Feng J.-G.,Lanzhou Institute of Seismology |
Zhang H.,Lanzhou Institute of Seismology |
Yang P.,Lanzhou Institute of Seismology |
Yang P.,China Earthquake Administration
Earthquake | Year: 2016
Based on seismic data from the Gansu seismic network since 1990, we calculated b values and Δb values in the epicentral region before the 2013 Minxian-Zhangxian MS6.6 earthquake. The results show that the earthquake occurred at the margin of significantly low b value area in southeastern Gansu, and before earthquake the area around the epicenter has significantly abnormal Δb values. From the earthquake and the spatial distribution of lower b values, this earthquake does not decrease the possibility of dangerous strong earthquake does not decrease the possibility of dangerous strong earthquake to occur in this region. © 2016, Science Press. All right reserved.
Huang J.,Lanzhou Institute of Seismology |
Wan Y.-G.,China Institute of Technology
Earthquake | Year: 2015
The capital region of China emplaces dense seismic network in recent years, it is possible to solve small focal mechanisms. We gathered large earthquake focal mechanisms in last fifty years and moderate or small earthquake focal mechanisms between 2002 and 2004, and calculated the present tectonic stress field of the capital region by the grid search method, which weighs different sized earthquakes and can improve the accuracy of the stress field inversion. The analysis of inversion results of different sub-region show that the direction of the maximum principle compressive stress axe is toward N (43°~86°) E in the Beijing-Zhangjiakou-Datong region, toward N (38°~86°) E in Tangshan area, and toward N (79°~81°) E in Xingtai area. Inversion results of this paper are similar with previous results, and reflect the correctness of the approach. The results reveal the stress field distribution consistency and sub-region difference in the capital region, and can provide reference for earthquake mechanism explanation and geodynamics research. ©, Science Press. All right reserved.
Wu Z.-J.,China Earthquake Administration |
Wu Z.-J.,Lanzhou Institute of Seismology |
Chen T.,Chinese Academy of Sciences |
Ma W.,Chinese Academy of Sciences
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013
The dry bridge, named bridge instead of embankment, has been widely adopted in regions with high temperature and instable permafrost or those with high ice content permafrost along the Qinghai-Tibet railroad. In order to obtain the dynamic response characteristics of typical embankments and dry bridges under the effect of vibration loads of trains in permafrost regions, strong motion tests on the filld embankment at the Beilu River segment and the bridge pile foundation of the Qingshui river Bridge in permafrost regions are carried out. The acceleration waveforms under running of freight and passenger trains are acquired from the tests, and the attenuation laws of vibration response, energy of vibration response and natural frequency are obtained by analyzing the acceleration response and FFT spectrum response. The test results show that there is an obvious damping effect during the transfer process. This study is of great significance to the stability analysis and prediction of the Qinghai-Tibet railroad.
Liu F.B.,Lanzhou Institute of Seismology |
Wang A.G.,Lanzhou Institute of Seismology |
Wang A.G.,Lanzhou base of Institute of earthquake Science
Applied Mechanics and Materials | Year: 2014
On July 22, 2013, an Ms6.6 earthquake occurred in Minxian-Zhangxian, Gansu Province, China, which caused serious damages. Because of the abundance and clear relationship with the main shocks, aftershocks sequences are typical types of behavior and provide useful data sets. To better understand the aftershocks triggering by static stress changes of the main earthquake, based on Okada's elastic half-space model, we used accept fault plane consistent with the source and accept fault plane as the optimal models to calculate the stress changes on aftershock focuses by the Minxian-Zhangxian 6.6 Earthquake respectively. The results show that the latter model is better than former, more than 90% of aftershocks located in NWW and SEE, the stress increased areas, which is consistent with strike of Lintan-Tanchang fault (LTF), in other words, the Coulomb static stress changes of the main shock can induce the aftershocks. © (2014) Trans Tech Publications, Switzerland.
Sun J.,Lanzhou Institute of Seismology |
Wu Z.,Lanzhou Institute of Seismology |
Liu K.,Key Laboratory of Loess Earthquake Engineering
6th Japan-China Geotechnical Symposium, SJGS 2015 | Year: 2015
Here we hoped to understand loess dynamic deformation through analyzing the physical process and mechanical mechanism. Therefore, we introduced a concept of stress ratio and proposed its mathematical formula to disclose the three-stage feature of loess dynamic strain hiding inside a series of laboratory data. By applied Mohr-Coulomb failure criterion, the stress ratio could consider three aspects of influence factors, i.e. structure strength of soil, consolidation pressure in actual field and seismic loading onto the soil. To a certain extent, the stress ratio could reveal the relative tolerability of loess soil under seismic loadings. Based on three-stage features of loess dynamic deformation, we obtained an empirical relation between stress ratio and compression value of void ratio. Then combined with a theoretical relation of dynamic residual strain, initial void ration and compression value of void ratio, we provided a semi-empirical model to estimate the dynamic residual strain of unsaturated loess.
Wang L.,Lanzhou Institute of Seismology |
Sun J.,Lanzhou Institute of Seismology |
Huang X.,Lanzhou University of Technology |
Xu S.,Lanzhou Institute of Seismology |
And 4 more authors.
