MIN Xiang-yi , YAO Kai , HE Xin-she
2003, 25(4):289-292,318.
Abstract:Minle-Shandan MS 6.1 earthquake occurred on Oct. 25, 2003. in west of Gansu province. Just before the earthquake 4 digital mobile strong motion instruments were erected in Hexi region, near the epicenter, by Lanzhou Institute of Seismology, according to the definite prediction opinion of the Institute. One instrument of them in Minle mobile station obtained the near-field strong motion seismic record of main shock. The distance to epicenter is 12.6 km. The maximum acceleration on direct EW is 331 cm/s2; on NS is 332 cm/s2 and on UD is 209 cm/s2. Furthermore some immobile strong motion stations in Hexi region (Shandan, Sunan and Wuwei)also obtained this event. In the paper the observed near-field frequency spectrum of main shock and the acceleration attenuation equation for Hexi region, Gansu province, are discussed based on the data of MS 6.1 main shock and MS 5.8 aftershock.
LIU Xu , ZHU Yuan-qing , TONG Yu-xia
2003, 25(4):293-297.
Abstract:On the hypothesis that for a given correlation coefficient and a distance between two substations, there will be a referent correlative wavelength, and all the changes of correlation caused by frequency and epicentral distance can be regarded as changes of the apparent wavelength. For near events, there are no ideal correlation coverage of the distances among substations.In the case.using the gain formula reported by S. Mykkeltveit etc.to forecast signal-noise ratio gain of beam-form is proposed, without restriction on array configuration.The method appears to fit for our data.Some differences between a regional array and for far enent one are discussed.
WANG Hai-jun , JIN Ping , LIU Gui-zhong , WANG Xiao-ming
2003, 25(4):298-303.
Abstract:In automatic processing of seismic records, based on the method of autoregressive Akaike information criteria(AIC) and the amplitude ratio between signal and noise, a hybrid method for estimating arrival time of seismic phase is presented in this paper. Using the curve of AIC and the curve of amplitude ratio a new curve is constracted, which is transformed by a similarly rotation of coordinate.The new curve can accurately estimates arrival time of signal in automatic processing, especially for later phases(such as S-wave, Lg-wave) with low ratio of signal and noise. The arrival times for 23 seismic P-phases and later phases recorded at WMQ station in CDSN are picked by the new method. In comparison of manual result, the root mean square error of P-phase is 0.71 second, and one of later phase is 1.64 second, which is better than the result obtained by traditional AIC algorithm.
XIAO Lan-xi , ZHU Yuan-qing , TAO Jiu-qing , DU Xian-song
2003, 25(4):304-311.
Abstract:Under the restriction of GPS observation data and results from seismological study, in two models of China continent lithosphere which have different viscosity coefficients, the relationship between the intensity of plate driving force on the plate boundery and the viscosity coefficients of model is numerical simulated.The geodynamic driving mechanism of continental lithosphere movement in China by the India-Eurasia plate collision is discussed.The geodynamics driving characteristics of the India-Eurasia plate collision and action forces in vertical direction, which include geopotential of Tibetan Plateau landform and buoyancy of heat convection in its upper mantle, are presented.The intensity ratio of driving force to China continental lithosphere from India plate, Pacific plate and Philippines plate is about 4:1.25:1. The driving force of continental collision forms high horizontal compression stress in hard layers and the vertical force forms high horizontal compression stress in weak layers.The vertical force blocks the crustal movement to the north in the south part of Tibetan Plateau, and enhances mass extrusion in the north-east part of Plateau.
LI Tie-ming , DENG Zhi-hui , LUI Yi-pei , LIU Ben-pei
2003, 25(4):312-318.
Abstract:Global Positioning System(GPS) network on north section of Xianshuihe fault is arrayed in 1991 and measured 3 times in 1991, 1996 and 2000.The result shows that:(1) The displacement velocity increase regularly from Xialatuo station in rate of 8.5 ±0.8 mm/yr with SE direction to Qianning station in rate of 13.8±1.7 mm/yr with EW direction along the fault.(2) On the Daofu measure profile which cross the fault, the velocity rise as stations are far from the fault on the SW wall of fault.(3) The relative movement of the stations on two walls of the fault is little so we infer that at present the slip rate of the Xianshuihe fault is not obvious that is in accordance with the conventional geodetic data along the fault. As the conclusion, in the period of minor activity of Xianshuihe fault, the Chuandian and Chuanqing plates should be thought as a whole when studing its seismic hazard, in other time we should put our studying focal on the activity of the fault and the relationship with the seismic hazard.
QIN Bao-yan , YAO lan-yu , SHAO Yong-xin
2003, 25(4):319-325.
Abstract:Using seismicity data, the pregnant construction and the process of the Jiji strong earthquake in 1999, Taiwan, are studied.The possibility of prediction for Jiji earthquake is discussed by using the combination model and time characters of remarkable earthquakes in the pregnant process.
YANG Shi-sheng , LI Liu-ying , MO Jing-ye , AN Lin , LI Geng-ming , WU Shi-ping , WANG Ling
2003, 25(4):326-330,337.
Abstract:Based on the earthquake record data of Guangxi seismic network in more than 30 years, the ambient shear stress values around many middle and small earthquake sources in Guangxi and adjacent rigions are determined by using the method of half period in P wave first impulse and magnitude.Evolvement characters of the ambient stress values before and after 8 moderate-strong earthquakes in Guangxi is studied.
ZHANG Su-ping , WANG Lan-min , MA Er-man
2003, 25(4):331-337.
