In this paper, general monitoring conditions of water temperature in our country and micro-behavior phenomena such as solid tide, co-seismic effect and precursory anomaly before earthquakes is introduced. And its mechanism is analyzed. The authors propose that the study of mechanism of water behavior should be carried out from some aspects, such as heat systems and heat process, for example, from two geotemperature gradients, two heat convections, one conductivity and one heat diffusion and so on.

DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite, the first electromagnetic satellite specially aiming to earthquake monitoring in the world, was launched in 2004 by France, and ended in the end of 2010, with operating time of 6.5 years. The data along more than 30000 orbits were obtained, which provided a solid data foundation for the research in earthquake monitoring and ionospheric physics. Scientists in many countries carried out a number of earthquake application studies by using the data from this satellite, with hundreds of paper published, and pushed the research in seismo-electromagnetic satellite to a new peak. CSES (China Seismo-Electromagnetic Satellite), the first space satellite for geophysical field detection in China, was successfully launched on February 2, 2018. At present, its in-situ commission has been finished, and the satellite has been put into service, with the scientific data released to the public officially. Under this condition, it is important to summarize and retrospect the improvement and achievements in technology and science from DEMETER, in order to maximize the effectiveness of CSES, and transform the space electromagnetic detection to the operational run in earthquake investigation. The remarkable progresses from DEMETER satellite will be introduced in this paper, and the future development domains are suggested in space electromagnetic detection technology and scientific research combined with the characteristics in CSES satellite.

We first describe chemical and geochemical characteristics of hydrogen, as well as relations between hydrogen soil vapor concentrations and earthquake events. And then we discusse the possibility of using hydrogen soil vapor monitoring in the vicinity of fault zones to make short/immediate earthquake prediction. Hydrogen (H) is an element with the smallest particle size, the lightest weight, the fastest speed and the most powerful penetration ability. The concentration of hydrogen (H₂) in the atmosphere is very low, only 0.5 ppm. But it is higher in the crust, approximately n～nx10² ppm, which is mainly located at a depth ranging from 5 to 8 km, especially in the fault zones. There are good correlations between Hydrogen concentrations and seismic activities. Noticeable changes of hydrogen concentrations can normally be observed several to tens of days before an earthquake, and the ratio of signal to noise is very high. Recently, the successful development of a new digital hydrogen detecting instrument (ATG-6118H) makes continuous monitoring of hydrogen possible. We present some experimental observation results and propose to establish a large scale hydrogen monitoring network along some fault zones.

With the fast development of global industrialization, high-voltage power lines have become one of the man-made interferences in electromagnetic environment monitoring. In this paper, recent achievements on power line radiations have been summarized, especially by using the satellite electromagnetic observations from DEMETER, such as power line harmonic radiation (PLHR), magnetospheric line radiation (MLR), ELF/VLF emissions, high energetic particle precipitation, etc. And then the coupling models including electromagnetic wave propagation and nonlinear wave-particle interaction have been introduced and discussed. It is aimed to provide more information for the data processing and analyzing techniques in the upcoming China Seismo-Electromagnetic Satellite (CSES-1) mission when the same PLHR signals are dealt with or the weak earthquake-related disturbances are distinguished.

The East Kunlun fault zones are located in the northern margin of the Bayanhar block. Investigation of earthquake rupture behaviors of these fault zones is helpful for future seismic risk estimation for northwest Sichuan. We carried out a number of field geological investigation, typical micro-topography DGPS measurement and sample dating. Our results show that earthquake activities of the East Kunlun fault zones extend to the north bound of the Zoige basin. This part has been named Luocha segment, which belonged to the Tazang fault. Satellite images for Luocha segment are clear on the gray strips. The earthquake rupture zones are represented mainly by fault scarp, slope in the valley, gully and terraces dislocation, plant distribution in linear, plunge, fault springs, broken plug pond, landslide, collapsed and talus. These phenomena are distributed along the fault and formed an ~50 km long inverse “L-shaped” deformation strip. Fault activities produced gullies and left movement of terraces. Horizontal dislocations are in the range of 5.5~6 m, 18~23 m, 68~75 m, 200~220 m respectively. An earthquake happened recently between 340±30～500±30 BP, its macro-epicenter was located 5~7 kms northwest from the Benduo village, magnitude M_W7.3~7.4, with a maximum of 6 m coseismic displacement, horizontal dislocation 5.5~6 m, vertical dislocation 0.2~0.5 m. These phenomena show that the Tazang fault was the causative fault of the earthquake and raptured in Holocene. The fault has been controlled by compressive shear recently and shows horizontal movement with slight thrust components, similar to other segments of the East Kunlun fault zones. The results supports the “mainland escape” model.

