Anomalous SmKS induced by postcritical reflection and refraction at the core-mantle boundary

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2019,（21）
• 页码范围: 1601-1607
• 页数: 7页
• 语种: 英文

摘要

Earth's outer core is generally thought to be a well-mixed liquid consisting mostly of iron and a small amount of lighter elements.Recent seismic studies using SmKS waves show that the top a few hundred kilometers of the outer core possess a P-wave velocity slightly lower than the PREM model,which cannot be explained by self-compression of a chemically homogeneous outer core.We investigated the SmKS waveforms of a deep earthquake occurring beneath South America recorded by a large and dense seismic array in China,and measured the differential arrival times of the SmKS pairs.We found significant wave-form distortion of the SmKS caused by postcritical refraction and reflection at the core-mantle boundary.This waveform distortion can introduce significant bias to the measured differential times,leading to incorrect estimate of P-wave velocity of the outer core.Whether stable stratification is occurring in outer core or not requires further seismic investigations.