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| 1 | Study on the Criterion of the Correlation between Deformation Precursors and Earthquakes显示文摘The relationship between pre-seismic anomalous changes and earthquakes is one of the most basic information to comprehend the process of earthquake preparation and conduct earthquake prediction research.However,few researchers have carried out relevant investigations for a long time.In this paper,the distribution characteristics of deformation anomalies before the Wenchuan earthquake are analyzed,and the widespread distribution area is discussed.Based on previous studies,we improve the relationship between anomaly duration t and magnitude M by introducing distance D.The new model is characterized by lower magnitude fitting error,making it possible to establish the correlation between deformation precursors and earthquakes.The correlation standard between precursors and earthquakes here is defined as Niu's criterion,which is applied to analyze and interpret the relationship between the shortterm anomalies of Hongliuxia fault leveling and the Wenchuan and Jiuzhaigou earthquakes. | NIU Anfu ZHAO Jing YAN Wei ZHANG Jing ZHANG Lingkong YUAN Zhengyi YUE Chong | 2020 | Earthquake Research in China2020，34，3： | 1 |
| 2 | The method of AF synthetic detection on crust deformation anomaly and its application in earthquake prediction 显示文摘 | Niu Anfu Li Xudong and Wu Jing | 1998 | Acta Seismologica Sinica1998，11，3： | 1 |
| 3 | Correlation between the tilt anomaly on the vertical pendulum at the Songpan station and the 2021 MS7.4 Maduo earthquake in Qinghai province,China显示文摘Understanding the relationship between precursory deformation anomalies and strong earthquakes is vital for physical earthquake prediction. Six months before the 2021 MS7.4 Maduo earthquake in Qinghai province, China, the vertical pendulum at the Songpan station was observed to tilt southward with a high rate and large amplitude. Studies conducted before the 2021 MS7.4 Maduo earthquake inferred the tilt anomaly to be an earthquake precursor. However, after the earthquake, the relation between the earthquake and the anomaly became controversial, partly because the Songpan station is located at a great distance from the epicenter. In this study, based on the deformation anomaly characteristics, relationship between the seismogenic fault and the fault near the anomaly, and associated quantitative analyses, we concluded that this anomaly may be associated with the 2021 MS7.4 Maduo earthquake. The duration and amplitude of this anomaly matched with the magnitude and epicenter distance of the Maduo earthquake. We have also interpreted the reason why the anomaly occurred near a fault that is obliquely intersected with the seismogenic fault and why the anomaly is located far from the earthquake epicenter. | Anfu Niu Zhengyi Yuan Jin Wei Jing Zhao Wei Yan | 2022 | Earthquake Science2022，35，3： | 1 |
| 4 | Calculation of Ground Vertical Displacements,Tilts and Their Distribution Characteristics around an Irregular Load显示文摘Based on the load model of a uniform isotropic semi-infinite elastic medium,we deduced a calculation of vertical displacement and tilt and proposed a method of calculation of vertical displacements and tilts caused by irregular load on the ground or underground at a certain point with two-dimensional and three-dimensional shapes. We compared the difference between the simplified model and the irregular model. Finally,the vertical displacements near the irregular load and the distribution of horizontal tilt are presented.The results show that,compared with the point simplified model,the irregular load model has certain advantages for describing the near field. The establishment of a twodimensional irregular load model can help with the calculation of the modal vector superposition after load scattering. The three-dimensional irregular load model can redistribute load through different weights given to the scattered points after the load scattering,and then obtain displacement with the vector calculation method. The results of vector superposition calculation from the scattered irregular load both in two-dimensions and three-dimensions are all convergent obviously as grids become denser,and it is shown that the calculation method is correct and feasible. | Yah Wei Liang Libo Niu Anfu Chen Guoqin | 2016 | Earthquake Research in China2016，30，2： | 0 |
| 5 | Slip Rates of the Major Faults on the Mid-southern Section of the North-South Seismic Belt Calculated from the Block Theory显示文摘In this paper,using the 1999 ~ 2007 GPS velocity field data,and by choosing the optimal block model,we obtained the deformation models applicable to the boundary zones of major blocks and the slip rates of block boundary faults on the mid-southern segment of the North-South Seismic Belt. The results show that: on the Longmenshan fault zone,the tensional and compressive slip rate is small on the Baoxing-Wenchuan segment,about 0. 5 ~ 1. 8mm·a- 1, and the rate is relatively significant on the segment of the Wenchuan-Maoxian,as 1. 8 ~ 3. 8mm·a- 1; on the Xianshuihe fault belt,there is a certain difference in spatial distribution between the tensional slip rate and strike-slip rate: the tensional slip rate( 8. 1mm·a- 1) is bigger than the sinistral strike-slip rate( 4. 8mm·a- 1) at the north of the Luhuo region; the tension and compression slip rate is basically the same as the strike-slip rate at Luhuo-Dawu; the Dawu-Kangding section presents a trend of decreased strike-slip rate and increased tensional slip rate; the Kangding-Shimian segment shows a strike-slip nature; the strike-slip rate is significantly greater than the tension /compression rate on the Xiaojiang fault zone; the slip rate on the Red River fault zone shows obvious spatial segmentation,the slip rate is smaller in its northwest part,but with a certain amount of tensional /compression component,4. 7mm·a- 1on the Jingdong segment. The segment east of Jingdong( western Gejiu) is mainly of strike-slip,with a slip rate of 4. 5mm·a- 1. | Yan Wei Wu Yanqiang Niu Anfu Li Xiaofan Zhang Lingkong Ji Ping | 2014 | Earthquake Research in China2014，28，1： | 0 |
