Using 3-C uphole survey technique to survey P-wave and S-wave velocity on surface.
Li Gui-hua and Zhu Guang-ming. Department of Geology and Environmental Engineering, Xi'an University of Science and Technology, Xi'an City, 710054, China
In order to provide accurate model of near-surface P- and S-wave velocity and thickness, in the continent scientific drilling sites in N area of the northeast of Jiangsu Province, China, the three different surveying methods of 3-C uphole survey for near-surface surveying were used: ①shooting by dynamite on surface and receiving by 3-C geo-phones in the hole; ②shooting by using hammer on the surface to hammer at sleeper laterally and receiving by 3-C geophones in the hole; ③shooting by dynamite in the hole and receiving simultaneously by T geophone, 3-C geophones and VSP wavelet 3-C geophones on surface. The paper described in detail the acquisition, equipment and processing methods of 3-C uphole surveying data in these three different surveying methods and gained the following knowledge: the reliable first breaks of P-wave can be picked up in vertical components shooting by dynamite on the surface, but the first breaks of S-wave are difficult to be accurately picked up by using horizontal components; the S/N ratio in SH-wave data of horizontal components shooting by hammer on the surface hammering at sleeper laterally is higher, but S/N ratio of the first breaks of P-wave in vertical components is not high; the reliable first breaks of P-wave can be picked up in vertical components shooting in the hole and receiving on the surface, the S-wave arrivals can be observed in horizontal components, but there are multiple group of events before and after S-wave arrivals that makes difficult to recognize true S-wave, nevertheless, using waveform feature or dynamic feature in horizontal components can i-dentify the depth position of layered S-wave velocity. The accurate near-surface information, the P-and S-wave static corrections needs were gained by interpretation of uphole surveying data in the work area. At meantime, some suggestions about equipments and surveying methods of next 3-C uphole survey technique are also presented in the paper.