The migration of the crustal deformation peak area in the eastern Himalayan Syntaxis inferred from present-day crustal deformation and morpho-tectonic markers

The present-day Global Positioning System(GPS)velocity field shows that the Indian Plate is not a complete rigid block,as its northeastern corner has been torn off and clockwise rotating relative to the main part.With the updated GPS velocity data,the Euler vector of the northeastern corner of the Indian Plate relative to the stable main plate is deduced as(89.566±0.06°E,26.131±0.05°N,1.34±0.11°/Myr).The peak area of the present-day crustal deformation is located in the Chayu deformation belt with the compressional dilation strain rate over 160 nanostrain/yr.However,the Namche-Barwa Syntaxis with the massive crustal thickening and intense surface erosion is generally considered to be the previous locus of the strongest compressional stress in the Eastern Himalayan Syntaxis over long geological timescales.Thus,there is a discrepancy between the previous and present-day crustal deformation peak areas.We argue the migration of the crustal deformation peak area with a total distance of about 120 km and ascribe it to the variation of stress conditions caused by northeast India’s clockwise rotation.

Automatic Monitoring System for 3-D Deformation of Crustal Fault Based on Laser and Machine Vision

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.

Upper crustal deformation characteristics in the northeastern Tibetan Plateau and its adjacent areas revealed by GNSS and anisotropy data

The northeastern part of the Tibetan Plateau is a region where different tectonic blocks collide and intersect,and large earthquakes are frequent.Global Navigation Satellite System(GNSS)observations show that tectonic deformation in this region is strong and manifests as non-uniform deformation associated with tectonic features.S-wave splitting studies of near-field seismic data show that seismic anisotropy parameters can also reveal the upper crustal medium deformation beneath the reporting station.In this paper,we summarize the surface deformation from GNSS observations and crustal deformation from seismic anisotropy data in the northeastern Tibetan Plateau.By comparing the principal compressive strain direction with the fast S-wave polarization direction of near-field S-wave splitting,we analyzed deformation and its differences in surface and upper crustal media in the northeastern Tibetan Plateau and adjacent areas.The principal compressive strain direction derived from GNSS is generally consistent with the polarization direction of fast S-waves,but there are also local tectonic regions with large differences between them,which reflect the different deformation mechanisms of regional upper crustal media.The combination of GNSS and seismic anisotropy data can reveal the depth variation characteristics of crustal deformation and deepen understanding of three-dimensional crustal deformation and the deep dynamical mechanisms underlying it.it.

Geodetic constraints on contemporary three-dimensional crustal deformation in the Laji Shan—Jishi Shan tectonic belt

The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.

Crustal Deformation Derived from GPS in the Chinese Mainland from 1991-2004

Based on GPS data from 1991- 2004 and the least-squares collocation method,we analyze the crustal deformation in the Chinese mainland. The results show that the first-order crustal deformation is unchanged in different periods in the Chinese mainland,which reflects the background of regional tectonic activity. The strain rate is much higher in Western China,especially in the Qinghai-Tibetan Plateau and Sichuan-Yunnan area. The variations in different periods are related with seismicity of strong earthquakes during the same time. The GPS data after 2004 shows the post-seismic deformation of the 2001 Kunlun Mountains M S8. 1 earthquake.

Horizontal crustal deformation in Chinese Mainland analyzed by CMONOC GPS data from 2009-2013

In this study, we analyze the regional GPS data of Crustal Movement Observation Network of China （CMONOC） observed from 2009-2013 using the BERNESE GPS software, and then the preliminary results of horizontal velocity field and strain rate field are presented, which could reflect the overall deformation features in the Chinese mainland from 2009-2013. Besides, the velocity error and the probable factors that could influence the estimate of long-term deformation are also discussed.

Crustal Deformation Revealed by GPS in Kumaun Himalaya,India

The foremost Global Positioning System(GPS) derived measurements in the Kumaun Himalaya indicate that most of the crustal motion of the Indian plate is accommodating towards the base as well as on the hanging wall of Main Central Thrust(MCT).Deformation pattern within the Kumaun Himalaya varies from south to north and indicates maximum deformation rate near MCT.Our study,based on the campaign mode GPS survey during 2003- 2006,reveals that the area between north of North Almora Thrust(NAT) and at the base of Great Himalaya registers maximum strain rate,which is lowered towards the Trans Himadri Fault(THF).The GAMIT-GLOBK processed campaign data of the area show that currently,the Himalayan Frontal Fault(HFF) and Main Boundary Thrust(MBT) are locked with the Indian plate,and a 6.7 ± 2.5 mm/yr of horizontal shortening is taking place between the Lesser Himalaya and Peninsular India.

