The key challenge of PSInSAR(Permanent Scatter Interferometric Synthetic Aperture Radar)lies in the quality of Permanent Scatter(PS)points, which are difficult to extract accurately in fracture zones due to the complex natural ground cover and unique geomorphological environments. In such areas, the inability to reliably extract high-quality PS points limits the application of PSInSAR for monitoring interseismic deformation. To address the problem of high-quality PS point selection in fault zones and improve the effectiveness of PSInSAR technology for monitoring interseismic deformation, this paper presents a comparative study of coherence coefficient and amplitude deviation double thresholds. The study further integrates the Kolmogorov-Smirnov(KS)test and CR homogeneous pixel method, in addition to conventional coherence coefficient point selection techniques. Sentinel-1A SAR images from March 14, 2015, to February 16, 2020, are used as the data source, with the Wushan-Gangu section of the fault zone on the northern edge of the Western Qinling Mountains, near the northeastern edge of the Qinghai-Tibet Plateau, serving as the test area for PSInSAR processing. The quality and reliability of PS point selection using various methods are compared and analyzed.

Two sets of coherence coefficient T_γ and amplitude deviation D_γ double thresholds were tested. The coherence coefficient was set at T_γ=0.5, while the amplitude deviation D_γ was set to 0.5 and 0.3, resulting in 19806 and 2485 PS points, respectively. When the amplitude deviation threshold was lowered, the number of PS points on ridgelines decreased significantly, while there was little change in Gangu County, suggesting poor pixel amplitude stability in mountainous areas. Lowering the threshold eliminated many PS points, retaining only those with high amplitude and stable time series, typically found in hard targets like urban buildings. A KS double sample test was then applied in combination with the double threshold method, with all thresholds coefficient T_γ, amplitude deviation D_γ, and KS test P_γ set at 0.5. This approach yielded 1 313 PS points, showing a significant reduction in PS points on ridgelines and in Gangu County, while urban points became more concentrated on hard targets like buildings. Although the KS test reduced PS points in vegetated areas, it did not fully eliminate noise points. Finally, based on the double threshold results of coherence coefficient T_γ=0.5 and amplitude deviation D_γ=0.3, both the KS test and CR homogeneous pixel selection methods were applied. The CR homogeneous pixel method used a phase difference threshold P_γ=0.5 and a temporal phase stability threshold N_γ=50. This yielded 2 485 PS points for the double threshold method, 133 PS points for the double threshold plus KS test, and 414 PS points for the double threshold plus CR homogeneous pixel method. The latter two methods significantly reduced PS points, with a higher concentration of points in Gangu County, consistent with the expectation that PS points predominantly correspond to hard targets like buildings.

Statistical analysis of the results demonstrated that the combination of the coherence coefficient, amplitude deviation, and CR homogeneous pixel method provided the highest quality PS points, effectively excluding noise points in vegetated areas. The combination of coherence coefficient, amplitude deviation, and KS test ranked second, improving accuracy in urban areas but failing to eliminate noise in vegetated areas. Using Sentinel-1A SAR images and the Wushan-Gangu fault as the test area for time series PSInSAR processing, the accuracy of PS point selection was further verified. A comparative analysis of deformation monitoring results from the three methods revealed that both the KS test and CR homogeneous pixel method improved the accuracy of fault deformation monitoring, with the CR homogeneous pixel method yielding superior results. Monitoring data from 2015 to 2020 showed that the deformation rate of the northern block of the Wushan-Gangu fault ranged from -2 to -0.2mm/a, with an average deformation of approximately -1.7mm/a. In contrast, the southern block exhibited a deformation rate between 0.3 and 0.5mm/a, with an average deformation of about 1.8mm/a The relative average deformation rate between the northern and southern blocks was 0.7mm/a, indicating left-lateral strike-slip movement. Among the three methods, the double threshold plus CR homogeneous pixel method produced PS points with the smallest deformation rate standard deviation, indicating more stable and reliable deformation results.

With the recent development of geodetic observation theory, the increasing satellite platforms and the progress of related technology, InSAR is emerging as a new data source and useful tool for remotely-based geodetic observations. More importantly, InSAR observations play an increasingly irreplaceable role in the field of coseismic deformation observations, earthquake emergency responses, earthquake hazard evaluation and seismogenic structure research. Particularly, InSAR is the most commonly used tool in coseismic deformation measurements on the Qinghai-Tibetan plateau or other global seismic zones, where GPS data are sparse or inaccessible in some cases. Specifically, InSAR measurements help us to respond in time after disastrous earthquakes and provide valuable information associated with how the surface of the crust deforms due to large earthquakes. In the area of scientific research, InSAR provides products of surface deformation observations and serves as model constraints kinematically or dynamically in identifying the buried faults, studying the characteristics of seismogenic faults, obtaining three-dimensional displacements, and investigating the relationship between earthquakes and tectonic structures. InSAR observations and its deformation products have the technical advantages of large spatial scale, high precision and in-time, compared to other geodetic measurements. Consequently, InSAR has the ability to provide scientific and technological support for earthquake emergency observations, and meeting the practical needs of earthquake disaster reduction on the Qinghai-Tibetan plateau.

In this review, we mostly limit our focus to the application of InSAR technology in earthquake cycle deformation monitoring in different structural settings on the Qinghai-Tibetan plateau. We also summarize the InSAR-based studies on fault kinematics and seismogenic structures related to some noted earthquakes on the Qinghai-Tibetan plateau. We highlight how the applications of InSAR data can greatly promote earthquake science and can be used as routine observations in some important areas. Then proceed to discuss the cutting-edge development trend and some new challenges of InSAR technology, which are frequently discussed and investigated, but not well resolved, in recent applications. The endeavors in increasing the precision of small-magnitude deformation measurements and expanding the InSAR data volumes can make the scientific objectives of earthquake disaster reduction on the Qinghai-Tibetan plateau and its surrounding areas feasible and reliable. To better understand how InSAR observations have changed the way we study earthquakes, we summarize the development, commercialization, insights, and existing challenges associated with InSAR coseismic deformation measurements and application in recent two decades.

