Anelasticity of the Crust and Upper Mantle of South America From the Inversion of Observed Surface Wave Attenuation

Fundamental-mode Rayleigh and Love waves generated by several earthquakes situated along great-circle paths between pairs of seismograph stations have been analysed to obtain coefficients of attenuation, group velocities, phase velocities, and specific quality factors in the period range 18–80s in two regions of the South American continent. One set of paths crosses the shield region which lies on the eastern coast and another set traverses the mountainous region inland. the average attenuation coefficient values are clearly higher in the tectonically active western region throughout the entire period range than in the eastern or shield region.
Inversion of the attenuation data yielded shear wave internal friction ( Q ^-1_β) models as a function of depth in the crust and upper mantle in both regions. A low- Q zone below the lithosphere is prominent in both regions. the results show that substantial variations of Q _β occur in the two regions of South America. the Q_β values were found to be inversely related to the heat flow values or to the temperature.     

表土结皮发育过程及其侵蚀响应研究进展

表土结皮是降雨后某些土壤表面普遍存在的现象，它是在降雨与土壤的相互作用下发育的；本文在综览大量文献的基础上，得出表土结皮研究还存在着很多有待深入的领域。一方面，由于影响降雨、土壤的因子复杂多变，因此表土结皮本身的形成过程很复杂，研究者的结论也有所不同。另一方面，表土结皮作为一种特殊的下垫面，影响坡面侵蚀的各子过程，但是影响机理还不清楚。表土结皮对坡面侵蚀过程的影响研究已经取得了一些定性方面的进展，但为了完善坡面侵蚀物理模型和达到准确的预报预测，定量研究还有待进一步深入和细化。