Based on the statistics of cross-fault deformation anomalies before strong earthquakes during the last forty years, this article analyses the characteristics of the time duration, spatial distribution, amplitude of the anomalies and the relationship of all the three factors. it disgusses the anomaly characteristics of the measurement of cross-fault deformation as well as the maximum spacing of the cross-fault sites and observation cycle of the monitoring of different magnitude of earthquakes. The results suggest that: The anomalies are mainly of medium term as well as short and medium terms, occur more frequently one year before the earthquakes. The time duration of the anomalies is directly proportional to the earthquake magnitude. The spatial distribution of the anomalies also has a phenomenon that it extends as the augment of the epicenter distance. The amplitude of the anomalies enlarges with the increase of time duration and reaches to higher level when the epicenter distance is within 160 to 350 km. The anomaly shape is devided into two main types:trend and mutant. The spacing of monitoring cross-fault sites of different earthquake magnitude can be different: The spacings for monitoring magnitude 7 earthquakes should be less than 450 km, and 300 km, 200 km, 100 km for magnitude 6, 5, 4 earthquakes respectively. The measurement cycle is supposed to be within three months.

Hebei province is one of the most active areas of seismic activity in north and even east mainland China, there is complex tectonic background and fault development. Along with the development of the province’s 11 urban active fault detection and seismic risk evaluation project, some scientific projects and the accumulation of the fault structural study data, late Pleistocene fault data is further updated. Then, there is an important question of how to assess the maximum potential earthquake magnitude and the risk of these active faults on long-term earthquake prediction. Using the maximum potential earthquake magnitude assessment model proposed by Wen Xue-ze, we first divided fault cell to the active faults in Hebei region, then formed the empirical relationship between the maximum magnitudes M_max and the a_t/b values of the sub-areas' frequency-magnitude relationship in the Hebei area, and got the upper limit of the potential magnitude in fault cells by the formula. Furthermore, we calculated the seismogenic probability of partial fault area in the future strong earthquakes through the exponential relation with earthquake waiting time.

Features of seismic sequence can directly reflect the differences among tectonic stress field, seismotectonic and seismogenic environment. For example, mainshock-aftershock-type earthquakes mostly occur in a relatively uniform medium environment. However, foreshock-mainshock-aftershock-type earthquakes and swarms mainly occur in complex structure. On 17 June, 2019, the M6.0 an earthquake occurred in Changning County, Yibin City, Sichuan Province. Its aftershock totally distributed along a NW direction belt, bit in the northwest part of the belt, the aftershock distribution showed the cluster features. There is an obvious difference between the southeast part and northwestern part for aftershock activity. The southeast part can be considered as a mainshock-aftershock type with a fast decay. The northwestern part shows a feature of swarm, which decay is slowly and many aftershocks with M5 or more in the early stage. The M6.0 earthquake occurred in the Changning-Shuanghe anticline which is complicated and composed of several secondary fold structures and associated faults. The segmentation characteristics of the Changning M6.0 earthquake indicate that it is hardly to be produced by a single fault but a cascade fractures. Moreover, the aftershock focal depths in the northwestern part are more deeply, this means that the seismic activity in this area has been controlled by the Huaying Shan fault zone. Oppositely, the possible influence of the 2019 Changning M6.0 earthquake on Huaying Shan fault zone should be emphasized in the future.

By using the method of differential GPS, on the basis of observing the features of the terraces in Huangshui basin, we have surveyed the parameters of the terraces in Huangshui basin, and primarily ascertained the characteristics of neo-tectonics in this region, and also found out the distribution and movement features of the active faults around Xining City. Through the research described above, we draw a conclusion as follows: by using the DGPS, the coordinate and elevation of the terraces can be quickly and accurately acquired; so the DGPS is a feasible way to find the positions and other features of weak active or concealed faults. T₃, T₄, T₅ terraces is dislocated by Nan chuan river fault between 0.10 Ma B.P. and 0.05 Ma B.P. with the least velocity of 0.15 mm/a.