Abstract:On the bases of predecessors's research work and comprehensively analyzing the seismic geology, topographic features, active faults and site factors, the microzonation of seismic geological disaster for Jingtai town, Gansu province, is down by using the technique of GIS and neural network model. The result shows that the method turns previous qualitative indexes into quantitative one, and realizes computer drawing figure automatically. The work outcome can be showed accurately and directly.
2003, 25(4):338-343.
Abstract:It is found that the phenomenon of concentration of medium-strong earthquakes before M ≥ (7.0) exists in 20th century in Yunan province.A flexible time prediction of main earthquakes can be made on the basis of the features of concentration of medium-strong earthquakes, and the epicenter of potential main earthquake can also be predicted through the study combining with "the earthquake in quiescence".At the end, the mechanism of relation between the foreshocks and main shock is discussed.
MA He-qing , ZHAO Wei-ming , ZHANG Wen-xiao , JIN Chun-hua
2003, 25(4):344-347,369.
Abstract:Deeper discussion on the seismicity acceleration model is made in this paper. A direct solution to the time-crack equation of the model is given. Using the model, the prediction tests for moderate-strong earthquakes occurred in Gansu, Ningxia, Qinghai, Xinjiang and Inner Monglia provinces and autonomous regions in north-west of China from 1970 are made and earthquake predication in future 1~3 years for this rigion is given.
XIAO Li-zhu , YANG Li-ming , LI Chun-yan , ZHANG Xiao-mei , ZHANG Ying
2003, 25(4):348-353.
Abstract:Based on the division of active blocks in northern Qinghai-Tibet plateau, the full spatio-temporal scan for seismic frequency of small earthquakes in every blocks since 1970 is down to study short-impending anomaly characteristics.The result indicates that the corresponding ratios of the anomalies of seismic frequency to MS ≥ 5.0 earthquakes are different in different blocks, owing to various regional tectonics, but the most of starting time, ending time and maximal (or minimal) value of positive and negative anomalies for small seismic frequency appeare one to six months before medium-strong earthquakes. And the result is checked up statistically by using R value, the eligibility rate(R ≥ R97.5%) in the region is 69%, and the general Eligibility rate of R-value for inner and adjacent regions is 94%.
CHAI Chi-zhang , MA He-qing , JIN Chun-hua
2003, 25(4):354-358.
Abstract:In this paper, Qilian Mt.-Liupan Mt. earthquake belt is divided into three sections:the east, the middle and the west section.The migration features of moderate-strong earthquakes among sections are studied, and the statistical study on seismicities of every section is done also. So the migration regulations and the anomalous features before moderate-strong earthquakes in three sections of Qilian Mt.-Liupan Mt. earthquake belt are obtained.
LIU Xiao-feng , MEI Xiu-ping , ZHANG Xiao-mei
2003, 25(4):359-364.
Abstract:Three seismic windows with mid-short period prediction effectiveness are selected through a study on seismicity in North areas of Qinghai-Xizang plateau. The anomalous feature in the seismic windows before strong earthquake(MS >5.0)is analyzed and the half-quantity predition criteria for midshort period are attained. The result shows that 80% anormalous occur 1 to 6 mouthes before strong earthquake, so we consider 1~6 months as strong event time after some anomalous occur in the mid-point of seismic windows. There is no intimate relationship between the anomal amplitude and the follow ing earthquake. The Gulang seismic window is corresponding with the earthquake in large and shear strike-slip fault, The main anomalous in Zhouqu and Wuhai windows is corresponding with the earthquake in constrain thrust fault in the internal plateau. But there is no apparently relationship between the earthquake(5.0 < Ms < 6.0)and anomalous in seismic windows.
2003, 25(4):365-369.
Abstract:The settlement scheme of information management and assistant decision-making system in computer for earthquake precaution and decreasing disaster is introduced from its construction goal, system function, devising principles, software structure design, etc.. By using the technology of GIS, the system fulfilles the function of administrating basic information in GIS. Through further exploitation on the GIS platform, programming with other types of program language, and integrating its analytical functions in space and net with mathematics models in other subjects, the quick earthquake disaster prospect and assistant decision-making functions of the system are realized.
MAO Juan , XING Xi-chun , SHAO Hui-cheng , WANG Jun-ru
2003, 25(4):370-373.
Abstract:Bases on relative frequency of small earthquakes, the seismic information of Jingyang earthquake clusters is obtained and the characters of the clusters are analized. Using correlative analysis method the relationship among the earthquake clusters, the water storage in Fengcun reservoir and the tectonic activity of Kouzhen-Guanshan fault in Jingyang reg ion is discussed. The result shows that the earthquake clusters in Jingyang region are tectonic earthquakes, controlled by regional stress field, and have no relation with Fengcun reservoir.
2003, 25(4):374-379.
Abstract:Adopting the same method used in the study on Yongdeng earthquake[1],the temporal evolution characteristics of shear wave splitting and the geo electrical anisotropy of crust media during the preparation and occurrence of Tianzhu-Gulang MS5.4 earthquake on June first, 1996 are studied.The results show that before the earthquake both the geo electrical axis of ρxy and the polarization of fast S wave rotated from northwest to northeast until occurrence of the earthquake,its source mechanism solution indicats that the P axis direction is in N 50°E. So the three directions are generally the same.On the other hand,the geo-electrical station is coincidently on the seismogenic fault, the variations of apparent resistivity of various frequencies are all evident while the variation of ρxy component is greater than ρxy component contrary to that of Yongdeng earthquake. But due to scarce of collected seismic data the accumulation process of stress is not demonstrated by the time delay between the two split S waves. The other reason for the analyzed result of time delay maybe is the influence of stress adjustment after Yongdeng earthquake on the stress preparation of Tianzhu-Gulang earthquake (the distance between two events is about 120 km).
Sopyright:China Earthquake Engineering Journal