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Characteristics of present-day active strain field of Chinese mainland

Earthquake Science 2008年第6期21卷 562-572页

作者：郭良迁李延兴杨国华胡新康 First Crust Monitoring and Application Center China Earthquake Administration

On the basis of the GPS data obtained from repeated measurements carried out in 2004 and 2007,the horizontal principal strain of the Chinese mainland is calculated,which shows that the direction of principal compressive strain axis of each subplate is basically consistent with the P-axis of focal mechanism solution and the principal compressive stress axis acquired by geological *** indicates that the crustal tectonic stress field is relatively stable in regions in a long *** principal compressive stress axes of Qinghai-Tibet and Xinjiang subplates in the western part of Chinese mainland direct to NS and NNE-SSW,which are controlled by the force from the col-lision of the Eurasia Plate and India *** principal compressive strain axes of Heilongjiang and North China subplates in the eastern part direct to ENE-WSW,which shows that they are subject to the force from the collision and underthrust of the Eurasia Plate to the North America and Pacific *** the same time,they are also af-fected by the lateral force from Qinghai-Tibet and Xinjiang *** principal compressive strain axis of South China plate is WNW-ESE,which reflects that it is affected by the force from the collision of Philippine Sea Plate and Eurasia Plate and it is also subject to the lateral force from Qinghai-Tibet *** is apparent from the comparison between the principal compressive strain axes in the periods of 2004～2007 and 2001～2004 that the acting directions of principal compressive stress of subplates in both periods are basically ***,there is certain difference between their directional concentrations of principal compressive stress *** sur-face strain rates of different tectonic units in both periods indicate that the events predominating by compressive variation decrease,while the events predominating by tensile change increase.

关键词： GPS strain field compressive strain axis stress tectonic motion

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Processes of the displacement field change of the 2009 April 6 M_W6.3 L'Aquila earthquake using persistent scatterer and small baseline methods

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Earthquake Science 2013年第5期26卷 293-299页

作者： Sanming Luo Liming Fu Shuang Zhu Qinglong He Wenni Wan Bo Yang First Crust Monitoring and Application Center China Earthquake Administration

Using a time series method that combines both the persistent scatterer and small baseline approaches, we analyzed 9 scenes Envisat ASAR data over the L＇Aquila earthquake, and obtained a Shocke＇s displacement field and its evolution processes. The results show that：（1） Envisat ASAR clearly detected the whole processes of displacement field of the L＇Aquila earthquake, and distinct variations at different stages of the displacement field. （2） Preseismic creep displacement → displacement mutation when faulting → constantly slowed down after the earthquake. （3） The area of the strongest deformation and ground rupture was a low-lying oval depression region to the southeast. Surface faulting within a zone of about 22 km× 14 km, with an orientation of 135°, occurred along the NW-striking and SW-dipping Paganica-S. Demetrio normal fault. （4） In analyzing an area of about 54 km x 59 km, bounded by north-south axis to the epicenter, the displacement field has significant characteristics of a watershed： westward of the epicenter shows uplift with maximum of 130 mm in line-of-sight （LOS）, and east of the epicenter was a region with 220 mm of maximum subsidence in the LOS, concentrating on the rupture zone, the majority of which formed in the course of faulting and subsequence.

关键词： PS method SB method Incorporatingprocessing Time series L'Aquila earthquake Displacement field

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crust deformation & the model deduction of generation mechanism of Wenchuan earthquake

Crust deformation & the model deduction of generation mechan...

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11th International Conference on Analysis of Discontinuous Deformation, ICADD 2013

作者： Bo, W.J. Yang, G.H. Zhang, F.S. First Crust Monitoring and Application Center CEA Tianjin China

The ground rising of the area to the south of the epicenter of Wenchuan China MS8.0 earthquake obtained from yearsâTM mobile leveling, the variation curve of short leveling across the fault on the epicenter, pre-earthquake horizontal deformation by GPS observation during two periods in the Sichuan-Yunnan area, and the vertical and horizontal co-seismic crust movement monitored by GPS in the area around the epicenter are shown in this paper. A model for the generation of intra-plate thrust strong earthquake, shortly called PUTDOWN (Press-Up then Thrust-Down) model, is given by integrated analysis and deduction. And then all the anomalies shown in the Figures from different measurement can be understood well coincidently. The result in the paper shown that crust deformation can be monitored precisely with leveling and GPS survey. With the accumulation of monitoring data and earthquake samples, some regulations of crust deformation before earthquake occurrence may be found. © 2013 Taylor & Francis Group.

