The research on relationship between wavelet transform on vertical deformation and moderate earthquakes in hexi region, Gansu Province

In this paper, the possibility of wavelet transform applied to compute the vertical deformation is discussed. Both two dimension plane equation of wavelet transform and B-wavelet based on basic spline function are deduced. According to the equation and B-wavelet, multi-periods vertical deformation data which were measured from 1971 to 1995 in Hexi-Qilian Mountain region, Gansu Province are calculated. The results are: (1) The multi-resolution analysis of wavelet transform can filter the different spatial wavelength in vertical deformation information on different scales effectively and let us to see the heterogeneous in distribution of vertical deformation clearly, therefore, it is an important tool in investigating the relationship between the vertical deformation and the seismicity; (2) The main variation of both the first and second results in wavelet transform mainly takes place along the main faults which explains that the short wave variation of vertical deformation is caused by the faults activities; (3) The wavelet transform of vertical deformation in Hexi-Qilian Mountain area shows that the vertical deformation in southeast parts of Hexi region was larger than that in other parts and there were several moderate earthquakes such as Menyuan M _s=6.4 earthquake in 1986, Jingtai M _s=6.2 earthquake in 1990, Yongdeng M _s=5.8 earthquake in 1995. The vertical deformation in the northwest part of the region was not so large as that in southeast part where ware no strong earthquakes. This paper is supported by the Chinese Joint Seismological Science Foundation.