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Electromagnetic Anomalies around The Wenchuan Earthquake and Their Relationship with Earthquake Preparation  [PDF]
Xuemin Zhang,Xuhui Shen
International Journal of Geophysics , 2011, DOI: 10.1155/2011/904132
Abstract: Electromagnetic precursors before the Wenchuan earthquake on May 12, 2008 were collected and summarized on the basis of related published papers. The relationship between electromagnetic anomalies and different earthquake preparation stages was analyzed, and an entire seismic preparation process was constructed according to corresponding anomalies in different electromagnetic parameters. It is illustrated that stereo electromagnetic observation is useful in the understanding of earthquake preparation mechanism. It is inevitable that a lot of problems exist in anomaly distinguishing and coupling mechanism analysis, which needs further studies in future. 1. Introduction The ground-based electromagnetic precursor observation has been developed in China for more than 40 years, which includes the observation of resistivity, electric field, geomagnetic field, electromagnetic emissions, and so on. When the Wenchuan earthquake took place on May 12, 2008, lots of electromagnetic stations were observing in normal operation condition. Until now, many papers have been published about this destructive event, in which many anomalies were found not only in ground-based information but also in space ionospheric detection (e.g., [1–4]). All these electromagnetic phenomena illustrated their relationship with this strong earthquake. It is regretful that most anomalies were obtained and published after the earthquake, so they did not play a great part in earthquake prediction. The main purpose of this paper is to summarize the electromagnetic anomalies and think about what we can learn from them. 2. Electromagnetic Anomalies around the Wenchuan M8.0 Earthquake 2.1. Ground-Based Observation and Anomalies 2.1.1. Resistivity Observation Taking into account the big magnitude of the Wenchuan earthquake, 8 stations were selected in the distance of 500?km, in which the Pixian station is the nearest one, 36?km to the epicenter (e.g., [2]). Figure 1 shows the time series in resistivity at three stations during 2003–2008, in which 1(a), and 1(b) show curves at two perpendicular directions, NE (North-East) and NW (North-West) at the Pixian station, 1(c), 1(d) at EW (East-West) and NW direction (330?km to the epicenter) at the Ganzi station and 1(e), 1(f) at NW and NS (North-South) (290?km) at the Wudu station. Obvious anomalies were observed at these 3 stations, with the resistivity decreasing since 2006 relative to the normal level during 2003–2005, being about ?7.2% at NE direction at the Pixian station, ?4.5% at EW direction and ?3.3% at NW direction at the Ganzi station, +2.5% at
Study of the ionospheric anomaly before the Wenchuan earthquake
Tao Yu,Tian Mao,YunGang Wang,JingSong Wang
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-008-0587-8
Abstract: The behavior of the ionosphere before the Wenchuan earthquake is analyzed with the global TEC and ionospheric foF2 observed at Xiamen. It can be found from TEC maps that in the afternoon (16–18LT) on May 9, 2008, 3 days before the earthquake, there is an enhancement of TEC with an amplitude of 10–15 TECU appearing in the east-south direction of Wenchuan, and another enhancement appears at the conjugate region of the Southern Hemisphere with an amplitude of 10 TECU, but no obvious increment or decrement can be seen in other regions on global scale. It can also be found that on May 6 (6 days before the great earthquake), there is a decrement of TEC with small amplitude of 4TECU and larger area with 80° along the longitude in southern China, and there is no synchronous decrement observed at the conjugate region of the Southern Hemisphere. There are also many anomalies observed by ionosondes across China. The result shows that foF2 and TEC abnormally increased, which is different from pervious results that ionospheric parameters decreased prior to earthquakes. Preliminary results suggest that the enhancement on May 9 maybe has a close relationship with the possible enhancement of ionospheric electric fields, and it may be an ionospheric precursor of earthquakes. Whereas the decrement on May 6 may be attributed to the geomagnetic disturbance appearing on May 5.
Stress rise precursor to earthquakes in the Tibetan Plateau  [PDF]
Zhenhan Wu, Qunce Chen, Patrick J. Barosh, Hua Peng, Daogong Hu
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.58A1006
Abstract:

Earthquake prediction thus far has proven to be a very difficult task, but changes in situ stress appear to offer a viable approach for forecasting large earthquakes in Tibet and perhaps other continental regions. High stress anomalies formed along active faults before large earthquakes and disappeared soon after the earthquakes occurred in the Tibetan Plateau. Principle stress increased up to ~2 - 5 times higher than background stress to form high stress anomalies along causative faults before the Ms 8.1 West Kunlun Pass earthquake in November 2001, Ms 8.0 Wenchuan earthquake in May 2008, Ms 6.6 Nimu earthquake in October 2009, Ms 7.1 Yushu earthquake in April 2010 and the Ms 7.0 Lushan earthquake in April 2013. Stress near the epicenters rapidly increased 0.10 - 0.12 MPa over 45 days, ~8 months before the Ms 6.6 Nimu earthquake occurred. The high principle stress anomalies decreased quickly to the normal stress state in ~8 - 12 months after the Ms 8.1 West Kunlun Pass and the Ms 8.0 Wenchuan earthquakes. These high stress anomalies and their demise appear directly related to the immediate stress rise along a fault prior to the earthquakes and the release during the event. Thus, the stress rise appears to be a viable precursor in prediction of large continental earthquakes as in the Tibetan Plateau.

Electromagnetic Anomalies around The Wenchuan Earthquake and Their Relationship with Earthquake Preparation  [PDF]
Xuemin Zhang,Xuhui Shen
International Journal of Geophysics , 2011, DOI: 10.1155/2011/904132
Abstract: Electromagnetic precursors before the Wenchuan earthquake on May 12, 2008 were collected and summarized on the basis of related published papers. The relationship between electromagnetic anomalies and different earthquake preparation stages was analyzed, and an entire seismic preparation process was constructed according to corresponding anomalies in different electromagnetic parameters. It is illustrated that stereo electromagnetic observation is useful in the understanding of earthquake preparation mechanism. It is inevitable that a lot of problems exist in anomaly distinguishing and coupling mechanism analysis, which needs further studies in future.
泸州井地下水位中期异常特征和试用性预测指标的初步研究
A Preliminary Study on the Medium Term Anomalies of Groundwater Level of Luzhou Well and the Tentative Index for Earthquake Prediction
 [PDF]

李雅蓉,杨贤和
- , 2015, DOI: 10.3969/j.issn.1000-0844.2015.增刊2.0170
Abstract: 利用定性与定量相结合的方法,系统分析1982-2014年泸州井水位的月均值观测资料。发现有6次中期异常变化,分别对应1989年巴塘东南6.6级、2008年汶川8.0级等5次强(大)震,其中汶川8.0级地震出现了两次异常;并与川滇地区其他井(泉)对比,证明泸州井水位的中期异常明显,且不是孤立存在的;探讨了该井在汶川地震前后异常表现的特殊性,即出现"二次异常",震后效应亦显著和持久。最后提出利用泸州井水位从属函数异常计算发震时间的中期预测试用性指标,该指标可计算川滇地区最有可能发生强震的时间段。
The seismic behavior monitoring of groundwater in China has over 40 years history. Cooperated with other precursor means, it has become one important means of all means for earthquake prediction. But the earthquake-reflecting condition of each well and the evaluation of them is different. People have different views on the revocation of Luzhou well in recent years. This paper selects historical target earthquakes based on the earthquake cycle and magnitude in Sichuan and Yunnnan area. We use the method combining qualitative(monthly average method) and quantitative(23 points smoothing method and subordinate function method) approaches to make a systematic analysis on monthly observation data of Luzhou well groundwater level from 1982 to 2014. We found 6 middle-term anomalistic changes, respectively, corresponding to one MS6.6 earthquake occurred at Batang in 1989 and five strong earthquakes including Wenchuan MS8.0 earthquake. Among these 6 middle-term anomalies, 2 anomalies belong in the Wenchuan MS8.0 earthquake. Also, these anomalies were tested by R value. Compared with other wells in Sichuan and Yunnan Province, facts have proved that the middle-term anomalies of Luzhou well water level are obvious, and are not unique case. In addition, the particularity of anomaly before the Wenchuan earthquake and post the Wenchuan earthquake is discussed. That is, second anomaly, and post the Wenchuan earthquake effect is remarkable and lasting. We use the statistical data and the subordinate function of the water level of Luzhou well to calculate the tentative index for middle-term prediction on the occurrence of earthquake. The index can be used to predict the period when a strong earthquake can most likely occur in Sichuan and Yunnan area. Finally, we come up a conclusion that Luzhou well can be used to perform a study on middle-term anomaly and prediction on strong earthquakes while there need to strengthen the management and study of the well. Also, we suggest waterfall can be used as a observed item since waterfall is relevant to the groundwater.
Study of the ionospheric anomaly before the Wenchuan earthquake