| 6 | A STUDY ON RELATION BETWEEN CONTINUOUS RAPID DEFORMATION AND EARTHQUAKLES显示文摘Continuous Rapid Deformation (CRD) may be an important precursor before some strong earthquakes with magnitude greater than \%M\%s5.0. This paper shows some characteristics of CRD, and proposes a method for identifying precursory CRD that is closely related to the process of earthquake preparation. From the deformation data in Yunnan Sichan provinces, we obtained the tilt and strain thresholds of 4.5ms/d and 5 ×10 -7 /d, respectively. Compared the tilt CRD in this region before 9 earthquakes (short term fore shocks and after shocks not included) with magnitude greater than 5.8 in the period from January of 1990 to May of 2001, we found that 8 earthquakes occurred within 5 months after the CRD with a duration of more than 20 days and a tilt velocity of more than 4.5ms/d without false prediction, but with one failure in earthquake prediction. For the strain CRD, 5 earthquakes occurred after the CRD; there was no false prediction, but 4 earthquakes unpredicted. We have tried to increase the thresholds, but found either the failure ratio or the rate of false prediction increased, while the success rate not obvious increased. | Niu Anfu, Zhang Jing, Gao Fuwang, Ji Ping and Yan Xudong (Center for Analysis and Prediction, CEA, Beijing 100036, China) | 2003 | 大地测量与地球动力学2003，23，B12： | 0 |
| 7 | Analysis of Dynamic Variations of Crustal Density in the Longmenshan Area before the Wenchuan M_S8.0 Earthquake显示文摘Based on the repeated gravity observation data from 1996 to 2007 from the Longmenshan gravity network,which has been dealt with by adjustment processing,the benchmark interference removal and impact of elevation changes removal,and by using the 3-D inversion method to reflect underground density, we analyze the characteristics of Longmenshan regional dynamic crustal density at depths of 25 km,20km and 15 km. The results show that in the Wenchuan earthquake preparation process,the regional density field showed marked characteristics both in time and space distribution. From the point of time process,the density change trend in the ten years before the earthquake presents a periodic change pattern: steady phase,dramatic stage,slow reducing phase and slow increase phase. The degree of density changes is from large to small,which means that earthquake gestation has reached the final stage. From the point of space distribution,density change distribution has a tendency of 'dispersion—relative concentration ',this shows that before the earthquake, the entropy of the underground density field was decreased. In addition,dramatic density changes often occur in the Longmenshan fault zone and western Sichuan plateau. Also,with the increase of depth,the trend of density change is more and more obvious. Through comparative analysis,the influence of density change on gravity is much bigger than that from height change. | Li Yuan Niu Anfu Liu Xikang Zhao Jing | 2015 | Earthquake Research in China2015，29，3： | 0 |
| 8 | On the Occurrence Time of an Earthquake Cluster in the Shanxi Reservoir显示文摘An earthquake cluster occurred in the Shanxi reservoir, located around Wenzhou city in Zhejiang Province. From February 4 to February 11, 2006, 9 earthquakes with M_L≥4.0 occurred, and the greatest magnitude was M_L4.6. The correlations of earthquake occurrence time with reservoir level changes and tides are discussed, and the possible factors that induced the reservoir earthquakes and the trend of seismic activity are analyzed based on the characteristics of earthquake occurrence time. Finally, we suggest that it is necessary to slow down the speed of storing water and to maintain a level below the highest historical level to avoid greater earthquakes in the reservoir. | Niu Anfu Zhang Xiaodong Zheng Dalin Li Xiaofan Ji Ping | 2006 | Earthquake Research in China2006，20，4： | 0 |
| 9 | Propagation of crust deformation anomalies related to the Menyuan M_(S) 6.9 earthquake显示文摘Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research. In this paper, the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method. By analyzing the characteristics of these anomalies, we found that: 1) The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau, where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2) The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation, and the migration rate is about 2.4 km/d. The propagation pattern is counterclockwise, consistent with the migration direction of M_(S)≥ 6.0 earthquakes;3) The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥ 6.0. Finally,based on the results of gravity field variation and the theory of crust stress wave, the law of deformation anomaly distribution was discussed. We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow. | Anfu Niu Chong Yue Zhengyi Yuan Jing Zhao Wei Yan Yuan Li | 2023 | Earthquake Research Advances2023，3，4： | 0 |
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