重力位能同震变化及其构造意义——以青藏高原地区为例

地震除了以地震波的形式释放能量之外,地震还会使地球产生永久变形,该变形将使重力位能产生变化.研究表明,地壳的重力位能的同震变化能够很好地揭示构造活动的拉张或挤压状态.本文首先基于球对称、非自转、弹性和各向同性(SNREI)地球的点源位错理论,提出了一种有效的计算重力位能的同震变化的方法,该方法不仅适用于剪切型地震,而且适用于拉张型地震;然后研究了青藏高原地区在1976-2013年间发生的地震对地壳重力位能的同震变化的影响.结果表明,青藏高原中部和西部的地震使得整个地壳的位能减小,而东部的地震使位能增大;位能的减小和增大对应了该地区构造活动的拉张和挤压状态;并且1999-2013年期间较1976-1998年期间地震对地壳重力位能的影响加剧.

Co-seismic change of gravitational potential energy and its tectonic implications:A case study of the Tibetan plateau

Earthquakes not only release seismic-wave energy, which decays eventually, but also give rise to permanent deformation in the Earth. This permanent deformation causes change of gravitational potential energy (GPE). Previous studies showed that the GPE change is a good indicator of extensional and compressional tectonics. In this work, we first proposed an effective method to compute co-seismic GPE change for a SNREI (spherically symmetric non-rotational elastic isotropic) Earth according to the point dislocation theory. This method is applicable to both shear and tensile earthquakes. We then applied this method to compute the contributions of the earthquakes occurred in the Tibetan plateau area from 1976 to 2013 to crustal GPE change. The results show that the earthquakes in the central and western Tibetan plateau caused crustal GPE to decrease while those in the eastern part caused it to increase, which correspond to extensional and compressional tectonics, respectively, in this area. Furthermore, the impact of the earthquakes from 1999 to 2013 was greater than that of the events from 1976 to 1998.