Tao Yu,Tian Mao,YunGang Wang,JingSong Wang,

科学通报(英文版) , 2009,
Abstract: The behavior of the ionosphere before the Wenchuan earthquake is analyzed with the global TEC and ionospheric foF2 observed at Xiamen. It can be found from TEC maps that in the afternoon (16–18LT) on May 9, 2008, 3 days before the earthquake, there is an enhancement of TEC with an amplitude of 10–15 TECU appearing in the east-south direction of Wenchuan, and another enhancement appears at the conjugate region of the Southern Hemisphere with an amplitude of 10 TECU, but no obvious increment or decrement can be seen in other regions on global scale. It can also be found that on May 6 (6 days before the great earthquake), there is a decrement of TEC with small amplitude of 4TECU and larger area with 80° along the longitude in southern China, and there is no synchronous decrement observed at the conjugate region of the Southern Hemisphere. There are also many anomalies observed by ionosondes across China. The result shows that foF2 and TEC abnormally increased, which is different from pervious results that ionospheric parameters decreased prior to earthquakes. Preliminary results suggest that the enhancement on May 9 maybe has a close relationship with the possible enhancement of ionospheric electric fields, and it may be an ionospheric precursor of earthquakes. Whereas the decrement on May 6 may be attributed to the geomagnetic disturbance appearing on May 5. Supported by National Natural Science Foundation of China (Grant No. 40504023) and National High-Tech Research Program of China (Grant No. 500009003)
ANALYSIS OF CHARACTERISTICS OF PRECURSOR WAVE OF LOW FREQUENT IN SHANXI BEFORE WENCHUAN Ms8.0 EARTHQUAKE
汶川Ms8.0地震前山西前兆低频前驱波特征分析

Zhang Shuliang,Liu Ruichun,Ning Yaling,Tang Leili,Li Bin,
张淑亮
,刘瑞春,宁亚灵,唐垒黎,李斌

大地测量与地球动力学 , 2009,
Abstract: The changes of some precursory observation in Shanxi area before Wenchuan Ms8.0 earthquake on May 12,2008 were analysed,and following conclutions are drawn.Firstly,the precursor waves of low frequent are main characters of the precursory change before the earthquake,and its superior period are 64-128 min.Secondly,the distribution of the abnormal points is in the same direction with the primary rupture of Wenchuan Ms8.0 earthquake.Thirdly,low-frequency precursory waves occured in a crowded time,mainly from 1...
ANOMALIES OBSERVED BY ULTRA BROADBAND SEISMOMETER BEFORE WENCHUAN EARTHQUAKE
超宽频带地震计观测到的汶川地震震前异常

Zhang Yan,Wu Yun,Lü Yongqing,Hu Jin,Lü Pinji,
张燕
,吴云,吕永清,胡静,吕品姬

大地测量与地球动力学 , 2011,
Abstract: According to the observations of 16 ultra-broadband seismometers from 1st to 12th May 2008,it is demonstrated that there were obvious anomalies in 64-512 s ahead of the Wenchuan Ms8.0 earthquake in some frequency exclusively from the impact of the typhoon,this phenomena might be information related to the earthquake preparation.
Wenchuan earthquake: Brightness temperature changes from satellite infrared information
YuanSheng Zhang,Xiao Guo,MeiJiao Zhong,WenRong Shen,Wen Li,Bin He
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-010-3016-8
Abstract: By using an alternative processing method for satellite infrared remote sensing data and adopting the China Geostationary Meteorological Satellite (FY-2C) infrared remote sensing brightness temperature data, we studied the great 2008 Wenchuan Ms8.0 earthquake. Results indicate the obvious characteristic period and amplitude, and distribution of thermal infrared anomalies before the Wenchuan earthquake. And we discussed the mechanism of the observed pre-earthquake thermal anomalies. The characteristics of observed thermal infrared anomalies are easy to be recognized and applied, and could provide a criterion for thermal anomalies of earthquakes.
The short-term anomalies detected by broadband seismographs before the May 12 Wenchuan earthquake, Sichuan, China
汶川大地震宽带地震仪短临异常及成因初探

HU Xiao-Gang,HAO Xiao-Guang,
胡小刚

地球物理学报 , 2008,
Abstract: We investigated broadband seismographic waveform data in 7~13 May 2008 from 40 seismic stations of the National Digital Seismograph Network of China(NDSN) after the 12 May 2008 Wenchuan earthquake,showing that obvious precursor was widely detected throughout China.The premonitory phenomena is that tremor amplitudes in the period band of 2~10 s have increased steadily within 1~3 days before the main shock rupture.Anomaly tremors can also be detected by gravimeters and tiltmeters.Tremor signals are widely detected in mainland China,but they are very strong in Southeastern China and weak in Western China.The possible slow slip of South China block before the great Wenchuan earthquake may be the cause of tremors,which is related to some frictional processes of the slow slip.
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