In the moment-ratio imaging algorithm,which is based on the theory of healing of a wound,the energy of each strong earthquake is distributed around the epicenter according to certain rules,and the features of the Mo-ment-ratio value R are analyzed as the space and time change,so that the relationships between the moment-ration value R and strong earthquakes can be found. In the present paper,regions divided,hypocenter depths and events completed magnitude analyses were carried out in the Chinese catalogue. By applying the moment-ratio imaging algorithm in which the parameters are adjusted,the processes of anomaly evolution which correspond to the epi-center and the surrounding value R before earthquakes of M≥7.0 since 1966 in different areas of China were ana-lyzed. It was found that the range area and imminent time of a coming earthquake could be confirmed quantita-tively by analyzing the abnormal temporal and spatial variation of the value R. The results showed that the tempo-ral and spatial variation of the value R could quantitatively reflect the temporal and spatial factors of a coming strong earthquake as well as the rule of medium rupture.
In Capital Circle area, there are three groups of repeated gravity measurements observed by different institutes using different instruments or methods. The simultaneous adjustment of absolute and relative measurements and the elimination of systematic error among the relative measurements have been carried out in this paper. Thus an unified temporal gravity change system with absolute reference has been established. On the basis of this, the crustal subsidence effect on gravity, which belongs to non-tectonic factor, is analyzed and the station displacement corrections are carried out, so that the long-wave disturbance is eliminated. So far our following aims are realized: the advantages of the absolute and relative measurement methods are complementary to each other; the contradic- tion and environment disturbance are eliminated; the amounts of information are enlarged; the sampling interval of time domain is compressed. In a word, the ability of identifying the tectonic activity process is enhanced. The re- sults show that: there are systematic errors between the two groups of relative measurements and within the data of 10 campaigns ; the uneven local crustal subsidence in the southeast of the study area results in a linear rise of grav- ity value at 10 stations; they can be corrected by the regression analysis. The maps of revised temporal gravity change can obviously and integrally reflect the MS=5.0 earthquake in Guye on October 6, 1995.
Coseismic water level changes which may have been induced by the Wenchuan MS8.0 earthquake and its 15 larger aftershocks(MS≥5.4) have been observed at Tangshan well.We analyze the correlation between coseismic parameters(maximum amplitude, duration, coseismic step and the time when the coseismic reach its maximum amplitude) and earth-quake parameters(magnitude, well-epicenter distance and depth), and then compare the time when the coseismic oscillation reaches its maximum amplitude with the seismogram from Douhe seismic station which is about 16.3 km away from Tangshan well.The analysis indicates that magnitude is the main factor influencing the induced coseismic water level changes, and that the well-epicenter distance and depth have less influence.MS magnitude has the strongest correlation with the co-seismic water level changes comparing to MW and ML magnitudes.There exists strong correlation between the maximum amplitude, step size and the oscillation duration.The water level oscillation and step are both caused by dynamic strain sourcing from seismic waves.Most of the times when the oscillations reach their maximum amplitudes are between S and Rayleigh waves.The coseismic water level changes are due to the co-effect of seismic waves and hydro-geological environments.
Baojun YinLi MaHuizhong ChenJianping HuangChaojun ZhangWuxing Wang
