linear inversion method, the spatial cross correlation of the resulting slip distribution was about 0.999, the depth of the max slip of the both were 3.04 m and the depth had little difference, the former was 4.50 km, the latter was 4.47 km. The mean slip in the former was 0.714 m, the latter was 0.718 m. But the inversion time of the former was 227 s, and only about 1/8 000 of the later (reaching 1.5×106 s, about 17 d).These results show that the VCE method is effective and faster than the linear-non-linear inversion method. [ABSTRACT FROM AUTHOR]