The reliability of anomaly extracting methods is crucial for pre-seismic thermal anomalies research. However, there is a lack of relevant researches. We compared two commonly used anomaly extracting methods, Z-score(ZS)and Robust satellite technology(RST)method, taking the 2014 Yutian earthquake as a typical example and the 2008 Wenchuan earthquake as a validation. The four aspects of extracted results are compared qualitatively and quantitatively, including the extraction effect, sensitivity to slight change, suppression of background information and indication of seismic information in the actual earthquake case. Moreover, the extracted results of validation case are used to validate the reliability of typical case results. Many intermittent anomalies in surface temperature and outgoing longwave radiation appeared before Yutian earthquake. The frequency of anomalies increases with the proximity of earthquake. The spatial distribution of surface temperature and outgoing longwave radiation anomalies gradually concentrated around the fault zone at the same time. The largest surface temperature and outgoing longwave radiation anomalies occurred one month before Yutian earthquake. The difference between the extraction results of ZS and RST method is mainly manifested in the frequency and amplitude of anomaly changes. The frequency and amplitude of anomaly changes obtained by RST method are higher than those obtained by ZS method. To further explore the reason for these differences, we further evaluate the two methods quantitatively by combining the data of two non-seismic years before and after Yutian earthquake respectively. The sensitivity of anomaly extraction method represents its ability to identify the slight changes of thermal parameters caused by the seismogenic process. The two methods are sensitive to slight changes, but the RST method is better than ZS method. The background information represents normal variation in surface temperature and outgoing longwave radiation caused by non-seismic factors. Suppression of background information determines the accuracy of extraction results. The comparison results show that both methods have certain suppression effect to background information, but the ZS method is better. The spatial distribution of pre-seismic thermal anomalies is an important index for predicting earthquake information(e.g. time of occurrence and location of epicenter). The results of quantitative comparison through normalized distance index show that for surface temperature data, ZS method is slightly better than RST method in indicating the location of epicenter. However, RST method is better for outgoing longwave radiation data. The maximum value of normalized distance index of ZS method occurred closer to the origin time of earthquake. We used the same quantitative evaluation method for the validation earthquake case. The verification results show that in addition to the sensitivity to anomaly changes, the comparison results of the two earthquake examples are similar in terms of the ability to suppress background information and indicate earthquake information. The difference is that ZS method has a better ability to suppress background information and RST method is better in indicating earthquake epicenter in the verification earthquake example. The main reason for the difference in extraction effect between the two methods is that the RST method averages the ground feature classification, and the difference between the observed value and the average value of the classification makes the RST method have a certain amplification effect on the weak signal. The difference between the typical earthquake case and the verification earthquake case is mainly due to the different complexity of the object types in the regions. Based on the above research results, we believe that ZS method and RST method have certain ability to extract pre-seismic anomalies. However, comparatively speaking, the RST method also has a good effect on the extraction of anomalies caused by other factors, and there is uncertainty in the ground feature classification. We believe that ZS method is a more appropriate and simple anomaly extraction method in the general seismic anomaly change extraction.

The seismogenic fault of the Maduo M_S7.4 earthquake in Qinghai Province on May 22, 2021 is not on the conventionally north boundary of the Bayan Har Block, but a secondary fault named Kunlunshankou-Jiangcuo Fault inside the Bayan Har Block which is nearly parallel to the East Kunlun Fault, with a distance of about 70km. As a result, the study on the stress effect of the Maduo earthquake on surrounding faults is urgent, especially on the main boundary faults of the Bayan Har Block, such as the East Kunlun Fault. In this paper, the lithospheric structure of the study area is stratified by using the USTClitho1.0 results of the unified seismic velocity model of the lithosphere in Chinese mainland. The co-seismic slip model of the Maduo earthquake is inversed by the results of InSAR deformation field and precise aftershock location. The model reveals that the coseismic slip of this earthquake is mainly sinistral strike-slip, the fault strike is 276 degrees, the dip angle is 80 degrees, the average rake angle is 4 degrees, the maximum slip is about 5.1m, and the main slip area is mainly concentrated on the depth of 0~15km. By considering the Burgers rheological model which is more consistent with the actual deformation process of lithosphere, the paper calculates the co-seismic Coulomb stresses and viscoelastic Coulomb stresses in the source area and peripheral faults induced by the Maduo earthquake by using PSGRN/PSCMP program.
The results show that, besides the fracture surface of the seismogenic fault, there are three positive co-seismic Coulomb stress change areas on the west and east ends of the seismogenic fault, of which the stress loading area on the west end is oriented toward the northwest of the seismogenic fault, and the other two stress loading areas on the east end are toward the north and east of the seismogenic fault. The positive section of co-seismic Coulomb stress change of the peripheral faults is consistent with the distribution of the source area. The co-seismic Coulomb stress change induced by Maduo earthquake is bigger than 0.01MPa on the near source section of East Kunlun Fault, the east section of Kunzhong Fault, the northwest segment of Gande-Nanyuan Fault and the middle segment of Wudaoliang-Changshagongma Fault. The maximum co-seismic Coulomb stress changes at the depth of 12.5km reach 0.165MPa, 0.022MPa, 0.102MPa and 0.012MPa, respectively, which proves that the Maduo M_S7.4 earthquake has a strong seismic triggering effect on the above faults. By comparison, the impact of Maduo M_S7.4 on co-seismic Coulomb stress change is also positive in the middle section of Longriba Fault, the south section of Xianshuihe Fault and the north section of Longmenshan Fault, but the magnitude is relatively smaller(less than 0.01MPa), in which the co-seismic Coulomb stress change in the middle section of Longriba Fault increases by thousands of Pa, while the co-seismic Coulomb stress change in the south section of Xianshuihe Fault and the north section of Longmenshan Fault increases by only tens to hundreds of Pa.
For the fault sections with co-seismic Coulomb stress change bigger than 0.01MPa mentioned above, their viscoelastic Coulomb stress changes during 50 years are calculated. The results show that the viscoelastic relaxation of lithosphere after the Maduo earthquake further increases the viscoelastic Coulomb stress changes on the above faults, especially the East Kunlun Fault, where the cumulative Coulomb stress will be increased by 0.038MPa after 50 years. The seismic triggering effect of Maduo earthquake on the above faults will continue to increase over time and more attention should be paid to the seismic risk of the above faults in the future.

