The Application of GNSS to Fault Deformation Studies

Great earthquakes often occur along or near active fault belts. Thus,monitoring and research on fault deformation are quite important. Methods such as short-leveling,shortbaseline and integrated monitoring profile across fault belts have been used to monitor fault activities for many years. GNSS observations are mainly used to obtain the horizontal velocity field in large areas and to study the activities and deformation of major blocks.GNSS technology has been used to monitor and study the deformation of faults from a different aspects. In this paper,some applications and new explorations of GNSS are discussed. They are:( 1) Research and monitoring of strike-slip activities of faults with GNSS.( 2) Research and monitoring of vertical activities of faults with GNSS.( 3)Investigating the laws of deformation of blocks on the sides of fault zone and setting up strain models to deduce the activities and deformation of faults with respective models and compare the deduced results with the actual measurements across fault. It is concluded that a larger discrepancy between the deduced and the observed deformation indicates a stronger interaction between the blocks,which can be important for predicting the location of a strong earthquake and assessing seismic hazard,as well as the seismicity trend.

Deformation of the Haiyuan-Liupanshan fault zone inferred from the denser GPS observations

The Haiyuan-Liupanshan fault, an active tec- tonic feature at the Tibetan Plateau＇s northeastern bound- ary, was ruptured by two M8 earthquakes （1920 and 1927） bracketing an unbroken section （the Tianzhu seismic gap）. A high seismic hazard is expected along the gap. To monitor deformation characteristics and do a seismic risk assessment, we made measurements at two newly built campaign-mode Global Positioning System （GPS） stations and 13 pre-existing stations in 2013 and 2014. Adding existing data from 1999 to 2014, we derived a new velocity field. Based on the horizontal velocity, we used three block models to invert the deformation of four crustal blocks. The results suggest non-uniform deformation in the interior of the Lanzhou block, the Ordos block and the Alaxan block, but uniform deformation in the Qilian block. Fault slip rates derived from block models show a decreasing trend from west to east, （2.0-3.2 mm/a on the Haiyuan fault to 0.9-1.5 mm/a on the Liupanshan fault）. The Haiyuan fault evidences sinistral striking-slip movement, while the Liupanshan fault is primarily thrusting due to transformation of the displacement between the strike-slip and crustal shortening. The locking depth of each seg- ment along the Haiyuan fault obtained by fitting the fault parallel velocities varies drastically from west to east （21.8-7.1 km）. The moment accumulation rate, calculated using the slip rate and locking depth, is positively corre- lated with the locking depth. Given the paucity of large seismic events during the previous millennium, the Tuo- laishan segment and the Maomaoshan segment have higher likelihood of nucleation for a future event.

Dynamic Analysis of Deformational Structures of the Xianniishan Fault Zone in the Three Gorges of the Yangtze River

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannushan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of σI is N-S in direction with differential stresses of 150-250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.

Relation of deformation behavior with precipitation and groundwater of the Babaoshan fault in Beijing

We discuss the influence of precipitation and groundwater on the deformation behavior of the Babaoshan fault of Beijing by using long-term observation data from Dahuichang station during 1970-2003. The results show that a) the pore pressure on fault zone as well as the fault deformation behavior exhibited periodically variation as precipitation changed steadily and periodically; b) the periodicity of the pore pressure of fault zones disappeared and the manner of fault deformation behavior changed when precipitation was small and/or was in aberrance. This implies that rainfall plays a key role in fault deformation behavior through changing the pore pressure of fault zones. Combining the existing results about the Babaoshan fault, it is concluded that precipitation and groundwater may adjust the stress/strain field by controlling the deformation behavior of the fault, which can provide direct observation evidence for the interaction of fluid and solid in shallow crust of the Earth.