Machine learning (ML), especially deep learning (DL), has developed rapidly in recent years, which has made exciting progress in many applications such as data mining, computer vision, natural language processing, data feature extraction and prediction. Earthquake prediction is a complex, wide-ranging, immature, and controversial scientific issue. Its development is limited by unclear earthquake mechanisms and seismogenic structures, incomplete observation data, and unclear earthquake phenomena. However, machine learning may improve the mining and discovery of complex seismic data and promote the development of earthquake prediction science. This article reviews the application of machine learning in earthquake prediction, including the prediction of big earthquakes, big aftershocks and rock experimental fractures, finally looks forward to the research trends of machine learning in earthquake prediction.

Numerical simulation techniques and adjoint method lead to the successful application of adjoint tomography in both regional and global full waveform tomography. Based on the spectral element method, adjoint tomography adopts full three-dimensional model as initial model for waveform modelling and calculates gradients efficiently through interaction between forward wavefield and adjoint wavefield. Owing to the power of high-performance computing, adjoint tomography utilizes full-wave tomography at large scale. Compared with traditional tomography techniques, adjoint tomography can describe the subsurface anomalies more detailed and comprehensively, so it is more favorable in deep dynamics research. Here we firstly introduce the basic theory of adjoint tomography, its workflow of implementation, and then we give a review of its worldwide applications, while finally a brief prospect of future developments is discussed at the end of this article.

the principle and algorithm of neural networks of Radial Basis Function (R BF) and its application to the expert system for earthquake prediction (ESEP 3.0) are introduced in this paper. The actual application in earthquake forecast shows that the neutral networks can overcome some demerit of BP neural networks in leaning process, the constringency excessively depend on initial value and optimization constringency and often can′t appear. The RBF neural networks possess the rapid operation speed in learning and strong nonlinear mapping ability and very good efficiency.

The depth of Zhao Gezhuang well is 200 m. The observation aquifer is located in 182—200 m, which is a mixture of shallow cold water and deep hot water. Under the influence of mining and rainfall, the water level and water temperature have synchronous coordination changes in the long trend and annual variation. Due to groundwater exploitation, the ratio of cold water in the shaft reduces, the water level of the well decreases, and the water temperature raises. The rainfall infiltration recharge makes the cold water in wellbore increase, water level rise and water temperature drop. However, at the end of the rainy season, the inflow of cold water into the shaft decreases, and the water temperature rises gradually. The air pressure and the solid tide cause the diurnal variation of water movement between the wellbore and the aquifer, so that well water level has periodic fluctuation. This changes of the ratio of cold and hot water in the wellbore and causes the secondary effect of water temperature's periodic fluctuation. Both of them show synchronous and coordinated changes in diurnal variation. Different kind of interference factors causes different periodic change. It is necessary to choose different method and sampling period in order to eliminate the disturbance and extract the information of seismic anomaly.

Ambient noise tomography is a rapidly emerging field of seismological research. Applying ambient noise to earth structure research can avoid dependence of earthquake signals effectively, meanwhile, ambient noise method can obtain upper crust structure with higher resolution as well as the structure beneath urban area because ambient noise contains abundant short period information. This paper aims to analysis advantages and disadvantages using ambient noise tomography by showing its present state, process method and progress. Anisotropy inverted by a combination of ambient noise data, surface and body waves can accurately reveal crust-mantle structure and geodynamic characteristics of deep structure. Combining noise analysis and other active signal analysis techniques can further study variations of seismological parameter and physical properties before and after earthquake.

This paper proposed a new method for identification of ionospheric TEC anomalies using prophet forecasting model based on Facebook. First, we compared the precision of this new method with the traditional time series forecasting method (Autoregressive Integrated Moving Average, ARIMA models) and the identification method of the classical ionospheric TEC anomalies (Inter Quartile Range, IQR method), in predicting the background values of ionospheric TEC modeling. The results show that the precision of the former is obviously better than the latter two methods: about 2.55 times higher than that of the ARIMA models, and about 10.74 times higher than that of the IQR method. Meanwhile, when the best prediction modeling interval is established, the comparison of precision values is RMSE_IQR=10.5841>RMSE_ARIMA=3.2780>RMSE_Prophet=0.846, indicating that the traditional detection methods have insufficiency in predicting modeling background values. Second, taking the August 8, 2017 Jiuzhaigou earthquake as example, we analyzed its ionosphere TEC anomalies and proved the effectiveness and accuracy of the new method. The results show that obvious ionosphere TEC negative anomalies appeared on the 10th and 2nd days before the earthquake, and obvious ionosphere TEC positive anomalies occurred on the 7th day before the earthquake. In addition, the comparative experiments show that the validity and accuracy of the Prophet forecasting model is significantly better than the IQR method

In this paper, the important significance of the 2001 Kunlunshan large earthquake with M= 8. 1, theorderly characteristics of the time and space of strong earthquake activity from 1996 to 2001 in western China and the correlation of strong events between western part of China's mainl and and Taiwan have been discussed. The trend of M≥ 7 events in future in Northern part of Qinghai-Xizang block has beenestimated by using the method of orderliness analysis.