Due to the ongoing collision between Indian and Eurasian plates, the internal blocks of the Tibet plateau are experiencing eastward extrusion. Resulting from the blocking of the Sichuan Basin along the eastern boundary of the Bayanhar block, the plateau begins to rotate clockwise around the eastern syntaxis, and continues to move toward the IndoChina Peninsula. Such process forms the Hengduan Mountains with thousands of gullies in the Sichuan-Yunnan region, and generates major earthquakes across the entire Red River Fault, where infrastructures and residents are seriously threatened by the frequent earthquakes. InSAR observations feature a high spatial resolution and short intervals, ranging from several days to over a month, depending on the satellite revisit period.
On May 21, 2021, an earthquake struck the Yangbi city. This event provides a rare opportunity to look at the local tectonic and seismic risk in the north of the Red River Fault. We processed the Sentinel-1 SAR data with D-InSAR technology and generated the surface deformation caused by the Yangbi M_S6.4 earthquake occurring on May 21, 2021. Due to the abundant vegetation and moisture in Yunnan, significant atmospheric noise needs to be corrected for the derived InSAR displacement field. The results show a maximum deformation of~0.07m in line-of-sight for ascending track and~0.08m for descending track. The quality of interferogram on the ascending track is low, and only one of the quadrans can be distinguished, the rest of the interferogram is regarded as phase noise. However, the descending interferogram contains two deformation regions, with its long axis roughly along the NW-SE direction. The northeast part of interferogram moves towards the satellite, while the southwest part moves away from the satellite. The InSAR interferograms pattern shows a right-lateral strike-slip movement. Then, we combined coseismic displacement data obtained from the Global Navigation Satellite System(GNSS)and InSAR(both the ascending and descending)to invert the coseismic slip model of the Yangbi earthquake. The inversion test shows that our data cannot give strong constraints for the dip orientations, and the two slip models with opposite dip orientation can explain the observations within the noise level. No matter what the dip orientation is, the slip models show that the coseismic slip concentrated at depth of 2~10km, with a maximum slip of~0.8m, which corresponds to a moment magnitude of M_S6.4, and is consistent with body-wave-based focal mechanism. But the relocated aftershocks in 3 hours immediately after the mainshock reveal a SW-dipping fault plane 10km away to the west of Weixi-Qiaohou-Weishan Fault, we therefore conclude that the Yangbi earthquake ruptured a SW-dipping dextral fault, which is previously unknown. To analyze the effects of the Yangbi earthquake on the seismic risk of the regional dextral faults, we estimated the Coulomb stress change caused by our preferred slip model. The Coulomb stress at 7.5km depth is negative, indicating stress unloading, while the Coulomb stress at 15km depth is positive, indicating slightly loading, but still less than the empirical triggering threshold. The results indicate that Yangbi earthquake partially relieved the strain accumulated on the nearby faults, thus restraining the seismic risk of these faults.

InSAR coseismic deformation fields caused by the Maduo M_W7.3 earthquake occurring on May 22, 2021 were generated using the C-band Sentinel-1A/B SAR images with D-InSAR technology. The spatial characteristics, magnitude of coseismic deformation and segmentation of the seismogenic fault were analyzed. The surface rupture trace was depicted clearly by InSAR observations. In addition, the coseismic slip distribution inversion was carried out constrained by both ascending and descending InSAR deformation fields and relocated aftershocks to understand the characteristics of deep fault slip and geometry of the seismogenic fault. The regional stress disturbance was analyzed based on coseismic Coulomb stress change. The results show that the Maduo M_W7.3 earthquake occurred on a secondary fault within the Bayan Har block which is almost parallel to the main fault trace of the Kunlun Fault. According to field investigation, geological data and InSAR surface rupture traces, the seismogenic fault is confirmed to be the Kunlunshankou-Jiangcuo Fault. The rupture length of seismogenic fault is estimated to be~210km. The NWW direction is followed by the overall displacement field, which indicates a left-lateral strike-slip movement of seismogenic fault. The maximum displacement is about 0.9m in LOS direction observed by both ascending and descending InSAR data. The inversion result denotes that the strike of the seismogenic fault is 276°and the dip angle is 80°. The maximum slip is about 6m and the average rake is 4°. The predicted moment magnitude is M_W7.45, which is overall consistent with the result of GCMT. An obvious slip-concentrated area is located at the depth of 0~10km. The coseismic Coulomb stress change with the East Kunlun Fault as the receiver fault shows that the Maduo earthquake produced obvious stress increase near the eastern segment of the East Kunlun Fault. Thus the seismic risk increases based on the high interseismic strain rate along this segment, which should receive more attention. In addition, the coseismic Coulomb stress change with the Maduo-Gande Fault as the receiving fault indicates that the Maduo earthquake produced an obvious stress drop near the western part of the Maduo-Gande Fault, which indicates that the Maduo earthquake released the Coulomb stress of the Maduo-Gande Fault, and its seismic risk may be greatly reduced. However, there is a stress loading effect in the intersection area of the Maduo-Gande Fault and the Kunlunshankou-Jiangcuo Fault. Considering that aftershocks of Maduo earthquake will release excess energy, the greater earthquake risk may be reduced.

Located at the bend of the northeastern margin of Qinghai-Tibet Plateau, the Haiyuan fault zone is a boundary fault of the stable Alashan block, the stable Ordos block and the active Tibet block, and is the most significant fault zone for the tectonic deformation and strong earthquake activity. In 1920, a M8.5 earthquake occurred in the eastern segment of the fault, causing a surface rupture zone of about 240km. After that, the segment has been in a state of calmness in seismic activity, and no destructive earthquakes of magnitude 6 or above have occurred. Determining the current activity of the Haiyuan fault zone is very important and necessary for the analysis and assessment of its future seismic hazard.
To study activity of the Haiyuan fault zone, the degree of fault coupling and the future seismic hazard, domestic and foreign scholars have carried out a lot of research using geology methods and GPS geodetic techniques, but these methods have certain limitations. The geology method is a traditional classical method of fault activity research, but dislocation measurement can only be performed on a local good fault outcrop. There are a limited number of field measurement points and the observation results are not equally limited depending on the sampling location and sampling method. The distribution of GPS stations is sparse, especially in the near-fault area, there is almost no GPS data. Therefore, the spatial resolution of the deformation field features obtained by GPS is low, and there are certain limitations in the kinematic parameter inversion using this method.
In this study, we obtain the average InSAR line-of-sight deformation field from the Maomaoshan section to the mid-1920s earthquake rupture segment of the Haiyuan earthquake in the period from 2003 to 2010 based on the PSInSAR technique. The results show that there are obvious differences between the slip rates of the two walls of the fault in the north and the south, which are consistent with the motion characteristics of left-lateral strike-slip in the Haiyuan fault zone. Through the analysis of the high-density cross-fault deformation rate profile of the Laohushan segment, it is determined that the creep length is about 19km. Based on the two-dimensional arctangent model, the fault depth and deep slip rate of different locations in the Haiyuan fault zone are obtained. The results show that the slip rate and the locking depth of the LHS segment change significantly from west to east, and the slip rate decreases from west to east, decreasing from 7.6mm/a in the west to 4.5mm/a in the easternmost. The western part of the LHS segment and the middle part are in a locked state. The western part has a locking depth of 4.2~4.4km, and the middle part has a deeper locking depth of 6.9km, while the eastern part is less than 1km, that is, the shallow surface is creeping, and the creep rate is 4.5~4.8mm/a. On the whole, the 1920 earthquake's rupture segment of the Haiyuan fault zone is in a locked state, and both the slip rate and the locking depth are gradually increased from west to east. The slip rate is increased from 3.2mm/a in the western segment to 5.4mm/a in the eastern segment, and the locking depth is increased from 4.8km in the western segment to 7.5km in the eastern segment. The results of this study refine the understanding of the slip rate and the locking depth of the different segments of the Haiyuan fault zone, and provide reference information for the investigation of the strain accumulation state and regional seismic hazard assessment of different sections of the fault zone.

