Interpretation of S-wave data from Tai’an-Xinzhou DSS profile and its relationship with Xingtai earthquakes

On the basis of S wave information from Tai'an-Xinzhou DSS profile and with reference to the results from P-wave interpretation, the 2-D structures, including S-wave velocity V ^sub s^, ratio γ between V ^sub p^ and V ^sub s^; and Poisson' s ratio σ, are calculated; the structural configuration of the profile is presented and the relevant inferences are drawn from the above results. Upwarping mantle districts (V ^sub s^[asymptotically =]4.30 km/s) and sloping mantle districts (V ^sub s^[asymptotically =]4.50 km/s) of the profile with velocity difference about -4% at the top of upper mantle are divided according to the differences of V ^sub s^, γ and σ in different media and structures, also with reference to the information of their neighbouring regions; the existence of Niujiaqiao-Dongwang high-angle ultra-crustal fault zone is reaffirmed; the properties of low and high velocity blocks (zones) including the crust-mantle transitionalzone and the boudary indicators of North China rift valley are discussed. A comprehensive study is conducted on the relation of the interpretation results with earthquakes. It is concluded that the mantle upwarps, thermal material upwells through the high-angle fault, the primary hypocenter was located at the crust-mantle juncture 30.033.0 km deep, and additional stress excited the M ^sub S^=6.8 and M ^sub S^=7.2 earthquakes at specific locations around 9.0 km below Niujiaqiao-Dongwang, the earthquakes took place around the high-angle ultra-crustal fault and centered in the brittle media and rock strata with low γ and low σ values.[PUBLICATION ABSTRACT]