关键词： Earthquakes

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Analysis on the noises from continuously monitoring GPS sites

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Acta Seismologica Sinica(English Edition) 2007年第2期20卷 206-211页

作者：黄立人符养 First Crust Monitoring and Application Center China Earthquake Administration Beijing Institute of Applied Meteorology

In this paper, we analyze the time series of site coordinates of 27 continuously monitoring GPS sites covered by the crustal Movement Observation Network of China over the whole country. The data are obtained in the period from the beginning of the observation to the November of 2005. On the basis of data processing, we analyze the power spectrum density of coordinate component noise at each site and calculate the spectral indexes manifesting the noise property of each component. The spectral indexes indicate that for most sites, the noise of time series of each coordinate component can be addressed by the model of white noise ＋ flicker noise; and for a small amount of sites, it can be described by the model of white noise ＋ flicker noise ＋ random walk noise. We also quantitatively estimate each noise component in the model by using the criterion of maximum likelihood estimation. The result shows that the white noise in the time series of GPS site coordinates does not constitute the main part of noise. Therefore, the error estimation of site movement parameters is usually too small, or too optimistic if we consider the white noise only. Correspondingly, if this factor is not fully considered in explaining these movement parameters, it might mislead the readers.

关键词： continuously monitoring GPS sites time series spectral index noise component maximumlikelihood estimation

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Coseismic displacements of the 2011 Tohoku-Oki Earthquake measured by high-rate GPS

Coseismic displacements of the 2011 Tohoku-Oki Earthquake me...

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11th International Conference on Analysis of Discontinuous Deformation, ICADD 2013

作者： Zhan, W. Huang, L.R. Yang, B. Feng, S.T. Liu, Z.G. Meng, X.G. First Crust Monitoring and Application Center CEA Tianjin China

In order to research characteristics of the coseismic displacements produced by the 2011 Tohoku-Oki Earthquake, we used the precise point positioning technology to process the high-rate GPS observations of five stations spanning the event, and presented the kinematic distribution of displacements. The results illustrate that the displacement amplitude of GPS stations decreases with increasing epicentral distance and the displacement amplitudes of near-field stations in horizontal directions are larger than that in vertical direction. Taking MIZU as an example, the estimated maximum displacement is 2.87 m in the east-west direction, 1.84 m in the north-south direction and 0.30 m in the vertical direction. Furthermore, the characteristics of the postseismic rebound in horizontal direction are obvious. Then we implement the S-transform to analyze the energy change associated with the frequency of coseismic horizontal displacements at the station MIZU. The results illustrate that the energy is concentrated in the frequency range of 0â0.1 Hz and the energy associated with the frequency range of 0â0.045 Hz significantly increases when the seismic wave arrives. © 2013 Taylor & Francis Group.

关键词： Global positioning system

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QUAD METHOD FOR IDENTIFYING RELATIVELY STABLE STATIONS

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大地测量与地球动力学 2003年第B12期23卷 23-29页

作者： Huang Liren (first crust monitoring and application center, CEA, Tianjin 300180,China) First Crust Monitoring and Application Center CEA Tianjin 300180China

The QUAD(Quasi-Accurate Detection of gross errors) method which is originally developed to detect gross errors in the geodetic data is extended and used to select and identify relatively stable stations. The formulas and algorithm are described in detail. Some problems that should be noticed in the use of this method are discussed. Finally, this method is applied to some data observed in North China as an example.

关键词： GPS测量稳定测点 QUAD方法误差的亚精确测定 QUAD方法的特殊问题

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AN ACCURATE MODEL FOR CALCULATING CORRECTION OF PATH FLEXURE OF SATELLITE SIGNALS

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大地测量与地球动力学 2003年第B12期23卷 14-18,29页

作者： Li Yanxing ,Hu Xinkang,Shuai Ping and Zhang Zhongfu (first crust monitoring and application center, CEA, Tianjin 300180, China) First Crust Monitoring and Application Center CEA Tianjin 300180 China

The propagation path of satellite signals in the atmosphere is a curve thus it is very difficult to calculate its flexure correction accurately, a strict calculating expressions has so far not been derived. In this study, the flexure correction of the refraction curve is divided into two parts and their strict calculating expressions are derived. By use of the standard atmospheric model, the accurate flexure correction of the refraction curve is calculated for different zenith distance Z . On this basis, a calculation model is structured. This model is very simple in structure, convenient in use and high in accuracy. When Z is smaller than 85°,the accuracy of the correction exceeds 0.06 mm. The flexure correction is basically proportional to tan 2 Z and increases rapidly with the increase of Z . When Z >50°,the correction is smaller than 0.5 mm and can be neglected. When Z >50°, the correction must be made. When Z is 85° , 88° and 89° , the corrections are 198 mm, 8.911 m and 28.497 km, respectively. The calculation results shows that the correction estimate by Hopfield is correct when Z ≤80 °, but too small when Z =89°. The expression in this paper is applicable to any satellite.