Monitoring Crustal Deformation by GPS and InSAR in the Three Gorge Area

The on-going Three Gorges Project (TGP) aims to build one of the largest hydropower stations in the world. Previous investigations have concluded that the reservoir is likely to induce medium-to-intense earthquakes. 23 GPS stations have been established to maintain a geodetic and seismological monitoring network around the reservoir to monitor seismicity and crustal deformation, and to facilitate mitigation activities in case an intense earthquake occurs. The velocity of GPS site was derived from 3 repeated GPS surveys. Meanwhile, another effort has been made to investigate the feasibility of application of satellite interferometric synthetic aperture radar (InSAR) techniques in detecting crustal deformation possibly caused by impoundment of the Three Gorges Reservoir. It has been made to derive digital elevation models (DEM) using European Remote Sensing (ERS) synthetic aperture radar (SAR) imagery. Pairs of ERS SAR images in raw format are processed to generate digital elevation models. This effort will help us evaluate the accuracy of the InSAR techniques for further derivation of background deformation patterns and future detection of reservoir-induced crustal deformation in the area.

On the physical model of earthquake precursor fields and the mechanism of precursors＇timespace distribution（Ⅲ）──anomalies of seismicity and crustal deformation and their mechanisms when a strong earthquake is in prep

By studying the seismicity pattern before 37 earthquakes with M≥6. 0 in North China and the pattern of crustal deformation in the Capital Area from 1954 to 1992, some abnormal characteristics of these patterns before strong earthquakes have been extracted. A comparison has been made between the anomalies of these two kinds of Patterns. From the results we can know the following. ① Before a strong earthquake, the seismicity will strengthen and the crustal deformation rate will increase. ② Several years before a strong earthquake, there will be seismic gaps and deformation gaps around the epicenter of the quake. ③ The dynamic parameters of patterns all show a decrease in information dimension. This means that the crustal deformation has become more and more localized with time and it gives an important indication showing that a strong earthquake is in preparation. At the end of the paper, the physical mechanisms of the abnormal patterns of seismicity and crustal deformationhave been explained in a unified way in terms of the earthquake-generating model of a inhomogeneous strongbody in inhmogeneous media.

Study on scale dependence of strain value obtained from crustal deformation data

Using statistic analysis, the scale dependence of crustal stain value from crustal deformation data is studied. We found that there exists obvious correlation between strain value and computational figure scale. Along with increasing of figure element scale, the statistic mean value and mean square deviation of strain present power law attenuation. Based on this analysis, the necessity of strain value scale normalization is suggested for calculating strain field using crustal deformation data and the normalization method is proposed in this paper.

Research on present crustal deformation in the southern Tianshan (Jiashi) region by GPS geodesy

The pattern and range of present crustal movement as well as characteristic of deformation-strain play a key role in cognizing seismogenic mechanism in the Jiashi region, Xinjiang, northwestern China. Using GPS geodesy in 1994 and 1998, here we give geodetic evidence of rapid convergence of about 19 mm/a across the westem Tianshan, which is about 50% greater than the seismic moment solution (13 m/a) by assembling major enrthquake in the 20th century. The discrepancy of deformation rate between geodetic observation and seismic energy releasing indicates the possibilities that, there exists a lot of aseismic strain and strain during seismic interval in the westem Tianshan, or seismic fault slip in this century could not be enough to compensate the present deformation in the whole area. Whichever it maybe, from the view of accumulation of stress-strain, it suggests that there will be potential strong eathquakes in the western segment of Tianshan and the northeastern corner of Pamir in a long period.

Advantages of GNSS in Monitoring Crustal Deformation for Detection of Precursors to Strong Earthquakes

Earthquake predictions inChinahave had rare successes but suffered more tragic setbacks since the Xintai earthquake in 1966. They have developed with twists and turns under the influence of the viewpoint that earthquakes are unpredictable etc. Though the Wenchuan earthquake of M8.0 in2008 inChina and the 2011 Tohoku earthquake of M9.0 inJapan were failed to predict, the GPS observations before and after these 2 events have shown that there were precursors to these events and large earthquakes are predictable. Features of different observation techniques, data processing methods are compared and some recent studies on precursory crustal deformations are summarized, so various advantages of GPS technique in monitoring crustal deformation are emphasized. The facts show that anomalies or precursors detected from GPS observations before the great Wenchuan earthquake have been the most remarkable results of explorations on crustal movements and earthquake precursors in China. GPS is in deed an excellent observation technique for earthquake prediction.

