Shijiazhuang, China
Shijiazhuang, China

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Fu Z.-X.,Institute of Earthquake Science | Lu X.-J.,Institute of Earthquake Science | Zhang Y.-S.,Lanzhou Institute of Seismology | Jin X.-S.,Hebei Seismological Bureau | Zhao H.-C.,Shanxi Seismological Bureau
Earthquake | Year: 2010

There are relatively active strong seismicity inside the second-order Lasa and Qiangtang blocks compared with other blocks in the first-order Qing-Zang active block region, which might be related to the weaker crust strength due to thicker crust, higher heat and lower shear strength on normal fault there. Inside the second-order Lasa and Qiangtang active blocks, cases of abnormal heat phenomenon have been observed before two strong earthquakes(M7. 3 Yutian earthquake and M6. 6 Danxion earthquake in 2008) , which might be related to the dilatation in the faults of earthquake preparation region and nearby, where melting material and liquid enter into from the low velocity layer in uppermiddle crust.

Li B.-K.,China Earthquake Networks Center | Diao G.-L.,Hebei Seismological Bureau | Xu X.-W.,China Earthquake Administration | Wan Y.-G.,Beijing Institute of Technology | And 3 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015

The location parameters of the Zayü, Tibet M8.6 earthquake sequence in 1950 in the published catalogues are poor, which cannot help further study of this great event. In order to provide more precise location results and some features of their spatial-temporal distributions, and to reveal the stress field in the corresponding region, we attempted to relocate this earthquake sequence and to determine the focal mechanisms. The data of global seismic stations from International Seismological Summary (ISS) and the Catalogue of China Earthquakes (BC 1831─AD 1969) were collected. The 16 events with M≥6 of the Zayü, Tibet M8.6 sequence were relocated by P arrivals at 239 worldwide stations using the routine location method and model of Chinese National Seismographic Network: Improved Geiger and the JB time tables. The corresponding fault plane solutions and composite fault plane solutions were determined by first motions of P waves based on the new relocations. (1) The relocations of 16 strong earthquakes of the Zayü M8.6 sequence have been completed. It is shown that the epicenters in different periods appeared in different sub-regions: A foreshock which occurred on 23 Feb 1950 appeared in the 1st sub-region, the top of the great bend of the Yarlung Zangbo River, which lies at the north of Motuo. The mainshock and the following 7 aftershocks in 3 days which occurred from 15 Aug 1950 to 18 Aug 1950 were located in the 2st sub-region near Zayü and distributed along the north-west belt. The 3 aftershocks in period 3 which occurred from 22 Aug 1950 to 13 Sep 1950, were located in the 3st sub-region extending to the south, India and Myanmar. The 3 aftershocks in period 4 which occurred from 30 Sep 1950 to 15 Apr 1951 appeared in the 4st sub-region at Motuo and Cuona, west of the aftershock epicenter area. Another aftershock occurred on the 110th day after the mainshock, the epicenter of which returned to the place near the mainshock. (2) The focal mechanism solutions determined based on the relocations indicate that the NWW strike of a nodal plane of the mainshock is consistent with the NWW direction of the major axis of the aftershock epicenter area in the 2st sub-region. All compressive axes P and tensional axes T of the earthquake sequence are nearly horizontal, of which most dip angles are less than 20°. The compressive axes of the mainshock and the aftershocks in the 2st sub-region are nearly north-south direction, and tension axes are nearly east-west direction. But in the 3st and 4st sub-region, the compressive axes of aftershocks are nearly east-west direction, and tensional axes are nearly north-south direction. The 16 events of the Zayü, Tibet M8.6 earthquake sequence in 1950 have been relocated. The new results are quite different from the parameters in the previous catalogues of which the locations of many aftershocks were exactly the same as the mainshock, i.e. only one point. The relocations indicate that the epicenters in different periods appeared in 4 different sub-regions rather than distributing along the determined rupture. The obvious correlation of these 4 sub-regions is clockwise rotation movement. The focal mechanism solutions determined based on the relocations display that the differences of focal mechanisms among the aftershocks of the sequence are large. © 2015, Science Press. All right reserved.