关键词：精确模型卫星信号弯曲路径校正计算卫星信号传播的几何关系计算公式

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Analysis of Dynamic Variations of crustal Density in the Longmenshan Area before the Wenchuan M_S8.0 Earthquake

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Earthquake Research in China 2015年第3期29卷 303-318页

作者： Li Yuan Niu Anfu Liu Xikang Zhao Jing First Crust Monitoring and Application Center CEA China Earthquake Networks Center

Based on the repeated gravity observation data from 1996 to 2007 from the Longmenshan gravity network, which has been dealt with by adjustment processing, the benchmark interference removal and impact of elevation changes removal, and by using the 3-D inversion method to reflect underground density, we analyze the characteristics of Longmenshan regional dynamic crustal density at depths of 25km, 20km and 15kin. The results show that in the Wenchuan earthquake preparation process, the regional density field showed marked characteristics both in time and space distribution. From the point of time process, the density change trend in the ten years before the earthquake presents a periodic change pattern： steady phase, dramatic stage, slow reducing phase and slow increase phase. The degree of density changes is from large to small, which means that earthquake gestation has reached the final stage. From the point of space distribution, density change distribution has a tendency of ＂dispersion--relative concentration＂, this shows that before the earthquake, the entropy of the underground density field was decreased. In addition, dramatic density changes often occur in the Longmenshan fault zone and western Sichuan plateau. Also, with the increase of depth, the trend of density change is more and more obvious. Through comparative analysis, the influence of density change on gravity is much bigger than that from height change.

关键词： 3-D inversion Dynamic change of density Wenchuan earthquakeLongmenshan fault zone The influence factors of gravity

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Simulation of land subsidence in North China based on campaign GPS data in a decade

Simulation of land subsidence in North China based on campai...

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11th International Conference on Analysis of Discontinuous Deformation, ICADD 2013

作者： Yang, G.H. Liu, Z.G. Feng, S.T. Liang, H.B. First Crust Monitoring and Application Center China Earthquake Administration Tianjin China

Campaign GPS observation is one of the primary methods to determine horizontal crustal deformation, whereas the vertical component of the observation is not adequately utilized due to its relatively larger error. However, the significant land subsidence in some places in the North China Plain where many GPS stations are situated makes it feasible to analyze the vertical component of the GPS data. In this paper, we have obtained accurate results from 4 sets of observations for the GPS stations in North China from 1999 to 2007 and present an analytic filtering method using multikernel functions to simulate the land subsidence. The results are as follows. (1) Vertical deformation field can be obtained more efficiently if a better data processing method is used and the time interval between campaign observations is longer. (2) In the North China Plain, the area of land subsidence is estimated to be up to 90,000 square kilometers with the maximum subsidence rate of 55 mm/a in one of the subsidence funnels because of the excessive exploitation of groundwater. © 2013 Taylor & Francis Group.

关键词： Subsidence

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Deformation-strain field in Sichuan and its surrounding areas based on GPS data

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Geodesy and Geodynamics 2015年第3期6卷 203-209页

作者： Chen Fuchao Ta La Chen Juzhong School of Geodesy and Geomatics Wuhan University First Crust Monitoring and Application Center China Earthquake Administration

The strain rate in Sichuan and its surrounding areas, and the activity rate and strain rate in two block boundary fault zones were calculated according to the block movement parameters estimated using the station speed obtained from regional GPS station observation data in these areas for 2009e2011 and GPS continuous station data for 2011e2013. The movement field characteristics in these areas were analyzed with the Sichuan Basin as the reference. Results show that the principal strain rate and maximum shear strain rate of the Bayan Har block were the largest, followed by those of the Sichuane Yunnan block and Sichuan Basin. The deep normal strain rate in the Longmenshan fault zone was compressive and large over the study period. The normal strain rate in the Xianshuihe fault zone was tensile.

关键词： Sichuan and its surrounding areas Displacement vec

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