The development of high-rate GNSS seismology and seismic observation methods has provided technical support for acquiring the near-field real-time displacement time series during earthquake. But in practice, the limited number of GNSS continuous stations hardly meets the requirement of near-field quasi-real-time coseismic displacement observation, while the macroseismographs could be an important complement. Compared with high-rate GNSS, macroseismograph has better sensitivity, higher resolution(100~200Hz)and larger dynamic range, and the most importantly, lower cost. However, baseline drift exists in strong-motion data, which limits its widespread use. This paper aims to prove the feasibility and reliability of strong motion data in acquiring seismic displacement sequences, as a supplement to high-rate GNSS.
In this study, we have analyzed the strong-motion data of Wenchuan M_S8.0 earthquake in Longmenshan fault zone, based on the automatic scheme for empirical baseline correction proposed by Wang et al., which fits the uncorrected displacement by polynomial to obtain the fitting parameters, and then the baseline correction is completed in the velocity sequence. Through correction processing and quadratic integration, the static coseismic displacement field and displacement time series are obtained. Comparison of the displacement time series from the strong motions with the result of high-rate GPS shows a good coincidence. We have worked out the coseismic displacement field in the large area of Wenchuan earthquake using GPS data and strong motion data. The coseismic displacement fields calculated from GPS and strong motions are consistent with each other in terms of magnitude, direction and distribution patterns. High-precision coseismic deformation can provide better data constraint for fault slip inversion. To verify the influence of strong-motion data on slip distribution in Wenchuan earthquake, we used strong motion, GPS and InSAR data to estimate the stress drop, moment magnitude and coseismic slip model, and our results agreed with those of the previous studies. In addition, the inversion results of different data are different and complementary to some extent. The use of strong-motion data supplements the slip of the fault in the 180km segment and the 270~300km segment, thus making the inversion results of fault slip more comprehensive.
From this result, we can draw the following conclusions:1)Based on the robust baseline correction method, the use of strong motion data, as an important complement to high-rate GNSS, can obtain reliable surface displacement after the earthquake. 2)The strong motion data provide an effective method to study the coseismic displacement sequence, the surface rupture process and quick seismogenic parameters acquisition. 3)The combination of multiple data can significantly improve the data coverage and give play to the advantages of different data. Therefore, it is suggested to combine multiple data(GPS, strong motion, InSAR, etc.)for joint inversion to improve the stability of fault slip model.

On November 18, 2017, a M_S6.9 earthquake struck Mainling County, Tibet, with a depth of 10km. The earthquake occurred at the eastern Himalaya syntaxis. The Namche Barwan moved northward relative to the Himalayan terrane and was subducted deeply beneath the Lhasa terrane, forming the eastern syntaxis after the collision of the Indian plate and Asian plates. Firstly, this paper uses the far and near field broadband seismic waveform for joint inversion (CAPJoint method)of the earthquake focal mechanism. Two groups of nodal planes are obtained after 1000 times Bootstrap test. The strike, dip and rake of the best solution are calculated to be 302°, 76° and 84° (the nodal plane Ⅰ)and 138°, 27° and 104° (the nodal plane Ⅱ), respectively. This event was captured by interferometric synthetic aperture radar (InSAR)measurements from the Sentinel-1A radar satellite, which provide the opportunity to determine the fault plane, as well as the co-seismic slip distribution, and assess the seismic hazards. The overall trend of the deformation field revealed by InSAR is consistent with the GPS displacement field released by the Gan Wei-Jun's team. Geodesy (InSAR and GPS)observation of the earthquake deformation field shows the northeastern side of the epicenter uplifting and the southwestern side sinking. According to geodetic measurements and the thrust characteristics of fault deformation field, we speculate that the nodal plane Ⅰ is the true rupture plane. Secondly, based on the focal mechanism, we use InSAR data as the constraint to invert for the fine slip distribution on the fault plane. Our best model suggests that the seismogenic fault is a NW-SE striking thrust fault with a high angle. Combined with the slip distribution and aftershocks, we suggest that the earthquake is a high-angle thrust event, which is caused by the NE-dipping thrust beneath the Namche Barwa syntaxis subducted deeply beneath the Lhasa terrane.

The May 12, 2008 M_S7.9 Wenchuan earthquake is ranked as one of the most devastating natural disasters ever occurred in modern Chinese history. The Longmenshan Fault(LMSF) zone is the seismogenic source structure, which consists of three sub-parallel faults, i.e., the Guanxian-Jiangyou Fault(GJF) in the frontal, the Yingxiu-Beichuan Fault(YBF) in the central fault and the Wenchuan-Maowen Fault(WMF) in the back of the LMSF. In this study, geological survey and seismic profiles are used to constrain the faults geometry and medium parameters. Three visco-elastic finite element models of the LMSF with different main faults are established. From the phase of interseismic stress accumulation to coseismic stress release and postseismic adjustment, the Wenchuan earthquake is simulated using Continuous-Discrete Element Method(CDEM). Modeling results show that before the 2008 Wenchuan earthquake, the GJF becomes unstable due to the interaction between its unique fault geometry and the tectonic stress loading. In the fault geometry model, the GJF is the most gently dipped fault among the three faults, which in return makes it having the smallest normal stress and the greatest shear stress. The continuous shear stress loading finally meets the fault failure criteria and the Wenchuan earthquake starts to initiate on the GJF at the depth of 15~20km. The earthquake rupture then propagated to the YBF. At the same time, due to the GJF and YBF rupture, the interseismic stress accumulation has been greatly reduced, causing the WMF failed to rupture. Although the stress accumulation in the WMF has been reduced significantly after the earthquake, yet it has not been released completely, which means that the WMF likely has with high seismic risk after the 2008 Wenchuan earthquake. We also find that the stress perturbation caused by gently dipping segment of the fault can promote the passive rupture in the steeply dipping segment, making the upper limit of dip angles larger than traditional assumption.

This study focuses on four moderate-sized earthquakes in the northern margin of the Qaidam Basin, northeastern Tibet Plateau, China, of which one occurred in 2008, and three in 2009, respectively. We obtain coseismic displacement fields of these four events using Envisat descending ASAR data and D-InSAR technology. The results show that the 2008 earthquake has only one deformation center and the 2009 earthquakes have three deformation centers in their fields. The maximum displacement of 2008 and 2009 earthquakes are 0.097m and 0.41m in the LOS(line of sight), respectively. We invert ground displacements of these earthquakes based on elastic dislocation models to estimate slip distribution on fault planes. For the 2008 event, using a one-segment fault model, the inversion reveals peak slip of about 0.47m occurring at a depth of 19km. For the 2009 earthquakes, the ground displacement pattern observed by InSAR can be fitted by a three-segment fault model with smallest RMS of residuals. The three sectional fault model is considered the most reliable.