Daily variation ratio of geomagnetic vertical component (Z) is important in the study of earthquake precursor analysis. The variation magnetic field makes an induced magnetic field because of the earth conductivity, and the induced magnetic field includes information from outer magnetic field and underground electrical conductivity, so the geomagnetic field Z component reflects more changes of underground activity than other components. We collected data of Jiangsu area since 1984 and got 29 events of anomalies with day by day ratio, and then carried out a statistical analysis on the relation between them by combining geomagnetic storm and the earthquake after the abnormal events. The study has found that the anomaly event of day by day ratio and earthquake have a good correlation without geomagnetic storm, with coefficient of 0.77, while the corresponding relationship drops to 0.25 with geomagnetic storm. Combining all of the abnormal events, we consider that, after the abnormal event of day by day ratio, the possibility of the abnormal event of day by day ratio being an earthquake precursor will be 0.8 if there is no geomagnetic storm on that day or the Dst index is smaller than that on the second day. Otherwise, the abnormality maybe be caused by geomagnetic storm rather than the influence of underground activity.

This paper describes the development of water temperature research from three aspects—influence factors, response mechanism of water temperature to dynamic loading and hydro-thermodynamic theoretical model. High-precision digital observation technology provides reliable and effective data support for the scientific research of well water temperature. Source of replenishment and hydrodynamic action are two major factors that affect the dynamic change of well water temperature. The source of replenishment determines the shape of the vertical distribution curve of the temperature of the well and aquifer system. Hydrodynamic action determines the amount of groundwater recharge and the speed of groundwater flow in the aquifer, thus affecting the temperature change of the well-aquifer system. And the dynamic loading affects the flow speed of water within the well-aquifer system and changes the water temperature. Through the summary of the study on the factors influencing the water temperature of the well and the formation mechanism of water-thermal dynamics, it is helpful to clarify the relationship between the water temperature of the well and the aquifer, and provides an important research method for the quantitative analysis and mechanism interpretation of the water temperature of the well.

From the perspectives of energy of deep and shallow earthquakes and their energy release ratio as well as duration, the rhythm repetition of the end earthquakes of the fifth activity period and orderly activity image of moderate strong earthquake in the fifth activity period in northeastern China, we analyzed and compared characteristics with that of the former four periods. The results show that the energy release of the fifth activity period is far lower than other activity periods, energy release ratio of deep earthquakes and shallow earthquake is large, and the sustained time is long. The “closing door” earthquakes sustained the rhythm repetition of the former 4 activity periods. The properties of the “closing door” earthquakes include time and spatial clustering as well as earthquake swarm, seismic gap and banded orderly distribution image. The 7 earthauakes of M_S≥5.0 in 2013 may be the “end” earthquakes of the fifth activity period.

With the rapid development of China's national economic construction and the increasing complex of the power environment, power frequency interference effects on the geo-electric field are becoming more and more serious. Power frequency interferences produced by power supply system are a kind of electro-magnetic interference in the geo-electric field observation in China. We first briefly introduce the method of geo-electric field observation. Second, we analyze in detailed the principle, methods, effects and the mechanism of power frequency interferences in the geo-electric field observation. And then, we systematically investigate suppression method for power frequency interferences and its particularity in geo-electric field observation. Finally, the effects of power frequency interferences suppression is discussed, combined with the actual geo-electric field observation.

Since the concept of WebGIS appeared, its theory and application have been researched in our count ry.But it is still under the ex perimentation until now, so it cannot be called the real “WebGIS”.So it is necessary to summarize the research results for these years. This paper sums up the main characteristics of WebGIS on the basis of collecting and studying agreat deal of published scientific thesises, research report s, deg ree thesises and applications. The paper also sums up the key problems and realizing technology of WebGIS, and its application status in agriculture, forest ry, weather, water conservancy, earthquake, ocean, land and resource, environment protection, railroad and t raffic, electric pow er, city const ruction and prog ramming are emphasized.Finally the paper discusses the development t rend of WebGIS. The conclusion is that WebGIS can be used more w idely as an opening application plat form.