Niu L.,Hebei Seismological Bureau | Zhu R.,Petrochina | Wang L.,Hebei Seismological Bureau | Bai B.,Petrochina | And 2 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2015

China is rich in shale gas resources. A breakthrough has been made in the exploration and development of Lower Paleozoic marine shale gas and Mesozoic continental shale gas in the south of China. In terms of the Meso-Neoproterozoic paleo-shale widely distributed in North China, many previous studies are focused on the characteristics of source rocks, but not on shale reservoirs. Through whole rock and clay mineral X-ray diffraction analysis, geochemical analysis, mercury penetration, nitrogen (N2) and carbon dioxide (CO2) adsorption analysis in combination with ESEM and FESEM observations, relevant evaluation and research was performed on clay mineral composition, TOC content, maturity, and pore type characteristics of reservoirs for the shale in Meso-Neoproterozoic Chuanlinggou Formation, Hongshuizhuang Formation and Xiamaling Formation, Jixian, Tianjin,. The results indicate that mineral compositions of the sample mainly consist of quartz and clay minerals, of which the content is 20.3-52.3% and 38.4-54.1% respectively, TOC content is 0.008-3.44%, and Ro values are ranged in 1.44-3.01%. The pores are relatively developed in these samples, which mainly include inter-grain and dissolution pores, organic marginal pores, intra-grain and dissolution pores, inter-crystal pores in clay minerals and so on. According to a comparative analysis on three sets of shale, it is considered that the shale reservoirs are most favorable in Hongshuizhuang Formation, followed by Xiamaling Formation and Chuanlinggou Formation. ©, 2015, Shiyou Xuebao/Acta Petrolei Sinica. All right reserved.

Fu Z.-X.,Institute of Earthquake Science | Lu X.-J.,Institute of Earthquake Science | Jin X.-S.,Hebei Seismological Bureau | Zhao H.-C.,Shanxi Seismological Bureau | And 2 more authors.
Earthquake | Year: 2010

This paper comparatively discusses the active fault slip rates of 8 great intra-continental shallow thrust earthquakes occurred in the East Asia Triangular Seismic Region based on the collected slip rate data. Preliminary analysis shows that the average vertical slip or shortening rates on the shallow thrust faults are less than 12 mm/a in the region . The great Wenchuan M s8. 0 earthquake of May 12, 2008, Sichuan province, China, occurred in the Longmen Shan active fault with abnormal low slip rate(0. 2 -1.0 mm/a). The relationship between earthquake magnitude and slip rate is not linear simply. Earthquake magnitude might be related to the geological ages, scale(length, width and depth) , rate and history,medium property, stress-strain relation and geodynamic condition of the earthquake faults, which needs further and deep study.

Zhang Y.,China Earthquake Networks Center | Gao F.,China Earthquake Networks Center | Ping J.,Hebei Seismological Bureau | Zhang X.,China Earthquake Networks Center
Natural Hazards | Year: 2013

China Metropolitan area around Beijing is one of the earthquake test sites in Continental China. Through more than 20 years of hard work, abundant seismic, geological, geophysical and geochemical data have been obtained, and the variation of seismic, geophysical and geochemical parameters was recorded before several strong earthquakes and some moderate earthquakes in this area. In this paper, we chose 19 high qualified observatory parameters in this area to establish a multidisciplinary system for earthquake forecast, including apparent resistivity, ground water level, ground-level, tilt, radon content in groundwater, volumetric strain, Hg content in groundwater, low frequency electric signal. We calculate the synthetic information by a simple algorithm. The procedure is: firstly, we detect the abnormal intervals of the observatory data by some data analysis methods such as filtering, differencing, etc.; secondly, we endow the value of 1 to the abnormal intervals and 0 to other intervals and produce a new time series of data set of the ith parameter; thirdly, we compose the value of the new time series of 19 observatory parameters and obtain the normalized value as called synthetic information. The result shows that there are high correlations between the high synthetic information and the earthquakes with M ≥ 5.0 in this area. The earthquakes almost occurred several days to several months after the peak value of the synthetic information. This synthetic method might be taken for a short-term prediction method for M ≥ 5.0 earthquakes in this area. © 2011 Springer Science+Business Media B.V.

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