Kinematic Characteristics of PKIKP and its Derived Phases Based on the IASP91 Earth Model

Since PKIKP is a teleseismic phase with small angle arrived at station, almost vertical to the surface, it is an important phase for establishing the earth’s structure interior, including its derived phases reflected from discontinuity boundaries at the 410 km and 660 km in the upper mantle transitional zone. In this paper, based on the IASP91 Earth velocity model and raytracing technique, the kinematic characteristics of the PKIKP and its derived phases are numerically simulated and analyzed. The results show that the arrivals of the pairs of P4PKIKP and PKIKPP4, pP4PKIKP and pPKIKPP4, P6PKIKP and PKIKPP6, pP6PKIKP and pPKIKPP6 derived from PKIKP are coincided each other, respectively, enhancing the energies for phase identification. The phases pPKIKP, pPKIKPP4, and pPKIKPP6 arrivals are parallel to each other and phases PKIKP, PKIKPP4, and PKIKPP6 arrivals also are parallel to each other for the events with different source depths, and that the time differences between PKIKPP4 and PKIKP, PKIKPP6 and PKIKP always parallel each other and independent of the source depth. When the velocity discontinuity of the upper mantle transitional zone is inclined toward the increasing epicenter distance direction, the travel time of phases PKIKPP4 or PKIKPP6 will increase with distance increasing; Conversely, the travel time will decrease with distance increasing.