A quick assessment method of earthquake damage loss based on Remote Sensing (RS) is introduced in the paper, which includes two parts, damage information acquisition and loss assessing. Damage information acquisition contains earthquake damage index mode and image classification mode. The former obtains macro earthquake damage of resident sites on ground through the relationship between damage index and intensity, and the latter uses digital image processing technique to gain the classified earthquake damage. The loss assessment is different according to the different modes of damage information acquisition. This method based on RS and GIS satisfies the actual demand, establishing a multi-person working mode and increasing the speed of earthquake damage assessment based on RS.

The geoelectric field is an important part of the earth electro-magnetic field. Using the traditional time series statistical analysis method, this paper studies and discusses the variation characteristics of the second sampling data of the geoelectric field observed from Xiannushan seismic station, which belongs to the Chongqing municipality. The results show that: ① before and after Changning M_S6.0 earthquake, the anomalous change of the geoelectric field were recorded at Xiannushan seismic station, 390 km away from the epicenter; ② the average azimuth angle of the anomalous change was N77.55°E, approximately from the epicenter of Changning M_S6.0 earthquake to Xiannushan seismic station; ③ the typical anomalous change of the geoelectric field was intermittent and non-periodic disturbance, which densely appeared 8 days before the main shock of Changning M_S6.0 earthquake, lasted to the 4th day after the main shock, and then gradually transformed into the high-frequency disturbance changes; ④ the anomalous change of the geoelectric field appeared in lots of clusters, each of which is composed of multiple groups of step mutation with nonlinear attenuation. According to the comprehensive analysis, the anomalous change of the geoelectric field before and after Changning M_S6.0 earthquake, may be related to the filtered electromotive force generated by the high-pressure migration of the underground fluid, during the change of the structural fracture and the process of the rock micro fracture.

In this paper, focal mechanism solutions of 4303 earthquakes occurred in and around the mainland of China (15°~55°N, 65°~125°E) from 1976 to 2018 are collected, and the focal mechanism solutions and the spatial distribution characteristics of the P, T axis are analyzed. Using these focal mechanism solutions, we obtained a 2-D tectonic stress field distribution. The results of stress field inversion show that the strike-slip stress is dominant in most of Yunnan, most of the Tibet Plateau and most of North and South China. The strong collision between the Indian plate and the Eurasian plate controls the western part of China. A large number of fault-type earthquakes are concentrated in the Tibet Plateau and the Tianshan area of active block in the western region. There are also normal fault type earthquakes in the Tibet Plateau interior, and the direction of the stress field changes greatly at 26°N. In the Yunnan-Myanmar active block located south of the eastern tectonic line of the Tibet Plateau, the direction of the maximum principal compressive stress changes from the direction of NNE to the direction of NNW. From the northeast block to the North China block and the South China block, the maximum principal compressive stress direction has a rotational tendency from NE to EW and NW.

Detailed field investigation showed that three seismogenic faults ruptured in the Wenchuan M_S8.0 earthquake, which are Beichuan-Yinxiu fault, Penxian-Guanxian fault, and Xiaoyudong fault. The Beichuan-Yinxiu fault is characterized by reverse faulting in the south and right-lateral faulting in the north, which lasted for 220 km long and vertically displaced 3 meters on average, and can be divided into three segments. The Penxian-Guanxian fault rupture is characterized by reverse faulting which is 5.6 km long and vertically displaced 1.5 meters on average, and can be divided into two segments. Xiaoyudong secondary fault is characterized by tear faulting and was formed in this earthquake, left-laterally faulted 5.6 km long with 1.5 m vertical displacement on average, which accommodated the different deformations of tectonic units on both side. The surface rupture on Yaodu town may show the different characteristics between Nanba segment and Beichuan segment. The geometry and motion mode indicate that the maximum horizontal main stress in this region is in the direction of NWW.

Spending more than 20 days in the Wenchuan earthquake zone, I conducted a systematic field investigation into the macro-anomaly cases occurred at the earthquake region in particular in Wenchuan, Dujiangyan, Yingxiu, Beichuan, Shifang, Mianzhu, Hanwang, Mianyang, Chengdu and other counties. This article is a summary of copious examples and instances and a series of abnormal phenomena taken place in electromagnetic field, underground fluid, geographical appearances, meteorological conditions, …etc. which are considered to be earthquake warning signs and premonitions in the seismic area. Regarding the emergence of the forewarnings of the earthquake as surely appearing phenomena, this article expresses a personal point of view about the reasons of the fail to anticipating the earthquake and maintains that the close cooperation between the experts and the mass people is an indispensable means for earthquake forecasting. Then, I suggests, firstly, to mobilize the mass people into the earthquake forecasting work and, secondly, to develop the macro-watching system for the prediction of earthquake and, finally, to promote a large education for popularizing seismic knowledge.

