The influences of large earthquake signals on the recovery of surface waves from ambient noise cross-correlation functions

Ambient noise tomography(ANT)has been widely used to image crust and upmost mantle structures.ANT assumes that sources of ambient noise are diffuse and evenly distributed in space and the energy of different modes is equipartitioned.At present,the sources of the primary and the secondary microseisms are well studied,but there are only a few on the studies of long-period ambient noise sources.In this study,we study the effects of large earthquake signals on the recovery of surface waves from seismic ambient noise data recorded by seismic stations from the US permanent networks and Global Seismographic Network(GSN).Our results show that large earthquake signals play an important role on the recovery of long-period surface waves from ambient noise cross-correlation functions.Our results are consistent with previous studies that suggest the contribution of earthquake signals to the recovery of surface waves from cross-correlations of ambient noise is dominant at periods larger than 20–40 s.

超声造影与MRI诊断肝泡型包虫病病灶生物学活性的一致性分析

目的探讨超声造影(CEUS)与MRI诊断肝泡型包虫病(HAE)病灶生物学活性的一致性。方法本研究对象为2019年10月至2020年12月青海大学附属医院收治的47例HAE患者。患者均签署知情同意书,符合医学伦理学规定。其中男17例,女30例;平均年龄(36±2)岁。患者均在1周内分别行CEUS和MRI检查,分析其图像特点,评价病灶的生物学活性。采用Kappa检验分析CEUS增强模式与MRI小囊泡样结构对HAE病灶生物学活性诊断的一致性。结果47例患者CEUS共检查出77个病灶,62个病灶显示边缘增强,其中高增强19个,等增强15个,低增强28个。MRI按照矫正后Kodama分型,1型1个,2型20个,3型37个,4型17个,5型2个。MRI检出53个小囊泡样结构病灶具有生物学活性,CEUS检出62个,两种检查方式的一致性较好(κ=0.696,P<0.001)。结论CEUS与MRI诊断HAE病灶的生物学活性具有较好的一致性。与MRI相比,CEUS具有方便、易操作、经济等优势,可有效评估HAE病灶的生物学活性,随访HAE的病情变化。