Unstable fault deformation and information synthesis

Based on the analyses of 75 pieces of fault deformation monitoring data obtained in the Region of Capital Circle(RCC) in many years, two major expressions of fault deformation anomaly in the unstable period of crustal deformation are proposed in the paper, one is the medium term variation lasting 1～2 year or longer time, the other is the rapid deformation of 1～3 months. When the above mentioned two kinds of variations appear in groups, it may be associated with strong seismic activities in North China. In this paper, the method of information synthesis has been used to obtain the common characteristics from individial fault deformation and approach to its relation to the development of earthquake.

Crustal deformation of seismogenic fault and its surrounding area after the Tangshane arthquake

The fault deformation observed in 18 years after the Tangshan earthquake on the deformation station located on the surface fissure of the seismogenic fault is introduced. The results show that the vertical and horizontal deformations of the seismogenic fault were concentrated within 7 years after the earthquake and the year of 1983 was the turning year of postseismic deformation. The deformation shown by large area levelings is consistent with the intensity level of fault deformation. At present, a relaxation state appears in which stress is not easy for stress to accumulate and there is no probability of stronger earthquake occurrence in the near future.

Response of vertical deformation on faults to remote strong earthquakes

Vertical coseismic deformation on non-causative fault caused by remote strong earthquakes （epicentral distance ≥1 500 km, Ms≥7.0） are observed by fault-monitoring instruments of new type during recent two years. The monitoring result shows, delay time, maximum amplitude and duration of vertical deformation on the non-causative fault have remarkable close relationship with earthquakes magnitude and epicentral distance. The delay time of vertical coseismic deformation have positive linear relationship with epicentral distance. The velocity of coseismic deformation is 5.5 km/s, close to the velocity of surface wave in granite. The logarithms of maximum amplitude of coseismic deformation and epicentral distance have remarkable linear relationship with magnitude. The greater the magnitude and the closer the epicentral distance are, the bigger the maximum amplitude of coseismic deformation on non-causative fault will be. Relative to the epicentral distance, the magnitude is the most important factor to the duration of coseismic vertical deformation on the non-causative fault. Stronger earthquake causes longer vibration duration of coseismic deformation. The experiential equation of co-seismic deformation faults obtained by this work is significant on the coseismic deformation research.

X-ray Peak-Shift Determination of Deformation Fault Probability in Fe-Mn-Si Alloys

The X-ray diffraction peak-shift method was introduced into the determination of deformation fault probability (a) of Fe-Mn-Si alloys with various Mn contents and thermomechanical cycling numbers. The precise lattice constants required were obtained by numerical calculation instead of using standard sample without any fault. The influence of internal stress on the determined a has been evaluated, and the caused relative error was determined as about 4% and thus negligible. The results show that the deformation fault probability increases with decreasing Mn-content and increasing cycle number, which are qualitatively consistent with those results of Psf determined by peak-broadening method.

Static-deformation based fault diagnosis for damping spring of large vibrating screen

Based on the statics theory, a novel and feasible twice-suspended-mass method(TSMM) was proposed to deal with the seldom-studied issue of fault diagnosis for damping springs of large vibrating screen(LVS). With the static balance characteristic of the screen body/surface as well as the deformation compatibility relation of springs considered, static model of the screen surface under a certain load was established to calculate compression deformation of each spring. Accuracy of the model was validated by both an experiment based on the suspended mass method and the properties of the 3D deformation space in a numerical simulation. Furthermore, by adopting the Taylor formula and the control variate method, quantitative relationship between the change of damping spring deformation and the change of spring stiffness, defined as the deformation sensitive coefficient(DSC), was derived mathematically, from which principle of the TSMM for spring fault diagnosis is clarified. In the end, an experiment was carried out and results show that the TSMM is applicable for diagnosing the fault of single spring in a LVS.

