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Wang M.,China Earthquake Administration | Lou W.,China Earthquake Administration | Li P.,China Earthquake Administration | Li P.,Institute of Earth quake Science | And 2 more authors.
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

A major geomagnetic storm occurred on July 15-16, 2012, which is characterized by a long-lasting southward turning of interplanetary geomagnetic field (IMF) for ~30. h below -10. nT. Prominent large-scale ionospheric disturbances were observed in North China during this extreme space weather event. This study reveals the possibility of using the newly built China seismo-ionospheric ground-based monitoring network (CSGMN) to investigate the ionospheric storm effect during different phase of the storm. As a main part of the CSGMN, the oblique and vertical sounding systems and global position system (GPS) network all observed a moderate and a strong positive storm effects around the noon and the sunset sector on 15 July. The maximum enhancement of parameter peak electron density (NmF2) increased 100% and TEC 60%. The positive phase then is followed by an intense negative storm effect during the entire day on July 16 with NmF2 and TEC fell below 40% of the previous quiet day values. Also, the electron density profiles retrieved from the COSMIC radio occultation measurements were examined and validated with the ground measurements in order to estimate the possibility of its use as an additional data source to study altitude distribution of ionospheric storms. Good agreement has been reached between the ground and satellite occultation measurements even if they are not close. The result here shows that CSGMN can be a very powerful network not only for the seismo-ionospheric study but also in monitoring space weather. © 2013 . Source


Tu J.,Harbin Institute of Technology | Liu H.,National Earthquake Infrastructure Service | Tang A.,Harbin Institute of Technology | Zheng T.,China Earthquake Administration
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015

The acceleration response can be used to analyze the mechanisms of a landslide and to determine the coefficients of earthquake influence reasonably. The centrifuge shaking table test of 50g modelling the colluvial landslide was carried out. The landslide model was placed in a rigid aluminum alloy container with the length of 600 mm, width of 400 mm and height of 500 mm. The bedrock wave recorded at Qingxi station during the Wenchuan earthquake was exerted from the bottom of the model. The amplification coefficients of the horizontal and vertical peak ground acceleration(PGA) at landslide surface were found to increase with the increasing of the elevation. The increasing rate of the amplification coefficients of PGA at the measured spots near the slope crest was notably larger. The acceleration response at the slope surface was significantly different from that inside the landslide. The horizontal acceleration at bedrock had the amplification effect along the elevation of the landslide, but was much smaller than that at the landslide surface. A phenomenon of wave mode transformation was found at the crest of the landslide. The amplification coefficients of PGA at the crest of landslide increased firstly and subsequently decreased with the increasing of the amplitudes of the input seismic wave. ©, 2015, Academia Sinica. All right reserved. Source


Tu J.,Harbin Institute of Technology | Liu H.,National Earthquake Infrastructure Service | Tang A.,Harbin Institute of Technology | Zheng T.,China Earthquake Administration
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2016

Centrifuge shaking table model test of colluvial landslide reinforced by cantilever anti-slide pile was designed and carried out on a centrifuge shaking table at 50 gravitational accelerations in order to research its seismic response, the distribution regularity of dynamic soil pressure after pile and dynamic bending moment of the anti-slide pile. During the processing of the model test, bedrock wave(Qingxi wave) was inputted from the bottom of the model by scaling the amplitude of the input seismic wave. The seismic performance of colluvial landslide reinforced by cantilever anti-slide pile under earthquakes of different intensities is studied by monitoring the acceleration response of landslide at different positions, the dynamic soil pressure after pile and the strain of the anti-slide pile. Results show that the acceleration response of landslide increases with the increasing height of landslide. The landslide shows an obvious elevation amplification effect, i.e., the increasing rate of the peak ground acceleration(PGA) amplification coefficients becomes notably larger approaching the slope crest, and the acceleration response characteristic of the landslide surface shows the surface effect under earthquake. The dynamic response of the soil is restricted by anti-slide pile to a certain degree. The dynamic soil pressures after pile rapidly increase to peak value and then keep roughly stable along with the excitation of earthquake motion. And they will form dynamic soil pressures to act on the anti-slide pile. The maximum dynamic bending moment of the pile appears near the bedrock surface, which the distribution rule reflects the convex form. Both the dynamic soil pressure after pile and dynamic bending moment of the pile will increase with the increasing the strength of seismic wave. The results provide a good foundation for seismic design of the cantilever anti-slide pile. © 2016, Science Press. All right reserved. Source