We achieved the coseismic displacements of the Napa M_W6.1 earthquake located in California US occurring on 24 August 2014 by using InSAR data from the newly launched ESA's Sentinel-1A satellite. The 30m×30m ASTER GDEM was used to remove the terrain effect, and phase unwrapping method of branch-cut algorithm was adopted. In order to obtain a better coseismic displacement field, we also tested 90m×90m SRTM data to remove the terrain effect and Minimum Cost Flow algorithm to unwrap the phase. Results showed that the earthquake caused a significant ground displacement with maximum uplift and subsidence of 0.1m and -0.09m in the satellite light of sight(LOS). Based on the Sentinel-1A dataset and sensitivity based iterative fitting(SBIF) method of restrictive least-squares algorithm, we obtained coseismic fault slip distribution and part of the earthquake source parameters. Inversion results show that the strike angle is 341.3°, the dip angle is 80°, rupture is given right-lateral fault, average rake angle is -176.38°, and the maximum slip is ~0.8m at a depth of 4.43km. The accumulative seismic moment is up to 1.6×10¹⁸N·m, equivalent to a magnitude of M_W6.14.

Earthquake prediction is one of the key areas of earthquake research. Thermal infrared abnormity, which is the abnormally increased land surface temperature, is universal before earthquake and has complex nonlinear relation with the three elements of earthquake. Combining the advantage of neural network, this paper provides a method for earthquake prediction by taking thermal anomaly as information source and constructing a neural network to carry out the test. Based on the MODIS data which has synthesis of eight days with 1km resolution, taking a 10°×10° rectangle, whose center is the epicenter, as research area, and a two-month time before earthquake as the time range, we used RST algorithm to extract thermal anomaly information before earthquake. Considering the time-space relationship between thermal anomaly information and the fault zone, thinking carefully about the information of the neural network input neurons, we constructed BP neural network and used 100 earthquake cases with magnitudes larger than 5, and 70 random samples without earthquake in the research region for training and simulating. According to the statistical analysis, the prediction accuracy is 80%, missing prediction rate is 20%, and false prediction rate is 13.3%. Prediction accuracy of magnitude with error within magnitudes of 2 is 69%, prediction accuracy of earthquake origin time with error within 30 days is 87.5%, and prediction accuracy of epicenter location with error within 3°is 81.2%. The result shows that BP neural network-based earthquake prediction is feasible by using thermal infrared abnormal precursor extracted by RST method. However, in this experiment, the determination of the start time of thermal abnormity, the origin point and range of research area are based on the known epicenter location and time. In fact, the result depicts a non-linear relationship between earthquake and thermal abnormity, and the accuracy of prediction reflects the correlation degree. Therefore, the prediction accuracy of future earthquake may be not as large as our result. For future earthquake prediction, accurate selection of research area and neuron number of hidden layer in neural network has great influence on prediction result.

The variance component estimation method (VCEM) in generalized surveying adjustment theory, which realizes optimal weights allocation for different data sources, is applied to jointly invert two independent datasets, InSAR and GPS, for 3-D deformation field acquisition in this paper. Illustrated by the case of the Wenchuan earthquake, 3-D deformation field in high coherent area near the fault is achieved by using this method, which shows clearly a whole picture for the locations of right-lateral and thrust components movements generated by the earthquake. The 3-D deformation results are quantitatively consistent with GPS observations with RMS errors less than 5cm in 3-D directions, which demonstrates the feasibility to acquire precise 3-D deformation field by employing VCEM to fuse independent deformation datasets.

Consisting of three water diversion projects, i.e. Western Route Project(WRP), Middle Route Project(MRP)and Eastern Route Project(ERP), South-to-North Water Diversion Project is by far the world's largest water conservancy project. It is also a major strategic infrastructure to optimize the allocation of water resources in China.
The MRP has a total length of 1267km, including a canal segment of 731km long located in Henan Province, which accounts for more than half of the total mileage and runs through from north to south the central plains of China. The project starts mainly in the north of Henan Province, running through Hebi mining area(i.e. Hebi Coal Industry Group Co. Ltd.), Tangyin graben, three cities(i.e. Weihui, Hebi and Anyang city)and two counties(i.e. Qixian county and Tangyin county). Being threatened by mining subsidence, regional tectonic activities and urban groundwater subsidence, its embankment is prone to instability.
In order to assess the stability of embankment along the route, and also to provide safety guarantee for the water diversion project, with the case of the north Henan section of Middle Route Project(MRP), all 9 periods of ENVISAT ASAR data of 2009 are processed by means of 2 PASS plus external DEM D-InSAR processing algorithm, the parameters of space-time baseline are analyzed, best optimal interferometry images pairs are selected, and D-InSAR processing strategies are optimized to obtain differential interferograms for 33 monitoring points along 127km route; information of subsidence area, urban surface settlement area, as well as the amplitudes due to groundwater mining is extracted, and thematic maps of interferometric phase change vectors are gotten.
The following understandings are obtained: 1)There is uneven subsidence over the diversion canal. The cumulative minimum amount of subsidence is -33mm, and maximum subsidence is -73mm in 350 days. Annual subsidence rate is between 0.34m/yr to 0.76m/yr, and annual average subsidence rate is 0.53m/yr. In general, subsidence of monitoring points fits with exponential distribution, with the average correlation coefficient R²=0.7418. According to some mathematical models of curve fitting for monitoring point subsidence, it can be predicted that the subsidence of embankment of water diversion canal tends to be stable in majority of the sections. At the same time, both subsidence value and rate are getting smaller. 2)This study shows that due to combined effect from a variety of factors, this region has a poor regional geological stability. Analysis reveals that tectonic activity and urban surface subsidence are the main influencing factors, infrastructure construction is the secondary effect on the embankment stability, and there is no direct correlation with mining subsidence.

In the past few years, the improved InSAR technology based on time series analyses to many SAR images has been used for measurement of interseismic deformation along active fault. In the paper, we first made a summary and introduction to the basic principle and technical characteristics of existing Time Series InSAR methods(such as Stacking, PSInSAR, SBAS). Then we presented a case study on the central segment of Haiyuan Fault in west China. We attempt to use the PS-InSAR(Permanent Scatter InSAR)technique to estimate the motion rate fields of this fault. We processed and analyzed 17 scenes of ENVISAT/ASAR images in descending orbits from 2003-2010 using the PS-InSAR method. The results reveal the whole movement pattern around the Haiyuan Fault and a remarkable velocity gradient of about 5mm/a across the central segment of the fault. The motion scenes are consistent with left-lateral strike-slip. On this basis, we make a discussion on some issues about observation of fault activity using Time Series InSAR methods, such as the changes of LOS deformation rates with fault strike and region width observed across a fault, fault reciprocity and motion style indicated by Time Series InSAR rate map and the relationship between the InSAR LOS deformation and the ones from other methods. All these studies will benefit the promotion of InSAR application in detection of tectonic movement.