Analysis of the Motion and Deformation Characteristics along the Zhangjiakou-Bohai Fault

We have collected GPS data in the period of 1999-2007 from the Crustal Motion Observation Network of China along the Zhangjiakou-Bohai fault and its adjacent regions to study the characteristics of present-day crustal horizontal motion velocities in the research zone.Strain rate components are computed in the spheric coordinate system by the least square collocation method.According to the spatial distribution of the principal strain rate,dilation rate and maximum shear strain rate derived from GPS measurements,this paper analyses the deformation of the subordinary faults of the Zhangjiakou-Bohai fault.The principal compression strain rates are apparently greater than the principal extension strain rates.The larger shear strain rate is mainly in and around the Xianghe,Wenan and Tangshan areas in Hebei Province.According to the profiles across different segments of the Zhangjiakou-Bohai fault,the three segments glong the Zhangjiakou-Bohai fault show an obviously left-lateal strike-slip and compression characteristics.By analysis of the motion characteristics of the blocks,e.g.the Yanshan block,North China Plain block,Ordos block,and Ludong-Huanghai block in and around the North China region,this paper speculates that the dynamics of the motion styles of Zhangjiakou-Bohai fault may directly come from the relative movement between the Yanshan block and the North China plain block,and the ultimate dynamics may be the results of the collison between Indian plate and Eurasian plate,and the persistent northeastward extrusion of the Indian plate.

Gravity changes and surface deformations due to faults with different geometry

Based on the formulae of the gravity changes and surface deformations raised by the dislocation of a point source,the gravity changes and deformations caused by the dislocations of fault with arbitrary geometry are computed by using numerical method. The results show that both of the dislocation and the geometry of the fault plane are the basic elements that determine the gravity and deformation effects. Gravity changes, vertical deformations and apparent vertical deformations induced by the dislocation are alike in their characteristic patterns. The similarities and differences of these patterns provide us a probability in acquiring the gravity and deformation anomalies due to faulting from the observed data. Thus the geometric and kinematic features of the earthquake-generating faults can be appropriately distinguished and evaluated.

Neotectonics around the Ordos Block,North China

The Eurasian continent was subject to multiphase intensive intracontinental deformation in the Cenozoic(Fig.1A).However,its Cenozoic intra-continental deformation process and the driving force has long been disputed,which is only associated with the Indo-Asian collision(Molnar and Tapponnier,1975;Jolivet et al.,1990;Tapponnier et al.,2001;Yin,2010;Xu et al.,2013;Zhao et al.,2016),is caused by the Pacific-Asian collision(Cui,1997;Schellart and Lister,2005;Fan et al.,2019),or is connected with a combined effect of the Indo-Asian collision and the Pacific-Eurasia convergence(Ren et al.,2002;Li et al.,2013;Shi et al.,2015;Liu et al.,2019).

Current tectonic deformation and seismogenic characteristics along the northeast margin of Qinghai -Xizang block

Based on the data from repeated precise leveling and across-fault deformation measurements carried out in recent 30 years and the analyzed results from GPS observations made in recent years along the northeastern margin of Qinghai-Xizang block, and combined with the geological structures and seismic activities, some characteristics in regional tectonic deformation and strong earthquake development are studied and approached preliminarily. The results show that: a) The space-time distribution of current tectonic deformation in this area is inhomogeneous with relatively intensive tectonic deformation in the vicinity of main boundary faults and weak deformation in the farther areas. The intensity of vertical differential movement and the deformation status vary with time, and the horizontal movement and deformation are characterized by apparent compression and strike-slip. b) The tectonic stress field generated by the NE-trending continuous compressive movement of Qinghai-Xizang block due to the northward press and collision of India plate is the principal stress for the tectonic deformation and earthquake development in this area. The evolution of space-time distribution of tectonic deformation and seismicity is closely related to the block activity and dynamic evolution of regional tectonic stress field. c) The vertical deformation uplift and high-gradient deformation zones and the obvious fault deformation anomaly appeared along the boundaries of tectonic blocks can be considered as the indicators of hindered block motion and intensified tectonic stress field for strong earthquake development. Usually, the above-mentioned phenomena would be followed by the seismicity of M6.0, but the earthquake might not occur in the place with the maximum movement. The zones with the fault deformation anomaly characterized by tendencious accumulation acceleration turning and the surrounding areas might be the positions for accumulation of strain energy and development and occurrence of strong earthquakes.

