1999, 21(4):345-349.
Abstract:In nature there are many phenomena having the temporal characteristics of multipled nine days, such as the period of nine day in the Earth's rotation, in the solar and lunar tidal forces, in geomagnetic activity, in atmospheric rhythm and so on. In the case, strong earthquake occurrence time may be modulated and triggered by the phenomena, so earthquake occurrence in some degree is characterized by the temporal regularity of multipled nine days.It is valuable for impending earthquake prediction.Based on occurrence dates of strong earthquakes in Gansu Province and neighbour regions the objectivity of multipled nine days have been demonstrated.
CHANG Ke-gui , GAO Li-xin , ZHANG Jian-ye , CAO Jing-quan
1999, 21(4):350-355.
Abstract:The variation characteristics of the load-unload response ratio with time before the Bao-tou MS6.4 earthquake are studied by using the load-unload response ratio theory. The result showed that there is obvious anomaly before the earthquake. The influence factors on the anomaly contained not only time, amplitude, selected region and lower limit magnitude, but also seismotectonics and structures controlling earthquakes. For the relationship between anomaly and earthquake, there will be an earthquake when the ascendant anomaly has arisen, had a turn in the course of events and returned to normal. The time of anomaly is sustained from one year to four years.
ZHANG Zhao-dong , LIU Qing-guo , WEI Huan , GENG Jie , WANG Zhong-min
1999, 21(4):356-362.
Abstract:The theory and method of the loading and unloading response ratio to the earth tide have been quoted in data calculation of tides of the gruondwater level.The feasibility for calculating the loading and unloading response ratio by means of the observation data of the gruondwater level is proved, and the calculation method has been showed.The loading and unloading response ratio of the groundwater level to the earth tide in the North China during the last 20 years has been calculated by this method, and the variation of loading and unloading response ratio of groundwater level to earth tides before and after the Datong MS6.1 earthquake in 1989 has been analyzed.Increasing anomaly variation of the loading and unloading response ratio of most of the well levels to the earth tides appeared from 6 to 12 monthes before the earthquake.
CAI Jing-guan , ZHANG Xi-ling , LI Yong-li
1999, 21(4):363-369.
Abstract:The pattern of vp/vs ratio anomaly for M ≥ 6.5 earthquakes in the fourth activity period in Yunnan area was dynamically traced, it clearly showed the difference in south and north. The Lancang Gengma M 7.6 and M 7.2 earthquakes on November 6, 1988 and the Puer M 6.3 earthquake on January 27, 1993 in southwest Yunnan occurred in low vp/vs ratio anomaly area, the China Burma border M 6.7 and M 6.8 earthquakes on April 23, 1992 and the west Menglian M 7.3 earthquake on July 12, 1995 occurred along the margin of this area, while the Lijiang M 7.0 earthquake on February 3, 1996, the Ninglang M 6.7 and M 6.4 earthquakes on November 7 and December 13, 1976 and the Wuding M 6.5 earthquake on October 24, 1995 occurred in high vp/vs ratio anomaly region.
Before strong earthquakes, the north south difference between near shock magnitude M L and continued time magnitude MD demonstrated further the difference of vp/vs ratio.
XIANG Hong-fa , Yasutaka Ikeda , ZHANG Wan-xia , HE Hong-lin
1999, 21(4):370-377.
Abstract:By investigating, measuring and dating the offset streams in several typical segments in Shikoku, Japan, it is achieved that average offset rate of the Median Tectonic Line is 6.1 mm/yr.since the late Pleistocene.The facts that there is high slip rate, but no disastrous earthquake on the Median Tectonic Line in the recent 1 000 years show that it may be mainly in the period of creep movement. The major earthquake rupture in the future may happen in the joint area of the north side of Median Tectonic Line with the NNE-trending, newly-generated fault.
1999, 21(4):378-382.
Abstract:The behaviors of geothermal vortexes before and after strong earthquakes in China in last decades are analysed. The results show that there are clear local features in evolution of geothermal vortexes relating to strong earthquakes in different regions. One of the most important features is the merger of geothermal vortexes.The model of merger of geothermal vortexes is discussed.
HE Kai-ming , MENG Guang-kui , BAN Tie , CUI Li-ming
1999, 21(4):383-388.
Abstract:Based on tri-component measurement of microtremor on different thickness sediment layers in Yinchuan basin, the curves of ratio of horizontal spectrum to vertical spectrum were drawn.These curves show that the frequency value corresponding to maximum peak obviously reflect the sediment layers' thickness. Comparing the frequency value with predominant frequency of some buildings in Yinchuan, it can be concluded that these buildings would be seriously damaged by future earthquakes.
CHEN Wen-bin , LIU Bai-chi , XU Xi-wei , DAI Hua-guang , WANG Feng
1999, 21(4):389-394.
Abstract:Field investigation reveals that the latest time when Yumen fault, western part of Qilian Mountains was active is the end of the late Pleistocene, and that the fault is coincident with other faults around west Jiuquan basin.It is also found that Yumen fault had not simply restricted to dip-slip motion, strike slip motion is indicated. The results suggest that west Jiuquan basin block might have rotated clockwise.
1999, 21(4):395-398,406.