Based on the seismic waveform data from 2005 to 2016 in the border area of Shanxi-Hebei-Shandong-Henan provinces recorded by Handan Seismic Network, apparent stress values of 302 small and moderate earthquakes (2.0≤M_L<4.3) were calculated using near-surface Brune model and genetic algorithm. The range of apparent stresses of Shanxi-Hebei-Shandong-Henan border area is 0.01—3.26 MPa, with an average of 0.535 MPa. The scaling relationship between source parameters is discussed. The spatial and temporal characteristics of stresses are analyzed. The results show that there are some obvious high values of apparent stress and stress anomalies in many areas at the border area of Shanxi, Hebei, Shandong and Henan Provinces. The earthquakes mostly occur in the area of high apparent stress anomaly and its vicinity, and high apparent stress anomalies occurred before the majority of earthquakes. The results indicate that the abnormal high apparent stress give some indication to the prediction of the epicenters of moderate to strong earthquakes, which can be used as the basis of earthquake risk judgment at the border area of Shanxi, Hebei, Shandong and Henan.

The Minshan block is located in the middle of South-North Seismic Structural Belt in China with complex regional geological structures, numerous active faults and frequent strong earthquakes. Maowen fault, Tazang fault, Minjiang fault and Huya fault are the main active faults in different directions constitute the boundary of the Minshan block. From 638 to 2017, 11 powerful earthquakes of magnitude 6 or above occurred in this region, and the 2017 Jiuzhaigou M_S7.0 earthquake is one of them. Based on the regional tectonic background, this paper summarizes the structural characteristics and seismicity characteristics of strong earthquakes occurring in Minshan block.and comprehensively analyses the seismogeological characteristics and seismic hazards in this area. It is concluded that: ① The spatial distribution of earthquakes is characterized by obvious zoning, the most destructive strong earthquake generating structures are the East-West boundary fault areas of Minshan block with strong activity, and the epicenter is located at the intersection or cutting position of two or more groups of active fault structures. ② the temporal distribution of earthquakes is characterized by migration and return and in-situ recurrence with the development of time. ③ The occurrence of destructive earthquakes along the East-West boundary of Minshan block has a certain time correlation. The seismic sequence of Huya fault in the east boundary from 1973 to 2017 is the seismic structural response of Minjiang fault in the west boundary from 1933 to 1960 about 40 years later. ④ Minshan block should be the potential danger area of strong earthquake in the future, and the potential dangerous area of strong earthquakes in the north-central section of Minjiang fault is the area worthy of further study in the near future.

Quartz horizontal-pendulum tiltmeter has been widely used in seismic precursory observation. However, it still has some problems, for example, the sensitivity is unknown before on-site installation. To solve this problem, we introduce electrostatic force feedback technique into the quartz horizontal pendulum tiltmeter. We derive the theoretical transfer function and sensitivity of the instrument, and propose a method to realize both micro displacement measurement and electrostatic force feedback through a set of parallel metal plate structures. Then we perform detailed design and test. The experimental result shows that the accuracy of sensitivity parameter can be guaranteed after using the electrostatic force feedback technique.

On the base of data collection and on-the-spot investigation,this paper studies some characteristics of the Hujiaping M_S4.1 earthquake on 22 November, 2008 in Guizhou township, Zigui county, Hubei province, and the geology-hydrogeology condition and earthquake active background in the area. The earthquake disaster are investigated and analysed. Some scientific problems on earthquake precursors and causes of the earthquake are discussed. In our opinion, the Hujiaping M_S4.1 earthquake is a reservoir-induced earthquake belonging to tectonic type,induced by reservoir water-loading and water infiltration along the Xiannvshan fault,and there are some indications that the cause of earthquake possibly relates to the 2008 Wenchuan earthquake influence on the stress field of this region.

