LIU Xu , ZHU Yan-qing , TONG Yu-xia
2003, 25(2):97-102.
Abstract:On the base of the data of Sheshan seismic testing array in Shanghai, the features of frequency and amplitude of noise, near event and far event are studied. Some factors affecting correlation among the records of substations in the array are discussed. With the distance between substations getting longer, the co rrelation tend to be smaller; with the distance fixed, the correlation depends on single frequency, epicentral distance (angle of incidence), and the noise vibration. Wiener single-channel frequency filters are not best to use in filtering original data for beam-form. The filters would be designed not only to depress noise but also to keep the well correlated signals in order to beam-form better.
2003, 25(2):103-111.
Abstract:Combining Projection Pursuit(PP)and high-dimensional time series analysis, the synthetic earthquake prediction model of high-dimensional PP time series is built. Selecting Qilian mountain region as research object, its short-term prediction model of the maximum magnitude within three months is made. The qualified rate of prediction test is more than 80%(Prediction error ≤ 0.5 or ≤ 10%). In this paper, it is considered that the model with certain magnitude threshold (MS ≥ 4.0)is better accordding to the real cases. It is available for the model to increase parameters, dimensions, change prediction periods, and generalize to prediction in other fields.
2003, 25(2):112-118.
Abstract:Basic features of the earth deformation field, especially the convex/concave area, in East China during 1987~1990 and relationship among distributions of deformation field,crustal movements seismic belt and epicenters of middle-strong earthquakes are discussed, then some typical cases are analyzed. The results show that the convex/concave area tends to be centered at the region with intense vertical movement. Earthquakes prefer occurring at the copulae between convex and concave areas, which are also the areas with strongest horizontal shear stress. Some information of strong earthquake in Taiwan can be reflected in deformation fields in Fujian and Guangdong provinces. Enhancement or mergence of two or more convex areas may play an important role in triggering occurrence of strong earthquake.
LIU Xiao-feng , YUAN Dao-yang , LIU Bai-chi
2003, 25(2):119-124,142.
Abstract:According to the longitudinal profiles of river terraces of Yellow River and its branch rivers in Lanzhou and adjacent region, the deformation characteristics of river terraces which cross active faults are studied. The extents and rates of tectonic ascent in Lanzhou and adjacent region are confirmed with the grow th and deformation characteristics of the river terraces at positions where the Yellow River terraces cross Xinglong-Maxian mountain fault and Haiyuan Fault, and the Zhuanglang River terraces cross a NWW branch fault of Zhuanglanghe fault.
2003, 25(2):125-130.
Abstract:On the basis of statistical distribution and information entropy theory, information entropy of magnitude (Hm)and information entropy of interval time (Ht)are defined, and their formulas are derived. By means of specio-temporal scanning and calculating, Hm and Ht appear low-value anomaly in 13 years before strong earthquake. Having the better correlation with earthquakes, the Hm and Ht can be used as earthquake forecast indexes for mid or mid -short term.
WANG Lan-wei , ZHAO Jia-liu , XI Ji-lou , WANG Yan-qiong
2003, 25(2):131-135.
Abstract:To be observed on same field in same time, telluric observation is interfered by electric current in measuring the apparent resistivity, and the data are changed to square impulse. In this paper, the method of least square fitting which can be used to eliminate this interference and other random interference in telluric data is discussed. The practically processed result is given also.
YUAN Dao-yang , LIU Xiao-long , LIU Bai-chi , ZHANG Pei-zhen
2003, 25(2):136-142.
Abstract:Reishui-Riyue Mt. active fault zone is a very important NNW oriented right-lateral strike-slip active fault zone which developed in the Chaidam-Qilian Mt. active crustal block, northeastern margin of Qinghai-Tibet Plateau. The activity of the fault causes a series of micro-geomorphologies, such as ridge, valley and terrace, right-lateral offseted and forms fault cliff and fault scarp et al. vertical offset micro-geomorphology. In this paper, the palaeo-earthquake events on the fault are studied. Combining the trench profiles and fault scarp measurement, two palaso-earthquake events are determined, which occured in 6 280 ±120 a B. P. and 2 220 ±360 a B. P., the recurrence interval is about 4 000 a.
ZHANG Si-xin , JIANG Zai-sen , WANG Shang-xu
2003, 25(2):143-148.
