• 固体地球物理及空间物理学（大气、行星、地球动力学、重磁电及地震学、地热学） •

基于全球小口径地震台阵的PcP和PKiKP震相研究

1. 1. 中国科学院地质与地球物理研究所,北京 100029
2. 中国科学院大学,北京 100029
• 收稿日期:2017-12-12 修回日期:2018-09-11 出版日期:2018-10-20 发布日期:2019-01-11
• 作者简介:龙鑫,男,1991年生,硕士研究生,主要从事地核结构方面的研究.
• 基金资助:
国家自然科学基金(41125015);国家自然科学基金(41474040)

Collecting PcP and PKiKP phases pair using global small aperture arrays

LONG Xin1,2(),AI Yin-shuang1

1. 1. Institute of Geology and Geophysics, The Chinese Academy of Sciences, Beijing 100029, China
2. University of Chinese Academy of Sciences, Beijing 100029, China
• Received:2017-12-12 Revised:2018-09-11 Online:2018-10-20 Published:2019-01-11

Abstract:

PcP and PKiKP that reflect from the Earth’s core-mantle boundary and inner-outer core boundary respectively could provide most direct information about physical properties of the two interface in the Earth’s deep interior, for example, density and velocity jumps across the boundary. Such information is critical for us to understand the core-mantle dynamics. Combining PcP and PKiKP to study CMB properties also has advantage over the combination of P and PcP, because ray paths of PcP and PKiKP are much more similar in the upper mantle than those of P and PcP, and effects of upper mantle heterogeneity can be well eliminated. However, due to the small reflection coefficients of PcP and PKiKP, they are usually weaker than other main seismic phases, and it’s often difficult to observe both of them in a single seismograph. Especially for PKiKP, its amplitude is often close to noise level, and stacking techniques are usually required to identify the signal. During recent few decades, the CMB and ICB have been found not simple, and many seismic features related to them has been detected. For example, topography variation and strong heterogeneity near the boundary (mushy zone near the ICB and ultra-low velocity zone above the CMB). Short period PcP and PKiKP are very sensitive to those structure, and can provide good resolution for them. In this study, data of the two phases from global small aperture array are collected, and the global observability of the two phases are compared and analyzed. Phase-Weighted-Stacking (PWS) technique is used to identify the weak PKiKP signal. The small aperture array (inter-station distance of only few kilometers) significantly improves the reliability of the observation, and due to multi-station data of the array, the uncertainties of observation, for example, PKiKP/PcP amplitude ratio could be better estimated. After summarizing previous works, this study also discusses potential prospect of using this phases pair to study CMB and ICB structure, and proposes several applications (e.g., ULVZ, CMB topography and temporary change of ICB).

Key words: CMB, ICB, PcP, PKiKP, small aperture array