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A Study on the Seismic Velocity Changes before and after the 2016 M_S6.4 Menyuan Earthquake Using the Active Source Data in the Qilian Mountain

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Earthquake Research in China 2018年第4期32卷 549-559页

作者： Zou Rui Guo Xiao Zhang Yuansheng Qin Manzhong Yan Wenhua Lanzhou Institute of seismology China Earthquake Administration

The Qilian Mountain active source network data was processed using the methods of stacking, cross-correlation and interpolation, and the airgun travel time variation characteristics of P and S waves around the January 21,2016 MS6. 4 Menyua,Qinghai earthquake. The results show that about 6 months before the earthquake,the relative travel time of three stations near the epicenter showed a declined change( travel time decrease),and such a change of low value anomaly was recovered about 3 months before the earthquake. The travel time decrease then appeared again, and the earthquake occurred during the recovery process. The maximum decrease of the S-wave travel time was 18 ms,and the change in travel time returned to normal after the earthquake. The variation trend of the 3 stations is consistent,including the S-wave travel time change of station ZDY38,which is nearest to the epicenter and changed obviously,and the variation range of the travel time is smaller at the stations afar. This variation pattern is related to the position of the seismic source. The shorter travel time means the velocity increase,which may be related to the regional stress accumulation.

关键词： The Menyuan,Qinghai MS6.4 earthquake Airgun excitation signal Travel time delay Wave velocity variation

Characteristics of subsurface density variations before the 4.20 Lushan M_s7.0 earthquake in the Longmenshan area: inversion results

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Earthquake Science 2015年第1期28卷 49-57页

作者： Songbai Xuan Chongyang Shen Hui Li Hongtao Hao School of Geodesy and Geomatics Wuhan University Institute of seismology China Earthquake Administration

The 4.20 Lushan Ms7.0 earthquake occurred on the southwest segment of the Longmenshan fault on 20 April 2013. Some meaningful information on the prepa- ration and occurrence of this earthquake was found based on the dynamic variation of gravity （DVG）. To examine the great progress of the Lushan earthquake, we obtained the density variation （DENV） derived from the DVG using the compact gravity inversion method in this article. The inversion results reveal three main findings：（1） the DENV in the crust in the Jinshajiang fault area changed from positive in 2010-2011 to negative in 2011-2012. （2） The DENV in the Xianshuihe fault area decreased continuously from 2010 to 2012. （3） The DENV of the uppermost mantle of South China decreased in 2010-2011 and increased in 2011-2012. We propose that the flow/expansion of the middle-lower crust beneath the Bayan Har block and Moho subsidence on the southwest margin of the Chuan-Dian block may have been the major causes of the Lushan earthquake.

关键词： Density variations Gravity inversion Deepprogress Lushan earthquake

Spectrum Deviation Method of Identification of Foreshocks or Generalized Foreshocks and Its Applications

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Earthquake Research in China 2016年第2期30卷 155-165页

作者： Yang Liming Mei Xiuping Jiang Jiajia Lanzhou Institute of seismology China Earthquake Administration

Based on previous research work,we present a spectrum deviation method to recognize a foreshock or generalized foreshock in this paper. The criterion to determine whether an event is a foreshock is a wide spectrum for an ordinary event,however,a moderate earthquake with foreshock or generalized foreshock has the characteristics of a narrow frequency band,and it deviates to the low frequency. It may be explained by metastable extension in the rupture source or related area of the main shock or regional fragmentation damage and crack nucleation process. The calculation results of two foreshocks,the M_S4. 7 event which occurred before the Yushu M_S7. 1 earthquake on April 14,2010 and the M_S5. 3 event which occurred before the Yutian M_S7. 3 earthquake on February 12,2014,show that the spectra of foreshocks shift,and they are quite different from the nonforeshock seismic spectrum of equivalent size. Therefore,this result can verify the validity of the spectrum deviation method.

关键词： Foreshocks or generalized foreshocks FFT mean square spectrumSpectrum deviation method

Study of techniques of identifying the earthquake precursory anomalies in terms of mathematical modeling

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Acta Seismologica Sinica(English Edition) 2000年第6期13卷 646-655,717页

作者：严尊国钱家栋陈俊华李胜乐 Institute of seismology China Seismological Bureau Wuhan China Center for Analysis and Prediction China Seismological Bureau Beijing China

This paper deals mainly with the key technique of identifying the anomalous signals without distortion, which might be the precursors associated with earthquakes, from the real time series of observations that would be usually the mixture of the anomalous signals, the normal background variations, some interference and noises. The key technique of 'un-biased estimation' is to construct an empirical time series and set up the criterion for identifying the anomalous variation on the bases of time series analysis. To the end of testing the method, a man-made time series including the normal variations and random interference as well as specific anomaly, has been constructed. And the test of picking up the anomaly has been conducted with the intuitive and effective way of identifying the anomalous signal from a complicated time series. Test results confirms that the techniques under discussion are effective and applicable, and the signals extracted from the analysis, could be clear and precise, and is almost similar to the known simulated anomalous signals in the experiments.