Soil Dynamics and Earthquake Engineering | Year: 2011
At present piles foundation is widely used in the earthquake-prone loess area of China. Unfortunately, negative skin friction (NSF) along piles induced by an abrupt settlement of loess under strong earthquakes, so called seismic subsidence, has not been taken into account in design of piles foundation due to the lack of NSF data from field test. In order to investigate NSF along piles caused by seismic subsidence of loess and develop a method to estimate this earthquake-induced NSF, the authors perform a field test at a loess site by means of a series of explosions, i.e. a short delay blasting, in which two reinforced concrete piles was grouted. The expected ground motion generated by the short delay blasting is strong enough to induce an obvious seismic subsidence in the loess site. There are 40 stress gages to be averagely disposed into the two piles with a certain interval to collect the data of NSF during this field test. Meanwhile, ground motion and seismic subsidence of loess were, respectively, observed by accelerographes and a level gauge. The obtained data particularly disclose the developing characteristics and magnitude of loess seismic subsidence and NSF at the condition of strong ground motion. The loess seismic subsidence and NSF both have a rapid development in the explosion process and then keep a slower increase for some days after the blasting. At the end of observation, the maximum seismic subsidence of loess in the field reaches 33. mm; the average NSF along piles attains to 54. kPa, which is much greater than previous cases of NSF caused by collapse of loess. This field test shows the NSF along piles induced by seismic subsidence of loess is significant and should not be ignored in design of piles foundation in seismic loess regions. © 2010 Elsevier Ltd.
Guo X.,Lanzhou Institute of Seismology |
Guo X.,Prediction Institute |
Zhang Y.-S.,Lanzhou Institute of Seismology |
Zhang Y.-S.,Prediction Institute |
And 3 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2010
Based on the outgoing long-wave radiation data of geostationary satellite and their variation characteristics, this paper proposes a method for extracting earthquake thermal infrared anomaly, namely, the relative variance rate of power spectrum estimation. The proposed method is applied to analytical study of OLR for the Wenchuan earthquake and other five Ms ≥ 6. 5 earthquakes in Mainland China. The results indicate that the power spectrum amplitude of OLR increased to different degrees before the great earthquakes. Characteristic period and characteristic amplitude are short and small in moist (low altitude) areas respectively, while the period and amplitude are long and big in arid (high altitude) areas respectively. The characteristics of observed thermal infrared anomalies are easy to be recognized. The method is very effective for extracting and analyzing earthquake-related information.
Jia G.,Lanzhou Institute of Seismology |
Yuan Z.,Lanzhou Jiaotong University |
Zhong X.,Lanzhou Institute of Seismology |
Xia K.,Lanzhou Institute of Seismology
World Information on Earthquake Engineering | Year: 2010
Rural self-built brick masonry houses usually have poor seismic performance because of irregular design and construction. Taking Ms8.O Wenchuan earthquake as an example, rural. self-built brick houses in representative region at different intensity zones are selected as object to analyze characteristics of seismic damage. The seismic damage to walls, roof and non-structural components of rural brick houses are analyzed at different intensity zones by means of using quantified technical terms to describe seismic damage. Meanwhile, damage features of the kinds of rural houses are obtained under seismic action, in which only the vibration failure is considered. At last, advices for reducing seismic damage to the rural brick houses are given.
Tian X.,Lanzhou Institute of Seismology |
Zhang X.,Lanzhou Institute of Seismology |
Zhao L.,Lanzhou Institute of Seismology
Advanced Materials Research | Year: 2013
UPS (Uninterrupted power supply) is a basis for the observation equipments, and its reliability play a decisive role for the all tasks. Most of the observation stations are unattended, and their distribution is dispersive. So the maintenance of UPS is tedious and complicated, and it is difficult to achieve unified management and effective maintenance. In response to this situation, this paper proposes a UPS remote intelligent monitoring program. Through the monitoring data collection, remote data transmission, data output display and the control command transfer, this program can monitor the power supply capacity, load conditions and working status in the real-time, and achieve the function of automatic alarm and remote switch control. It completely changes the traditional decentralized management model and improves the level of scientific management of the UPS. © (2013) Trans Tech Publications, Switzerland.
Lanmin W.,China Earthquake Administration |
Nai W.,Lanzhou Institute of Seismology |
Nai W.,Petrochina |
Qian W.,Lanzhou Institute of Seismology
15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability | Year: 2015
Earthquake induced landslides were one of major causes for a large number of deaths and huge economic loss in the Loess Plateau. In order to evaluate the influencing area of seismic landslides, we presented a method of predicting sliding distance of seismic landslides in Loess Plateau by means of fuzzy information model based on 93 cases data of seismic loess landslides. Firstly, the types, characteristics, and influencing factors of seismic landslides in Loess Plateau were studied based on field investigation, back analysis and laboratory tests. Secondly, Morgenstern-Price method was used for calculating the seismic stability of loess slopes. The relationships between safe factor and influencing factors were established, which include seismic intensity, relative altitude, slope angle, unit weight, internal cohesion, internal friction angle. Furthermore, the factors of influencing sliding distance of landslides were figured out. Thirdly, a fuzzy information matrix was established based on 93 loess seismic landslides caused by South Tianshui 8.0 earthquake in 1654, Tong Wei 7.5 earthquake in 1718, Haiyuan 8.5 earthquake in 1920 and Gulang 8.0 earthquake in 1927. And then a fuzzy information model was developed for calculating sliding distance and influencing area of seismic loess landslides. Fourthly, the influencing areas of 22 potential landslides in Tianshui city were respectively predicted. The predicted results shown that the method presented in the paper is more accurate for seismic loess landslides, comparing with other methods.