Vertical crustal deformation velocity and its influencing factors over the Qinghai-Tibet Plateau based on satellite gravity data

The uplift of the Qinghai-Tibet Plateau(TP)strongly influences climate change,both regionally and globally.Surface observation data from this region have limited coverage and are difficult to obtain.Consequently,the vertical crustal deformation velocity(VCDV)distribution of the TP is poorly constrained.In this study,the VCDV from the TP was inverted by using data from the gravity recovery and climate experiment(GRACE).We were able to obtain the vertical crustal movement by deducting the hydrological factors,based on the assumption that the gravity signal detected by GRACE is mainly composed of hydrological factors and vertical crustal movement.From the vertical crustal movement,we inverted the distribution of the VCDV across the TP.The results showed that the VCDV of the southern,eastern,and northern TP is~1.1 mm/a,~0.5 mm/a,and−0.1 mm/a,respectively,whereas that of the region between the Qilian Haiyuan Fault and the Kunlun Fault is~0.0 mm/a.These results are consistent with the distribution of crustal deformation,thrust earthquakes and faults,and regional lithospheric activity.The hydrology,crustal thickness,and topographic factors did not change the overall distribution of the VCDV across the TP.The influence of hydrological factors is marked,with the maximum differences being approximately−0.4 mm/a in the northwest and 1.0 mm/a in the central area.The results of this study are significant for understanding the kinematics of the TP.

Current crustal motion and deformation inthe Chinese mainland and its surroundingarea determined from GPS data

Based on the geodetic data taken from the National GPS Network established by China Climbing Program 'Investigation of Crust Motion and Geodynamics in Modern Time', we derived the movement velocities of the GPS sites.In terms of the power series expansion of a rotation function for horizontal velocities on a spherical surface proposed by Hames and Holt (1993), we computed the horizontal velocity and strain-rate field.We preliminarilystudied the appearances and characteristics of the present-day crustal movement and deformation in the Chinesemainland with the computed results. The researches demonstrated (1)The present-day crustal movement anddeformation in the Chinese mainland are being jointly controlled by indian, Pacific and Philippines Ocean Platesand Siberia-Mongolia block, and these three large plates and block form a situation of triparite confrontation, butIndian Plate seems to play a leading role;(2) The North-South Earthquake Zone plays an important adjustment rolein the present-day crustal movement and deformation process. displaying clear characteristics of demarcation lineof tectonics in large areas, (3)There seems to be another adjustment zone along the latitude line approximate N35,but its characteristics are less obvious than that of the former; (4) Dynamic actions of these three large plates andblock on the Chinese mainland are dynamic stable; appearing in stable push-press velocities. These results aregenerally accorded with the results determined from geology, geophysics, and seismology. By the contrast withseismicities. if appears preliminarily that there is some corresponding relation between intense shear st fain zoneand future strong seismicity area. but this problem needs further examination of earthquake examples.

The effect of large reservoirs impoundment to the spatial and temporal variations of regional crustal deformation in Hubei Province, China

The total capacity of Three Gorges Reservoir（TGR） and Danjiangkou Reservoir（DJR） is large and has significant seasonal fluctuations, which give rise to crustal instability. In this research, we focus on studying the temporal and spatial variation of crustal deformation in Hubei Province caused by reservoir impoundment of TGR and DJR.The Digital Elevation Model, historical hydrological information, GPS monitoring data and load-induced deformation model are combined to monitor the crustal deformation. The modeled results indicate that in the trapezoidal area between the TGR and DJR, the average vertical deformations at different latitudes have different variation tendencies. The vertical deformation modulus and fluctuation amplitude are larger at the latitude of 33 N/32.5 N from 2003 to 2006 and at the latitude of 31 N/32.5 N from 2008 to 2014, while the latter are much larger than the former. Moreover, from2008 to 2014, the frequency and the intensity of seismic activities are all enhanced significantly in this region. The modeled results at the GPS sites are consistent with the vertical displacement of GPS monitoring results in trends and the waveform. It can be inferred that the seasonal deformation is elastic. The horizontal deformation components have the same variation trends with that at each GPS monitoring station,which demonstrates that the whole region is moving toward the southeast. The spatial variation of crustal deformation demonstrates that the impoundment of TGR in2003 causes significant vertical displacements, with the maximum modulus of 32 mm downward located in Xiangjiang River＇s estuary. When the water storage increases, the maximum value will become larger, and the location will move toward the upstream.Besides, the earthquakes occurred more frequently in the region with maximum deformation modulus.