Regional Tectonic Deformation Background and Medium- and Short-Term Precursors to the Minle-Shandan Earthquakes1

Using GPS observations of horizontal movement from 2001 to 2003 and the cross-fault mobile short-levelling data of 1988～2003, and with the aid of the improved negative dislocation model and the time-varying curve of strain intensity ratio of fault deformation, the regional tectonic deformation background and medium- and short-term precursors related to the preparation of the Minle-Shandan earthquakes of M S6.1 and M S5.8 on October 25, 2003 are investigated. The results reveal that, under the background of the wide-range deformation adjustment, short-term relaxation and recovery caused by the Kunlun Mountains earthquake of M S8.1, the hypocenters of the earthquakes are located on the north edge of the shear stress enhancement zone between the compressional locked segments of block boundary fault, a place which may represent an accelerated strain accumulation. An obvious anomaly of strain intensity ratio appeared in short-levelling measurements crossing over the fault at the Shihuiyaokou site, the closest to the epicenters, 3 months before the occurrence of the earthquakes. In addition, the variation in number of anomalies from 10-odd days to months before the earthquakes in the entire monitoring area and the anomaly concentration and local enhancement relative to near source in the 3 months before the earthquakes are regarded to be precursors to the two events.

Simulation by Dislocation Model and Anomaly Property Determination of Huge Leveling Deformation at Linfen Seismic Station

In this study,under the assumption that the two huge leveling deformation anomalies at Linfen seismic station were caused by the Luoyunshan fault( Tumen-Yuli section)movement, we computed the vertical deformation field distribution based on the rectangular fault dislocation model and measured the ground deformation field of the study area using D-InS AR technology. The results are as follows:( 1) Theoretically,the ground vertical deformation field caused by fault movement could be within the elliptical deformation area with the long axis parallel to the fault strike. The largest deformation region is located in the center of the area in the hanging wall of the fault,and the deformation gradually decreases to zero toward the periphery; the impact range induced by the two deformations is respectively as follows: The long axes are about 18 km and26km,the short axes are about 12 km and 17 km and the obvious deformation amplitude is about 1- 3mm and 4- 14 mm.( 2) The measured deformation field by D-InS AR shows that there is no continuous deformation area consistent with the fault strike,and only the presence of land subsidence possibly caused by groundwater excessive exploitation,with the deformation amplitude about 10- 12 mm and 1- 5mm.( 3) The measured deformation field is not consistent with the theoretical result on deformation area and amplitude,which indicates that the fault movement is not the main cause of Linfen huge leveling deformation,but may rather be because of local deformation of the soil layers in the hanging wall of the fault.( 4) By combining the fault dislocation model simulation with the D-InS AR technology measurement,we can determine effectively the nature of the anomalyof the huge cross-fault leveling deformation,thus provide scientific basis for verification of significant leveling anomalies.

Characteristics of block strain and fault movement in the Sichuan-Yunnan region before and after Wenchuan earthquake

Deformation characteristics of the Sichuan-Yunnan region during the two periods 1999--2007 and 2007--2009 are analyzed with a block deformation model and GPS velocity profiles. The results show that the direction of the principal compressive strain rate of the Northwest-Sichuan block - the Mid-Yunnan block - the Southwest-Yunnan block was characterized by a clockwise rotation from north to south. The Anninghe and the Zemuhe faults had some shear-strain accumulation. The southern segment of the Xiaojiang fault had mainly strike-slip movement, while the northern segment was mainly accumulating strain. The 2008 Ms8.0 Wenchuan earthquake had some influence on the mid-southern segment of the Lijiang-Xiaojinhe fault, the Anninghe fault and the Jinshajiang fault, but not the Zemuhe fault, the Xiaojiang fault and the Red River fault as much.

