论文部分内容阅读
理论研究和在兰州台的实际观测都表明,当远震 S 波通过地壳和上地幔速度界面——莫霍界面时,S 波的 Sv成份将产生折射转换波,称之为 Sp 波。Sp 波在台站附近的质点振动方式属于 P 波类型。在一定的距离段上,根据其运动学特征和动力学特征,Sv 波震相可在基式地震仪的垂直分向上辩认出来,是 S 波震相的前驱震相。将 S波震相与 Sp 震相的到时差ΔT 代入公式:H=(ΔT)/K[1/(V_S(K~2-V_S~2δ_S~2)~(1/2))-1/(V_P(K~2-V_p~2δ_p~2)~(1/2))]~(-1)。可求出接收台站附近地壳厚度值 H。本文根据兰州台基式地震仪的21个地震记录,求出了以兰州台为圆心25—50公里环形区域内平均地壳厚度值约为53公里左右。并简要地讨论了 Sp 震相在兰州台的记录特征。初步得出了 Sp 波震在兰州台可观测范围为18°—50°,S 波震相高效率地转换为 Sp 波震相的距离约在32°左右的结论。
Theoretical studies and practical observations at Lanzhou and Taiwan show that the Sv component of the S-wave will produce a refracted wave, which is called the Sp wave, when the S-wave of the teleseismic wave passes through the Moho interface between the crust and the upper mantle velocity. Sp-wave particle vibration near the station belongs to the P-wave type. At a certain distance, according to its kinematics and dynamics, the Sv wave phase can be recognized in the vertical direction of the base seismometer and is the precursor phase of the S-wave phase. The time difference ΔT between the S-wave phase and the Sp-phase is substituted into the equation: H = (ΔT) / K [1 / (V_S (K~2-V_S~2δ_S~2) ~ (1/2)) - 1 / V_P (K ~ 2-V_p ~ 2δ ~ p ~ 2) ~ (1/2))] ~ (-1). The crustal thickness value H near the receiving station can be calculated. Based on 21 seismograms of Lanzhou platform-based seismograph, the average crustal thickness in the region of 25-50 km around Lanzhou station is calculated to be about 53 km. The recording features of Sp seismic phase in Lanzhou station are briefly discussed. It is concluded that the range of Sp wave shock in Lanzhou station is 18 ° -50 °, and the distance between S wave phase and Sp wave phase is about 32 °.