关键词： earthquake precursor time sequence anomalous identificat

Anisotropy of the apparent resistivity variation rate near the epicentral region for strong earthquakes

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Acta Seismologica Sinica(English Edition) 2001年第3期14卷 303-314页

作者： DU Xue-bin Lanzhou Institute of seismology China Seismological Bureau Lanzhou China Institute of Geophysics China Seismological Bureau Beijing China

The apparent resistivity data of 11 stations observed in or near the epicentral regions for 6 strong earthquakes are processed by the normalized monthly rate method. The result show that in the medium-short and short-imminent terms of earthquake preparation the variation rate of apparent resistivity perpendicular (or near perpendicular) to the direction of maximum principal stress is greater than that parallel (or near parallel) to the direction. Such an-isotropic phenomenon is interpreted as follow: the predominant alignment of cracks containing conductive fluid in the maximum principal stress direction caused the anisotropy of the fluid migration during the dilatancy process in the late period of earthquake preparation and resulted in the anisotropy of true resistivity variation rate for rock (or solid) medium which induced the variation rate anisotropy of apparent resistivity on the ground. The study of this paper provides some seismic examples to show the apparent resistivity anisotropy which may be helpful to study the stress status in or near the source zone in the late period of earthquake preparation of strong events.

关键词： near epicentral region strong earthquake apparent resistivity true resistivity anisotropy principal compressional stress P319

Textual research of Wudu earthquake in 186 B.C. in Gansu Province, China and discussion on its causative structure

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Acta Seismologica Sinica(English Edition) 2007年第6期20卷 696-707页

作者：袁道阳雷中生何文贵熊振葛伟鹏刘兴旺刘百篪 Lanzhou Institute of seismology China Earthquake Administration Earthquake Administration of Jiangsu Province

On the basis of the textual research on the historical earthquake data and the field investigation of Wudu earthquake occurred in 186 B.C., we suggest that the earthquake parameters drawn from the present earthquake catalogs are not definite and amendments should be made. The heavily-damaged area of this earthquake should be located between Jugan township of Wudu County and Pingding township of Zhouqu County. Its epicenter should be in the vicinity of Lianghekou in Wudu County with a magnitude of about 7-7 1/4 and an intensity of about IX-X. The major axis direction of the heavily-damaged area should be in the WNW direction that is approximately consistent with the strike of the middle-east segment of Diebu-Bailongjiang active fault zone, and the origin time should match up to that of the latest paleoearthquake event [before （83±46） B.C.] obtained by the trench investigation. Certain seismic rupture evidences are still preserved on this fault segment. Therefore, we propose on the basis of comprehensive analysis that the causative structure of the M 7-7 1/4 Wudu earthquake in 186 B.C. should be in the middle-east segment of Diebu-Bailongjiang active fault zone.

关键词： Wudu earthquake in 186 B.C. textual research of historical earthquake causative structure Diebn-Bailongjiang fault zone

Research on variety characteristics of China's Mainland troposphere based on CMONOC

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Geodesy and Geodynamics 2018年第5期9卷 411-417页

作者： Hongbo Shi Rui Zhang Zhaosheng Nie Yu Li Zhengsong Chen Tan Wang China Earthquake Networks Center Institute of seismology China Earthquake Administration

In this research, we processed the GPS and meteorological data from about 220 stations of Crustal Movement Observation Network of China(CMONOC) observed in 2014 and derived the Zenith Total Delay(ZTD) map in both spatial and temporal dimension. The results of ZTD have high accurate and reliable as IGS and all sites with varying locations show obvious variety characteristics of Chinese mainland. Meanwhile, the precipitable water vapor(PWV) correlation coefficients between GPS observation and upper air sounding is close to 1, and the comparison of GPS-derived PWV and observed PWV from meteorological sites indicating GPS observation data generated in CMONOC project applied to the weather forecast research is feasible. In addition, based on all stations covered the whole Chinese land area and using interpolation algorithms, we make contour plots of PWV distribution per hour. We observe obvious feature that the precipitable water in north and western area is less than south and east area all over this year. High latitudes area may be dry and low latitudes area is wet.

关键词： GPS CMONOC Precipitable water vapor Troposphere ZTD

General geochemistry of rare earths in the central region of the Dniester river basin,Republic of Moldova

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Journal of Rare Earths 2010年第S1期28卷 513-516页

作者： Aurelia Popuiac Institute of Geology and seismology of Academy of Science of Moldova 60/3 Gh.Asachi StreetMD 2028ChisinauRepublic of Moldova

In the central region of the Dniester river basin,over several decades,a complex geological study aimed at determining metal-logenic particularities of geological formations in this area was carried *** on geological and geochemical data obtained by the Insti-tute of Geology and seismology of the ASM and the State Geological Agency of Moldova(AGeoM),in the central basin of the Dniester river detection of mineralization of the radioactive elements,rare metals,iron,zinc,lead,barite,including the rare earths,was already being con-sidered perspective.

关键词： Dniester river basin terrigenous layers rare earths

A　preliminary　research　establishing　the　present-time　intraplate　blocks　movement　model　on　the　Chinese

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Acta Seismologica Sinica(English Edition) 1998年第4期11卷 403-412页

作者： Zhou, Shuo-Yu Zhang, Yue-Gang Ding, Guo-Yu Wu, Yun Qin, Xiao-Jun Shi, Shun-Ying Wang, Qi You, Xin-Zhao Qiao, Xue-Jun Shuai, Ping Deng, Gan-Jin Institute of seismology China Seismological Bureau Wuhan China Center for Analysis and Prediction China Seismological Bureau Beijing China

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关键词： present-time intraplate the establishing Chinese