Underestimated seismic hazard in the south of the Issyk-Kul Lake region (northern Tian Shan)

The Tian Shan Mountains were formed in the result of the India-Eurasia collision, which leads to cre- ation of contrast high-mountain relief and world known seismic activity. The seismic catastrophes, recorded instrumentally, have occurred to the north of the Issyk-Kul Lake region. There are also known significant earthquakes with magnitude being about 7 in western and eastern parts of the mentioned lake region. Only in the south of the Issyk-Kul depression the strong earthquakes recorded by the seismic network were not known. Our recent study in the south of the lssyk-Kul Lake region has revealed numerous active tectonic structures related to South Issyk-I（ul Fault： faults and folds, responsible for strong earthquakes＇ occurrence. These were historical and paleoseismic defornlations which led to changes in relief： fault scarps and significant rockslides. We have also found spectacular deformations in archeological monuments. All these deformations testify the location of epicentral areas of two strong historic （about llth and 16th （？） centuries AD） and paleoearthquakes （Holocene and Late Pleistocene）. Magnitude of ancient seismic events, according to parameters of the revealed fault scarps, were Ms 〉 7 and seismic intensity I 〉 IX. All revealed seismic deformations are located to adyrs （piedmonts） of the Terskey Ala-Too range bordered of the lssyk-Kul Lake depression in the south. Their formation is described by the model of a fault which rupture plane becomes shallower southward. This model is complicated by the presence of reverse thrusts. Here, we should admit the existence of a single zone of South lssyk-Kul Fault which is a long-lived feature which separates the structures with the different regime of movements during the Neotectonic time. All obtained data led us to a conclusion of significant underestimation of the seismic hazard in southern lssyk-Kul Lake region.

Microstructure Characteristics of an Fe-Mn-C TWIP Steel After Deformation

The microstructure characteristics of an Fe-Mn-C TWIP steel after deformation are investigated. The results show that the hot-rolled, cold-rolled and then annealed sample of the Fe-Mn-C TWIP steel has excellent mechanical properties, and the true stress-true strain curve from tension tests exhibits repeated serrations. The deformed microstructure exhibits the typical planar glide characteristics such as no cell formation, dislocation pile-ups on a single slip plane, mechanical twins and stacking faults. There are equiaxial and deep dimple structures in the fractograph, indicative of a ductile fracture. Microcracks initiate from inclusions and twin-twin intersections. Deformation and fracture processes are the formation, growth and coalescence of microvoids.

Influence of Temperature on Stacking Fault Energy and Creep Mechanism of a Single Crystal Nickel-based Superalloy

The influence of temperatures on the stacking fault energies and deformation mechanism of a Re- containing single crystal nickel-based superalloy during creep at elevated temperatures was investigated by means of calculating the stacking fault energy of alloy, measuring creep properties and performing contrast analysis of dislocation configuration. The results show that the alloy at 760 ℃ possesses lower stacking fault energy, and the stacking fault of alloy increases with increasing temperature. The defor- mation mechanism of alloy during creep at 760 ℃ is 7＇ phase sheared by 〈110〉 super-dislocations, which may be decomposed to form the configuration of Shockley partials plus super-lattice intrinsic stacking fault, while the deformation mechanism of alloy during creep at 1070 ℃ is the screw or edge super- dislocations shearing into the rafted 7＇ phase. But during creep at 7（50 and 980 ℃, some super- dislocations shearing into 7＇ phase may cross-slip from the {111} to {100} planes to form the K-W locks with non-plane core structure, which may restrain the dislocations slipping to enhance the creep resis- tance of alloy at high temperature. The interaction between the Re and other elements may decrease the diffusion rate of atoms to improve the microstructure stability, which is thought to be the main reason why the K-W locks are to be kept in the Re-containing superalloy during creep at 980 ℃.

Stacking fault energy in some single crystals

The stacking fault energy of single crystals has been reported using the peak shift method.Presently studied all single crystals are grown by using a direct vapor transport（DVT） technique in the laboratory.The structural characterizations of these crystals are made by XRD.Considerable variations are shown in deformation （α） and growth（β） probabilities in single crystals due to off-stoichiometry,which possesses the stacking fault in the single crystal.