Gravity changes and crustal deformations before the Menyuan,Qinghai Ms6.4 earthquake of 2016

In this study, the relative gravity data(2012 e2015), GPS data-derived horizontal deformation(2011 e2014) and the background vertical deformation from the leveling measurements(1970 e2011) in the northeastern margin of Tibetan Plateau were processed to systematically analysis the mechanism of temporalespatial patterns and the relationship with Menyuan Ms6.4 earthquake. It can be summarized in the following: 1) The regional gravity changes, the GPS and the vertical deformational showed an intense spatial relationship: the gravity increased along with the direction of horizontal movement, and decreased with the crustal uplift and vice versa, which reflected the inherited characteristics of geotectonic activities. 2) The crustal deformations were closely related to the active faults. The contour lines of gravity changes and vertical deformation were generally along with the Qilian-Haiyuan fault(strike is NWW), and the crustal horizontal deformation showed left-lateral strike slip motion near the Qilian-Haiyuan fault. 3) Menyuan Ms6.4 earthquake occurred in the high negative gravity variation area and a high gradient formed in regions, positive and negative variation of gravity amount to 110 m Gal.Specifically, a borderline of positive and negative gravity located in the south of epicenter along the north edge of Qilianshan fault and Lenglongling fault, as well as the vertical and/or horizontal deformation is intensely. The extrusion deformation, surface compression rate and gravity changes were obvious near the epicenter of 2016 Menyuan Earthquake.

Field of vertical crustal deformation in North China and the feature of its dynamic evolution

Based on the data of precise leveling surveys for 30-odd years and using unified adjustment method unified starting point of calculation and unified network,contour maps of the vertical crustal deformation rate in North China during the periods of 1965-1975,1975-1979,1979-1983 and 1983 1988 have been drawn.Meanwhile,the evolution of vertical crustal deformations has also been studied from a dynamic viewpoint. The results of analysis show that there is an obvious correspondence between the regular variations of the vertical crustal deformation field and the seismic cycles.Furthermore,the paper has also inferred that this correspondence might be related to the micro-variations of the regional stress/strain field. Finally,some problems related to the vertical deformation field and earthquake prediction have been discussed.

Analysis of GAMIT/GLOBK in high-precision GNSS data processing for crustal deformation

The advances in satellite navigation and positioning technology and the worldwide establishment of continuoustracking stations have greatly promoted the development and application of the high-precision Global Navigation Satellite System(GNSS).GAMIT/GLOBK,as a popular high-precision GNSS data-processing software,has been widely used in monitoring crustal deformation,tsunami,iceberg,etc.Based on the basic observations and various geophysical models processed by GAMIT/GLOBK,we analyze the influence of the correction of applied geophysical models,and describe the techniques of parameter estimation and accuracy assessment.In addition,taking the present crustal movement in the Chinese mainland and the MW7.8 earthquake in Nepal as examples,we discuss the applications of GAMIT/GLOBK in crustal deformation monitoring and its future prospect.

Monitoring Crustal Deformations with Radar Interferometry: A Review

The crustal movements, probably motivating earthquakes, are considered as one of the main geodynamic sources. The quantitative measurements of ground surface deformations are vital for studying mechanisms of the buried faults or even estimating earthquake potential. A new space-geodetic technology, synthetic aperture radar interferometry (InSAR), can be applied to detect such large-area deformations, and has demonstrated some prominent advantages. This paper reviews the capacity and limitations of InSAR, and summarises the existing applications including some of our results in studying the earthquake-related crustal motions. Finally it gives the outlook for the future development of InSAR.

Essential Features of Tectonic Movement Revealed by Crustal Vertical Deformations in the Mainland of China

Based on the precise reieveling data of more than 260,000 km carried out from 1950 to 1991 in the Chinese mainland,recent crustal vertical movement is studied.By means of some quantitative indices,such as the pattern of crustal vertical movement,the intensity of differential movement,the maximum gradient and its distribution,etc.,the properties of movements are analyzed on a large scale.The results suggest that all the properties have a profound tectonic background of their own and are closely related to the zoning and seismic activity of active subplates.The driving force for the movement comes mainly from the northward push of the India plate acting on the Eurasia plate.The effects of motions of the Pacific and Philippine Sea plates in the east are much less significant.