Vertical coseisimic deformation near seismogenic fault is one of the most important parameters for understanding the fault behavior, especially for thrust or normal fault, since near field vertical deformation provides meaningful information for understanding the rupture characteristics of the seismogenic fault and focal mechanism. Taking Wenchuan thrust earthquake for an example, we interpolate GPS horizontal observed deformation using Biharmonic spline interpolation and derive them into east-westward or north-southward deformation field. We first use reliable GPS observed value to correct InSAR reference point and unify both GPS and InSAR coordinate frame. We then make a profile using InSAR data and compare it to that from GPS data and we find GPS and InSAR observation reference point has a 9.93cm difference in the hanging wall side, and around -11.49cm in the footwall. After correction, we obtain a continuous vertical deformation field of the Wenchuan earthquake by combined calculation of GPS and InSAR LOS deformation field. The results show that the vertical deformation of both hanging wall and foot wall of the fault decreases rapidly, with deformation greater than 30cm within 50km across the fault zone. The uneven distribution of the vertical deformation has some peak values at near fault, mainly distributed at the southern section(the town of Yingxiu), the middle(Beichuan)and the northern end(Qingchuan)of the seismogenic fault. These three segments have their own characteristics. The southern section of the fault has an obvious asymmetric feature, which exhibits dramatic uplift reaching 550cm on the hanging wall, with the maximum uplift area located in Yingxiu town to Lianshanping. The middle section shows a strong anti-symmetric feature, with one side uplifting and the other subsiding. The largest uplifting of the southern segment reaches around 255cm, located at the east of Chaping, and the largest subsiding is in Yongqing, reaching around -215cm. The vertical deformation of the northern section is relatively small and distributed symmetrically mainly in the north of Qingchuan, with the maximum uplift to be 120cm, locating in the northernmost of the seismogenic fault.

Differential Synthetic Aperture Radar Interferometry (D-InSAR) is a newly developed technique for monitoring large-scale ground deformation with some prominent advantages such as high accuracy and pantoscopic view. The vertical crustal deformation accuracy can be measured by D-InSAR technology to the millimeter level, but due to restrictions of spatial, temporal decorrelation and atmospheric delay, the application to the monitoring of the crust long-term slow deformation is limited. The Permanent Scatterers approach, which is based on conventional InSAR technique, puts emphasis on processing time series of SAR interferograms by recognizing and analyzing single scatterers with a stable backscatter intensity or reliable phase behavior in time, to study the deformation histories of the earth's surface in a long time series. The PS approach can better conquer problems of temporal and spatial decorrelation, also the atmospheric delay effect, which will improve the efficiency of datum utilization when measuring large time scale deformation events. The PS-InSAR, as an innovation of D-InSAR technology, can overcome the loss of coherence time, and meanwhile, calculate and eliminate the atmospheric effects to ensure the normal operation of the interferometric processing. It acquires the accumulated deformation and its rates at the coherent points in the images.
In this paper, the basic principle, advantage and status of PS-InSAR are introduced. The slight deformation of Gangu area in the fault zone along the north fringe of west Qinling Mountains which is one of the major left-lateral strike-slip active faults in northeastern margin of Tibetan plateau is monitored by PS-InSAR technology using 14 scenes of ENVISAT ASAR data from May 2008 to September 2010. The result shows that the rate of the north wall of the fault zone is -1～-2mm/a, the rate of the south wall of the fault is 3～4mm/a, and relative slip rate between the two walls of the fault zone in Gangu area along the north fringe of west Qinling Mountains is approximately 5mm/a; the points target deformation rate and deformation direction both match with the left-lateral motion feature of the north fringe fault zone of west Qinling Mountains, and results have a good agreement with the study results by other scholars. This suggests that the PS-InSAR technology is capable of detecting crustal small deformation.

The distribution and characteristic of ground deformation is a key issue in geodesy,which brings insight into the geometry of the ruptured fault and seismic hazard assessment in the future in the surrounding areas. It also provides better constraint conditions for geophysical inversion. Compared with field research,satellite imagery regularly provides detailed and spatially comprehensive images and is a most valuable alternative especially for the study in remote areas. So,observing seismic rupture is urgent after earthquake. InSAR is useful for measuring ground displacement,but the technique has severe limitations that are mainly due to data decorrelation and signal saturation,and it does not generally provide measurements in the near-fault area where large displacements occur. In this paper,the sub-pixel correlation method and SPOT image are used to map the Wenchuan earthquake rupture and to identify the faults activated by the earthquake. A computation is introduced of the inverse projection matrices for which a rigorous resampling is proposed. Image registration and correlation is achieved with an iterative unbiased processor that estimates the phase plane in the Fourier domain for subpixel shift detection,then the earthquake deformation field is derived.The results indicate that the Wenchuan earthquake produced at least surface ruptures on two faults along the Longmenshan Fault,the main rupture named Beichuan-Yinxiu rupture zone(Longmenshan town-Gaochuan in this map)and the secondary rupture named Hanwang rupture zone.The former is characterized by dextral-slip thrusting with a horizontal displacement of 4～6m in average and a dextral-slip displacement of 1～3m near Gaochuan town.The latter is characterized by pure thrusting,with horizontal displacement 1～2m in average. There is no obvious ground rupture along Wenchuan-Maoxian Fault.The research indicates that sub-pixel correlation using optical image can be a powerful complement to differential radar interferometry,which can measure ground displacement near the fault zone.The study also shows that earthquake displacement fields can be calculated by remote sensing technology.The surface rupture can be traced and the meizoseismal area can be located by this method. Compared with field research,satellite imagery regularly provides detailed and spatially comprehensive images and is a most valuable alternative especially for the study in remote areas.

The interferometric baseline is a vital parameter in the InSAR technique,which determines the correlation between two repeat-pass images and imposes direct effect on the accuracy and reliability of the mapping result. If the baseline is not accurately estimated,the residual phases from the orbit and topography will be left in the expected phase of deformation leading to errors of the final result. In this work,we analyze the influences of the baseline on the reference phase and simulated topography phase,and present several methods of interferometric baseline estimation. Then we study the mapping process of the coseismic and post-seismic deformation of the 1997 Mani,Tibet M7.7 earthquake based on the 8-sence ERS2-SAR data and InSAR.Our attention is focused on comparison of interferograms under varied conditions for baseline estimations,such as rough orbit data,precise orbit data,frequency of interferometric fringes and control points on the ground. The result shows that when the baseline is estimated by rough orbit data,the yielded differential interferograms contain considerable phases of orbit residuals which make fringes dense and deformation enlarged. Thus we must use the precise orbit data for baseline estimation. Sometimes,however,the influence of the orbit cannot be removed completely even if we employ precise orbit data. In this case we should make further corrections,including removing superfluous fringes based on interferometric fringes frequency and baseline correction using the control points on the ground. With these improvements,the resultant coseismic displacement along the fault of the Mani earthquake is 4.5m. The post-seismic deformation by this event is concentrated in a narrow 10～20km-long zone around the fault. The accumulated fault slip 508 days after the main shock reaches at least 5.6m,which continues to grow with time. These analysis results are consistent with the field observations,meaning the improvement method presented in this paper is effective.