Abstract:The present motion status of the Ordos block is studied by using the relevant result of the‘Wheel and Gate Model’about the mutual action between the northeastern Qinghai-Tibet Plateau and the Ordos block and based on characteristics of seismicity and focal mechanism solutions in recent years. The results show that the Ordos block is still controlled by the strong sinistral compresso-shearing from the northeastern Qinghai-Tibet Plateau. Its tectonic motion is restrained, so the seismicity around the Ordos block has maintained its activity form and level since 1815.
YANG Ma-ling , QU Yan-jun , WANG Hai-tao , WEN He-ping
1999, 21(4):399-406.
Abstract:Based on the M-estimation of normal density ψfunction, a robust regression mathematical model that contains the combination of tendency term and periodic term is set up. The emulation data that contains a few discrete points are calculated by using three methods (least-squares estimation, robust estimation, least-squares estimation after revising the discrete points). It is shown that robust estimation can avoid the evil of least-square method in which the result will be considerably influenced by discrete points, and the mathematical model parameter is closer to the fact. The calculation results of precursor data (tide of the solid earth and underground gas) also show that this mathematical model can avoid the disturbance of the discrete points and more truly reflect the tendency of precursor data. The method will become a powerful tool for analysing the tendency of precursor data.
ZHANG Shi-yin , LI Yu-min , LI Bo-hui
1999, 21(4):407-410,416.
Abstract:The anomaly characteristics of well water level at Zhuangshi, Ningbo before three MS >5. 0 earthquakes in South Yellow Sea is summarized and analysed. The results show that there are more than half a year trend anomaly and variation of annual regular before MS >5. 0 earthquake in most cases and short-imminent term precursors appear one mo nth or two months before the earthquake, such as variation of water level solid tide, increase of wave amplitude of date tide range and leapfrog etc. The analysis has played an important role in earthquake prediction practice of Zhejiang Province.
ZHANG Chao-jun , ZHAO Meng-sheng , WANG Bin
1999, 21(4):412-416.
Abstract:By researching the spatial relationship of the Baotou MS6.4 mainshock, aftershocks and 51 ML ≥ 2.0 foreshocks which occurred in the region of 40°00'~41°10'N, 108°20'~110° 30'from 1992 to the April, 1996, it is show n that the direction of foreshocks distribution is consistent with the principal stress orientation in focal mechanism solution of the Baotou MS6.4 mainshock, their focal depths are in the scope from 9 to 34 kilometers, 78 percent of them occurred beyond the depth of 20 kilometers, the small earthquakes activities made the region from Baotou to Huhhot form a gap. The Baotou MS6.4 earthquake occurred just in the gap. It is considered that the earthquake was brittle fracture, normal and sinistral strike slip.
CHEN Jun-ying , LIN Chang-you , YANG Chang-fu , WANG Shu-ming , LUO Dong-shan , LU Fu-lin
1999, 21(4):417-422.
Abstract:The physical meaning of the apparent resistivity ρzy which is defined by the ratio between magnetic field's components and its phase in the frequency electromagnetic sounding with the electric dipole sources is discussed and the method of estimating the phase by using the data of the apparent resistivities on the basis of dispersion relation is given. It has been proved that the estimated phase values coincide with those calculated by theoretical models. In addition, the ρzy-φzy joint inversion problem is studied and the practical software which has a better effect in the application is developed.
1999, 21(4):423-427.
Abstract:Analysing the law of earthquake disaster of chimneys, it is taken into account that vertical earthquake force acts mainly in destruction of chimneys during an earthquake. A method of calculating vertical earthquake action by impulse way is proposed. By using the method, vertical earthquake action of a reinforced concrete chimney 190 meters high is calculated, and the result is analy-sed. Some problems worthy to be noted in design of chimney are discussed. The calculation of the vertical earthquake action in high-rise construction design is necessary.
1999, 21(4):428-429.
Abstract:The observed helium content data in Liaogu-1 well from 1981 to 1984 have been processed. It has been found that the data of helium content have a clear abnormal change and their anomaly forms are very alike before two near earthquakes (Ningjin MS5.8 in 1981 and Heze MS5.9 in 1983).
QING Mei , PAN Hai-tao , DAI Wei-le
1999, 21(4):430-432.
Abstract:在1976~1983年期间,格陵兰地区共记录到53个地震.所有的地震资料都用检查地震记录图纸的方式进行了复核审查,得到了该地区Pn,Pg,P11(PMP),Sn和Lg波的走时曲线及其视速度,这些结果与加拿大的走时曲线相一致.发现有9个地震的11张地震图上记录到一个附加的i震相.初步研究认为,i震相的存在与震中距、震源深度和地震方向有关,不过此现象尚须进一步研究.
GAO Shu-de , YAN Zheng , KANG Hao-lin , SU Yong-gang
1999, 21(4):433-435.
Abstract:着重探讨武都地电台测区埋设地下光缆后北西道地电阻率测值急剧上升的原因.通过实际观测、理论分析和实验,总结出了这种变化的机制,定量地解释了埋设地下光缆对地电观测的影响,从而为以后判断地电测值变化是干扰还是地震异常提供了依据.
Sopyright:China Earthquake Engineering Journal