In order to study the geochemical characteristics of soil gas and the tectono-geochemical background reflected by fault gas in the Tong-Dong fault zone, the field monitoring method was used to analyze the concentration distribution of soil H₂ and Rn in the two observation lines of Zhanghe village and Xinglizhuang village. The results show that the distributions of H₂ and Rn concentration in Zhanghe village ranged from 0.24 to 174.7×10^-6 and 13.3 to 69.8 kBq·m^-3, respectively. The background values of H₂ and Rn concentration are 14.26×10^-6 and 24.8 kBq·m^-3, respectively. The range of concentration distribution of H₂ and Rn in Xinglizhuang observation line ranged from 11.8 to 67.06×10^-6 and 43.6 to 72.6 kBq·m^-3 respectively, with background values of 37.13×10^-6 and 72.6 kBq·m^-3, respectively. In the measure line of Zhanghe village, strong anomaly of H₂ and Rn appeared at 90～105 m, but a higher anomaly occurred at 120～150 m, with anomalous values near the fault zone, which indicates the location of the fracture effectively. Integrated geological structure and physical geography, it is concluded that the high value anomaly of the gas composition in the survey line are mainly controlled by the tectonic conditions, and it is also affected by sediment properties and meteorological factors. Therefore, we should further track and monitor the gas composition in the soil layer of the target fault zone, and analyze the temporal and spatial variation of fault activity, and take gas isotope techniques to explore the source of the components, so as to enhance the important role of gas geochemical indicators for fault tectonics activity and to strengthen the efficiency of earthquake prevention.

Multiply scattered waves are sensitive to media changes owing to the effect of re-peated sampling, superposition and amplification. Based on this characteristic, small medi-um changes could be detected by using coda wave interferometry. In recent years, coda wave interferometry is widely used in estimating velocity variation with high precision in areas such as seismology and non-destructive testing. This paper systematically presents the principle, method and research status of coda wave interferometry respectively, especially focusing on research advances of media velocity variations by using repeating earth-quake,artificial source, and ambient seismic noise. Applications of coda wave interferome try can contribute to the more subtle understanding of dynamic evolution process in the medium.

Based on the earthquakes recorded in Yibin area (28.0°N~28.5°N, 104.6°E~105.1°E), Sichuan Province, from January 2014 to August 2019, we estimated the b values in the studied area by the maximum likelihood method and obtained their temporal and spatial characteristics. The results show that, firstly, the b value decreased rapidly five months before the Changning M_S6.0 earthquake and recovered quickly after that. This phenomenon is likely to reflect the process of stress accumulation during earthquake preparation and stress release after the earthquake. Secondly, before the Changning earthquake, there was always a low b value anomaly (≤0.85) in the epicenter and its vicinity. Five months before the earthquake, a further decrease of b value occurred near the epicenter, especially in the northwest of Changning, where following three M_S5 earthquakes taking place in Gongxian were just located in this abnormal region and its edge area. Thirdly, the spatial distribution of low b value anomalies indicates the risk area of medium and strong earthquakes in the future. And, the fast decrease region in b value can be used to determine the possible location of strong aftershocks. Fourthly, when analyzing the seismic risk, we should pay more attention to the b value decrease under the background of long-term low b value, which illustrates the increasing seismic risk in high stress concentration area.

The Tazang fault is located in the eastern part of the East Kunlun fault zone with a length of 170 km, which constitutes the northeast border of Bayan Har block with Minshan fault zone. Satellite image and geological survey have revealed evidence for Holocene movement along the fault. The fault can be divided into three sections by the segmental signs of strike-slip fault, such as geometric and tectonic discontinuities in combination of geomorphic features and fault zone materials. The Locha section generally strikes NWW, developed sinistral left-step with Maqu fault in the west, and rotates clockwise on the Xiahuangzhai village in the east. The Dongbei village section generally strikes NW, and rotates anticlockwise on the entrance of Jiuzhaijou in the east. We divided the Dongbei village section into two sub-sections, and the northern and southern sub-sections are separated by the Minjiang fault. The Majiamo section is divided into three sub-sections, namely Zharu, Tangzhai, Wujiao sections. The elapsed time in Loucha and Majiamo sections was relatively short. The linear horizontal slip of the east Kunlun fault zone transforms into the vertical movement of the Minjiang fault zone and Huya fault zone which trends nearly SN~NNE, and the uplift of Minshan. The fault sections splay out from NW to SE that has good correlation with the slip gradients along the east Kunlun fault.

Self-noise level is one of the most important parameters of seismometers. So, how to lower down the self-noise level is a big issue in the design of seismometers. This paper introduces how the two major noise sources-Brownian noise and electronic noise (1/f noise)affect seismometer's self-noise level and transfer function. We analyzed base noise of seismic station recorded by three different kinds of seismometers and study how the self-noise affects the data recorded.