Because the seismic data is so various and is continuously increasing in number,sharing seismic data and providing data service is more difficult.This paper proposes a method to optimize the existing seismic data model based on the modeling tool of PowerDesigner.The method was initially applied to the exiting 1/4000000 active fault GIS database.Aimed at the actual problem of active fault GIS database,the method realizes the optimization of fault data model.And the optimized fault database was applied to specific example cases.Meanwhile,comparative analysis was done between the optimized PDM with the old one.The result shows that the optimized model is more flexible and convenient to use,the data description is more accurate,the relationship between data is clearer,and the data constraint is more standard and complete. It can meet the different needs of seismologists.The proposed optimization method for earthquake data model has a certain value of popularization and application,and it lays a good foundation for seismic data sharing and data service in the future.

We used the radar data from the satellite ALOS/PALSAR of Japan and the differential interferometric synthetic aperture radar(D-InSAR)technology to derive the coseismic displacement field produced by the M_S 8.0 Wenchuan,Sichucan Province,China earthquake on 12 May 2008.Based on processing SAR data of 7 tracks and 112 scenes by the two-pass method,we obtained the interferometric map of 450km×450km covering the causative fault and determined the distribution range of incoherent zones.Proper phase unwrapping was performed to these tracks of continuous and discontinuous phases,yielding digital image of the interferometric displacement field,which is analyzed by displacement contours and the profile across the fault.The result shows that the Wenchuan M_S 8.0 earthquake has produced a vast area of surface deformation along the Yingxiu-Beichuan Fault,primarily concentrated in a near-field range of 100km wide on the both sides of the causative fault.In this field,the 250km-long and 15～35km wide incoherent zone nearby the fault has suffered the largest deformation with surface ruptures,of which the amount is too large to measure by InSAR.The secondary deformed areas are 70km wide on each side of the incoherent zone,where envelope-like fringes are clear,continuous and converging towards the fault,indicative of increasing gradient and amplitude of displacements which exhibit sunk north wall and uplifted south wall in sight line.With respect to the north and south edges of the data track,the maximum subsidence in the north wall is 110～120cm appearing northeast of Wenhcuan and Maoxian,and a big range of descents of 55～60cm occurred nearby the epicenter south of Lixian.The largest uplift 120～135cm in the south wall is present at the epicenter west of Yingxiu,north to Dujiangyan and around Beichuan.The maximum relative displacement between the north and south walls is up to 240cm that appears nearby the epicenter west of Yingxiu and north to Dujiangyan.In the far-field 70km away from the incoherent zones on the both sides of the causative fault,there are sparse fringes indicative of displacements less than 10cm.The profile across the fault indicates a highly variable gradient of deformation with profound heterogeneity near the fault and in its hanging wall,and a relatively uniform deformation in the foot wall.These differences of deformation can be attributed to complicated thrust faulting.Our analysis suggests that the fault rupture of the Wenchuan earthquake is a relative thrust between the two walls of the fault.

Using D-InSAR technology and by processing 7 track 56 scenes ALOS/PALSAR data,the surface deformation field of Wenchuan,Sichuan earthquake on May 12,2008 has been extracted.The deformation field covers a 500km?450km area and crosses Jinchuan-Shimian,Heishui-Leshan,Songpan-Pengshan,Nanping-Jianyang,and Kangxian-Chongqing regions,including the severely earthquake-hit areas,such as Lixian,Wenchuan,Maoxian,Beichuan,Qingchuan,and so on.The results show that the deformation field scope is large and the Sichuan basin has been deformed to different degrees.The incoherent belt near earthquake fault shows that the main earthquake surface rupture zone is on the Beichuan-Yingxiu Fault zone.The trackable surface rupture zone runs from the southwest of Yingxiu near the macroscopic epicenter to the north of Suhe in Qingchuan county,about 230km long.The southwest section of the seismogenic fault from Wenchuan to Maoxian shows an incoherent band width obviously larger than that of other incoherent parts,which is closely related to the surface rupture from Dujiangyan to Anxian on the Pengxian-Guanxian Fault(the Mountain Front Fault),and this surface rupture zone is about 70km long.Away from the seismic fault region,the northwest wall of the fault uplifted and the southeast wall subsided.However,both walls in the vicinity of the seismic fault uplifted locally,and along the fault the distribution is very uneven,showing strong segmentation,which indicates the fault is characterized by reverse thrust.The differences of epicentral positions and earthquake origin time given by Harvard,USGS,NEIC,CENC also show that the Wenchuan earthquake rupture process is a multi-point breakdown process.The largest relative deformation amounting to 260cm occurred in the epicentral region on the west of Yingxiu;if converted into vertical deformation,the relative vertical deformation of the two regions is up to 3.3m.In Ya'an and Emei mountain area,the settlement is about 35cm.In Chongqing and to its south,there is about 25cm small-scale uplift.

Based on ArcGIS and MapInfo software,we digitized the active tectonic map(1:4000000)of China,which was compiled and revised by Academician Deng Qidong,and built the spatial database of active tectonics of China. The database integrates rich active tectonic data,such as earthquake catalogue with magnitude above 6,active faults,the Quaternary basins,active folds and their associated attribute parameters,and implements the scientific and effective management to these active tectonic data. At the same time,the spatial database joins the spatial map data and its associated attribute data together,which implements the data query between spatial feature and its attribute parameters and also makes it possible to do spatial analysis with different data layers. These provide much convenience for earthquake study and engineering construction institutions to use these data in practical application.

The paper first summarizes the advances in detection of volcano activity using satellite thermal infrared remote sensing and discusses the feasibility and means to monitor the thermal anomaly caused by volcano activities through satellite thermal infrared remote sensing technology. Then, some applied methods are put forward to remove the influences of geological environments and meteorological variation on earth surface thermal infrared radiation for extracting volcanic thermal anomaly. These methods include getting rid of the influences of ground environment factors, such as terrain, vegetation and rock types by establishing brightness temperature variation models of volcanic region and eliminating the influences of weather by difference calculation of brightness temperature between volcanic region and adjacent contrast region. Finally, the paper gives a study case of Changbai Mountains volcano. By using NOAA AVHRR data of the three years of 1999, 2003 and 2004, the authors analyzed and interpreted the thermal infrared brightness temperature images of Changbai mountain volcano region, and calculated the annual variations of brightness temperature of Changbai Mountains Tianchi Lake and adjacent contrast region. The result shows that the spatial distribution of brightness temperature in Changbai mountains volcano area is mainly controlled by hypsography and physiognomy, and presents a “tundish” shape. From Tianchi Lake to its peripheral places, the brightness temperature increases gradually, but the Tianchi Lake is a clear hot spot in cold background. The temporal variation of brightness temperature in this region is mainly influenced by seasons and presents seasonally changeable characteristics. The comparison analyses of annual variations of brightness temperature between Tianchi Lake and contrast region reveal that the brightness temperature of Tianchi Lake in 2003 and 2004 increased markedly with a magnitude about 2K compared with that in 1999. We suppose this elevated temperature is likely to be a reflection of increasing activity of Tianchi volcano in recent years. Furthermore, this result is consistent with that obtained by Changbai Mountains Tianchi Volcano Observatory in the past 4 years. These indicate that the satellite thermal infrared remote sensing is a feasible and effective measure for detecting volcano activity, and its application in detection of volcano activity deserves more detailed research.