Abstract:By calculating and analysing the regional leveling measurement record in near 30 years in Chinese north-south seismic belt and eastern Qinghai-Xizang block, the corresponding relation between crust movement and seismic activity is discovered. During crustal movement represents strong inheritance motion, seismicity is weaker; when inherited movement is abated or represents counter-inheritance motion, seismicity is stronger. The transposition of strengthening and weakening of seismicity is obviously delayed to one of crustal movement, and both activities are periodic and fluctuated. Nowadays crustal movement is enhanced inheritance motion after running to valley, so seismic activity will possibly keep situation and not be enhanced in some future years in Chinese no rth-south seismic belt.
2003, 25(2):149-154.
Abstract:Seismic converted wave is one of methods of explorating earth crust and upper mantle. In this paper, two measuring lines nearly vertical each other in Liaoning province are selected, and the data from relative stations are collected and explained with the method of seismic converted wave. So significant information of deep crustal structure is gotten.
ZHOU M in-du , GUO Zeng-jian , XU Zhong-qiu , FAN Bin
2003, 25(2):155-157,165.
Abstract:The origin times of 7 medium-strong earthquakes in middle-eastern section of Qilian mountain seismic zone in last 20 years are analysed.The result shows that:the earthquakes basically occur about solar term s, and in the first or last ten days of a month; the air temperature on epicenter area is colder before and after earthquake; the origin times are coincident with the peak year or the valley year of solar activity.
LI Yong-li , CAI Jing-guan , LIU Li-fang , ZHANG Jun-wei
2003, 25(2):158-165.
Abstract:By tracing down anomalies of seismological parameters before Shidian MS5 earthquake swarm occurred in 2001, the evolution process of preparation and occurrence of moderate earthquakes for mid short and short imminent terms are studied. The result shows:on the background of anomalies of seismicity parameters including b-value, regulatory ratio of small earthquakes and wave velocity ratio as well as the regular migration of moderate earthquakes for middle term in Yunnan province,some mid short term anomalies such as frequency, b-value and strain acceleration in seismogenic zone of western Yunnan appear.Mainwhile some short imminent term anomalies such as continuous frequency increase of earthquakes with ML ≥ 3.0 and ML ≥ 4.0, anomaly of daily frequency of earthquakes with ML ≥ 3.0 and notable quiescence of earthquakes with ML ≥ 3.0 and ML ≥ 4.0 also appear in Yunnan province. Especially the anomaly quiescence of earthquakes with ML ≥ 3.0 and ML ≥ 4.0 gives obvious mark of imminent information. A preliminary discussion on how to distinguish a single earthquake during the continuous occurrence of moderate earthquakes is made.
2003, 25(2):166-169,174.
Abstract:The character of dynamic variation of stress field in north part of Chinese north-south seismic belt is analysed, and com paring with data of some earthquake precursor observations, the relationship between the variation of stress field and seismicity is studied. At last the mechanism of the variation and the possibility of using it to protect earthquake are discussed.
ZHANG Yuan-sheng , LI Qing-he , LIU Yao-wei , ZHOU Min-du
2003, 25(2):170-174.
Abstract:GABW IT is a software of inversion for 3D crustal velocity structure using seismic body travel time data and genetic algorithms. The main function and technological character of the seismic tomography software are introduced. GABWIT has a good desktop, perfect function, and is easy for operation and popularity.
2003, 25(2):175-178,185.
Abstract:In this paper, Sichuan-Qinghai crustal block and their movement towards southeast were further proved, based on some new evidences provided by recent studies on seismicity, mechanism of earthquake focus, active fault and crustal structure.
ZHU Yi-qing , WNG Shuang-xu , CHENG Hong-bin , CHEN Bing
2003, 25(2):179-182.
Abstract:The phenomenon of time-space association among the strong earthquakes in Chinese north-south seismic belt since 1970 is analyzed. The magnitude and epicenter of the responsive earthquake after two earthquakes occuring in succession has the charactor of "Golden section", and it is closely related with seismic tectonics.
2003, 25(2):183-185.
Abstract:The data conversion form and design method of conversion program in listing earthquake report cata-logue are analysed. Using the database language, the data conversion program is writtern, so a useful tool software is supplied to listing the earthquake monthly report catalogue and the historical earthquake catalogue.
TANG Yu-xiong , YANG Ji-wu , DONG Bi-xian
2003, 25(2):187-192.
Abstract:By using the author's self-made RS-81-1 TL dating device, the TL dating and microscopic structure analysis on calcite veins in 2 fault shatter belts in Yudong reservoir, Yunnan Prov., China, are done. The result shows that there are 4 groups of calcite veins which form in different time, among them 3 groups have been deformed. F1 fault since 15×104 years and F2 fault since 25×104 years have no evidence of activity. The surface characteristic analysis on quartz coarse-grain indicates the same result with TL dating method.
Sopyright:China Earthquake Engineering Journal