From the study of seismicity in Chinese mainland, we found that obvious low seismicity anomalies occur 1~2 years before some strong earthquakes. Using M≥5.0 seismic data in recent 100 years, in this paper the relations between low seismicity anomaly and future seismicity of Chinese mainland were analyzed. We established low seismicity indicator from annual frequency of M≥5.0 earthquakes, the maximum earthquake magnitude, and M≥6.0 seismic quiescence. Furthermore, the relations between low seismicity anomaly and future strong earthquakes were checked through probabilistic gain index β, predicting efficiency ratio α and R value for earthquake forecasting efficiency testing. Preliminary results indicate that some coefficients exist between low seismicity anomaly and future seismicity in Chinese mainland, mainly reflected in M≥7.8 huge earthquakes. However, the coefficients of M≥7.8 huge earthquakes are limited, and probabilistic gain index β and predicting efficiency ratio α are about 3, R value for earthquake forecasting efficiency testing is about 0.2. For M＜7.5 earthquakes, low seismicity anomaly is not exhibited, its probabilistic gain index β and predicting efficiency ratio α are near 0, which appear as random relations. The turning point at which some relations with low seismicity anomaly show is M7.5.

Studying the mechanical characteristics of the lithosphere in the areas where strong earthquakes have often happened are of significance for exploring the occurrence mechanisms of strong earthquakes. The lithosphere effective elastic thickness (T_e) and initial loading ratio (F) are closely related to the mechanical characteristics of the continental lithosphere. We use a new joint inversion method integrated both admittance and coherence techniques to compute the effective elastic thickness and initial loading ratio in the Chinese mainland, with the WGM2012 gravity data, ETOPO1 topographic data, and the data of Moho depth and crustal density from CRUST1.0 model. Based on the estimated T_e and F, we discuss that how the parameters of T_e, F, and gradients of them affect the environment for the development of strong earthquake. We find the high-degree earthquake tectonic areas tend to low T_e and high gradients of T_e and F. These suggest that the regions with a relatively low lithosphere strength, and those at the belts with sharp changes of lithosphere strength and internal load can provide a positive environment for developing strong earthquakes.

Hydrogeochemical anomalies of mud volcanoes and springs in the North Tians-han were found before and after the June 30,2012 Xinyuan-Hejing M_s6.6 earthquake in Xinjiang Uyger autonomous region, China. Water samples from the hot springs and mud volcanoes were collected 4-days before and after the earthquake, and hydrogeochemical par rameters were measured. The data indicate that water from mud volcanoes are brine with weak alkaline and low temperatures, whose chemical type is CI-Na and may originate from the meteoric water stored in the closed structures and react with the surrounding rock complex. Water from springs is fresh with weak alkaline and medium temperatures, whose chemical type is SO4·Cl-Na, probably owing to the deep circulation of the ground-water along the faults. The Anjihai mud volcano showed coseismic anomaly, with temper ature (T), total dissolved solids (TDS),K⁺,Na⁺ and Ca²⁺ increasing greatly after the . earthquake. Mud volcanoes in Dushanzi, Baiyanggou and Aiqigou showed pre-seismic a-nomaly, with the T, TDS, conductivity(EC),Na⁺ and CI^-increasing, and K⁺,Ca²⁺ and Mg²⁺ decreasing before the earthquake in Dushanzi and Baiyanggou mud volcanoes. In Aiqigou mud volcano, there were significantly decreases in K⁺ and Mg²⁺,but Ca²⁺ in-creased by 223%. For the Shawan No. 25 spring, there were significantly decreases in TDS, EC, K⁺,Na⁺,Ca²⁺,Mg²⁺, CI^-and $SO_{4}^{2-}$ but the temperature decreased by 7℃. These results may help earthqua ke tendency analysis and improvement of hydrogeochemi-cal monitoring methods.

The focal mechanisms of moderate-small earthquakes are calculated tentatively using digital seismic wave data in some provincial digital seismic networks based on the program of focal mechanism determinations combing the first motion of P, SV and SH waves with their amplitude ratio, which is recently developed by Snoke. Some results are compared with the results obtained by P first motion data. It shows that the method is feasible, and it provides a new possibility using digital seismic data in earthquake prediction.

As an integral part of seismological research, focal mechanism plays an important role in not only interpreting earthquake preparation, but also describing the nature of seismic source and rupture process to some extent. Rapid and automatic inversion system can speed up inversion and provides more source information, which potentially increases the efficiency of rescue operations, seismic regime analysis and aftershock prediction. In this paper, we elaborate on the inversion method for focal mechanism, and also summarize the construction ideas and the current research progress of automatic inversion system. Meanwhile, such system can provide technical ideas for the construction of automatic inversion system.