Geographic Information System (GIS) technique provides a powerful tool for managing,manipulating,analyzing and displaying space related data set. The compilation of seismic zoning map requires a vast amount of spatially referenced data. Therefore,the application of GIS to the seismic zo￣ning work allows the users to take advantage of various functions of GIS into the seismic zoning work. This paper introduces briefly the procedure and results of GIS application in the compilation of the New Seismic Zoning Map of China (2001). The GIS Database of the New Seismic Zoning Map includes three sub-databases: 1. Sub-database for seismic environment and potential seismic sources,including: (1)Earthquake catalog; (2)Quaternary active faults; (3)Cenozoic basins; (4)Earthquake mechanism; (5)Geophysical anomalies and deep structure; (6)Seismotectonic provinces and zones; (7)Potential seismic sources. 2. Sub-database for earthquake ground motion and seismic attenuation,including: (1)Seismic intensity and isoseism; (2)Observed seismic intensity; (3)Strong ground motion. 3. Sub-database for the results of probability calculation of seismic parameters.

Some researchers believe that satellite thermal infrared anomaly before earthquake is related to gas releasing of the earth. Accordingly,whether the gas releasing phenomena can be observed by satellite thermal infrared remote sensing becomes a key problem. In this paper,two sites where gas releasing phenomena of the Earth occurred assuredly were selected for the study of this key problem. One is the Kaixian County where high pressure and high concentration gas blow-out event of the No.16 oil well took place,and the other is around the epicenter of the west of Kunlunshan Pass M_S8.1 earthquake where gas releasing has been observed to continuously occur along the Kunlunshan Fault even one year after the earthquake. The characteristic features of satellite thermal infrared images before and after gas releasing process have been analyzed,and the thermal infrared anomaly related to gas releasing or gas blow-out has been identified. Furthermore,the feasibility to observe gas releasing phenomena by satellite thermal infrared was discussed. The result shows that the gases blew out from the oil well and the fire from ignited gases are distinctly reflected on satellite thermal infrared images,but the gas releasing phenomena along the Kunlunshan Fault after the M_S8.1 earthquake are poorly displayed on thermal infrared image,so that the infrared thermal anomaly related to gas releasing along this fault is difficult to be recognized by visual interpretation. The comparison of brightness temperature,however,has revealed that the brightness temperature in the gas releasing sites along the fault is higher than that of the surrounding areas either before or after the earthquake.

The basic principle and method of crustal stress measurement by borehole breakouts are introduced in this paper,and some problems in determining the direction of the horizontal principal stresses from the shear rupture of the borehole walls are discussed.Several thousand groups of data obtained from the logs of four-arm dipmeter of 15 oil wells in Damintun depression of Liaohe oil field were collected.Basing on the statistics and analyses of these data,we calculate the predominant direction of the long axes of borehole breakout ellipses in each oil well at different depths in order to reveal the variation of the principal stress directions with depth.On the basis of the predominant directions of the long axes of borehole breakout ellipses,we calculate and acquire the predominant directions of the maximum horizontal principal stress at different depths for all15oil wells.The results show that the predominant direction of the long axes of the borehole breakout ellipses is about N10°W—N10°E,while the predominant direction of the maximum horizontal principal stress is about N80°～100°E,with a mean of N90°E and a general trend of NEE.This conclusion coincides well with the values obtained from focal mechanism solutions.The variation of the predominant direction of the maximum horizontal principal stress with depth is relatively small,about10°～15°.This may indicate that the direction of modern tectonic stress field in Damintun depression of Liaohe oil field is stable and is possibly controlled by the same tectonic stress field.

An engineering seismological WebGIS application system (ESWebGIS) is established in this paper by using GIS software Component MO/MOIMS. The system implements the sharing of spatial data and GIS applications and greatly promotes the percentage of utilization of spatial information and GIS applications for engineering seismological studies. Users can easily browse, search, analyse and use the engineering seismological spatial information from Internet just like on their local computers, and they can also download the needed data to their local machines for use in their locally installed GIS software. The ESWebGIS system adopts the popular three layer Browser/Server architecture and thin client/fat server model. Development tools, spatial database and WebGIS applications are all installed and running on a remote map server. All client requests are submitted to the map server for processing, no need to download or install the GIS components on client computers. This model is very convenient for users to use. The GIS components MO/MOIMS, JavaScript, VB6.0, HTML and Oracle8i etc. are used to develop the ESWebGIS. The program modules of ESWebGIS are divided into basic GIS function modules and engineering seismology application modules. The basic GIS function modules, such as map's zoom out, zoom in, pan, overlay, point query, layer moving, active layer locating and labeling are programmed by using MO/VB. These modules are commonly needed for any GIS application system and not limited to a specific database or project. They can be freely called by any GIS application. Engineering seismology application modules, which serve the engineering seismology studies, are designed and coded according to the GIS database constructed for engineering seismology. The spatial data that can be shared through ESWebGIS system have been collected and input into GIS database. The commercial GIS software MapInfo5.0 is used for the database's construction.To improve the system's performance, some effective measures, such as detailed delamination of spatial objects, reasonable organization and logic classification of database, multilevel display scales, and data partition index based on grid have been taken to increase the transmission and display speed of maps on Internet. These improvements make it possible that a great number of map layers with different scales are quickly displayed, overlayed and dynamically integrated on Internet. The running results of ESWebGIS indicate that these measures are effective. In addition, a method called agent index preprocess is used to achieve the interoperability between GIS data with different formats coming from different remote database servers. The ESWebGIS realizes the upgrading of GIS to networking environment, and it can be used to fulfill the following tasks: (1) To browse, draw and manage maps on Internet; (2) To perform attribute query and spatial query of maps; (3) To perform spatial analysis and statistical analysis; (4) To upload and download spatial data files onto/from GIS map server; (5) To publish any GIS data by using Common map browser; (6) To remotely update the spatial data of GIS database on GIS map server; (7) To manage the users and to make the system secure. The ESWebGIS is really an interactive On line GIS system, which is open to global Internet users, and is not limited to certain region. It will greatly enhance the sharing and using efficiency of spatial data.