Xiang L.,CAS Wuhan Institute of Geodesy and Geophysics | Xiang L.,University of Chinese Academy of Sciences | Wang H.,CAS Wuhan Institute of Geodesy and Geophysics | Steffen H.,Lantmateriet | And 4 more authors.
Earth and Planetary Science Letters | Year: 2016

Understanding groundwater storage (GWS) changes is vital to the utilization and control of water resources in the Tibetan Plateau. However, well level observations are rare in this big area, and reliable hydrology models including GWS are not available. We use hydro-geodesy to quantitate GWS changes in the Tibetan Plateau and surroundings from 2003 to 2009 using a combined analysis of satellite gravity and satellite altimetry data, hydrology models as well as a model of glacial isostatic adjustment (GIA). Release-5 GRACE gravity data are jointly used in a mascon fitting method to estimate the terrestrial water storage (TWS) changes during the period, from which the hydrology contributions and the GIA effects are effectively deducted to give the estimates of GWS changes for 12 selected regions of interest. The hydrology contributions are carefully calculated from glaciers and lakes by ICESat-1 satellite altimetry data, permafrost degradation by an Active-Layer Depth (ALD) model, soil moisture and snow water equivalent by multiple hydrology models, and the GIA effects are calculated with the new ICE-6G_C (VM5a) model. Taking into account the measurement errors and the variability of the models, the uncertainties are rigorously estimated for the TWS changes, the hydrology contributions (including GWS changes) and the GIA effect. For the first time, we show explicitly separated GWS changes in the Tibetan Plateau and adjacent areas except for those to the south of the Himalayas. We find increasing trend rates for eight basins: [Formula presented] for the Jinsha River basin, [Formula presented] for the Nujiang-Lancangjiang Rivers Source Region, [Formula presented] for the Yangtze River Source Region, [Formula presented] for the Yellow River Source Region, [Formula presented] for the Qaidam basin, [Formula presented] for the central Qiangtang Nature Reserve, [Formula presented] for the Upper Indus basin and [Formula presented] for the Aksu River basin. All these increasing trends are most likely caused by increased runoff recharges from melt water and/or precipitation in the surroundings. We also find that the administrative actions such as the Chinese Ecological Protection and Construction Project help to store more groundwater in the Three Rivers Source Region, and suggest that seepages from the Endorheic basin to the west of it are a possible source for GWS increase in this region. In addition, our estimates for GWS changes basically confirm previous results along Afghanistan, Pakistan, north India and Bangladesh, and clearly reflect the excessive use of groundwater. Our results will benefit the water resource management in the study area, and are of particular significance for the ecological restoration in the Tibetan Plateau. © 2016 The Author(s) Source


Liu Y.,China Earthquake Administration | Zhao J.,National Earthquake Infrastructure Service | Liu P.,National Earthquake Infrastructure Service
Journal of Natural Disasters | Year: 2015

In this paper, Chuanqing block and its surrounding three main active faults, including Xianshuihe fracture zone, Longmenshan fracture zone and Dongkunlun fracture zone, were taken as research object. Based on data for tectonic stress field, GPS monitsring, geology historical earthguaks, and state-related friction canstitutive relation. The mechanics and motion states of faults - blocks before and after the recent destructive earthquakes-Kunlunshan earthquake, Wenchuan earthquake, Yushu earthquake and Lushan earthquake were simulated. The results show that there are relations between stress, strain, displacement states and earthquake. Strong earthquakes may happen in Ganzhi-Daofu segment of Xianshuihe fracture zone, southwest and northeast segments of Longmenshan fracture zone in the future according to preliminary inference. Source

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