中国及邻域强震震后变形监测及岩石流变性质研究

Rock Rheology and Observations of Postseismic Deformation Following Strong Earthquakes in China and Its Surrounding Region

大地测量技术观测的震后变形是地壳和地幔岩石对同震应力扰动的变形响应,震后变形的强度及时空演化特征主要受断层面的摩擦性质、下地壳及上地幔岩石的流变参数等控制。震后大地测量被广泛用于研究断层及深部岩石的流变性质及其动力学过程,是对岩石力学实验、冰后回弹等手段探测结果的检验和补充。本文回顾性地总结了中国及邻域中强地震震后变形监测成效,这些震例主要集中在青藏高原内部和边界带。通过对包括昆仑山口西地震、汶川地震和尼泊尔地震在内的发生在青藏高原及周缘的强震震后变形机制、岩石圈流变参数约束等方面的研究,大大提升了对青藏高原不同区域深部岩石流变结构和性质的认识,为研究地震周期变形、地震危险性、青藏高原的形变模式、高原演化动力学提供了观测依据和定量参数。同时,指出进一步约束青藏高原深部岩石流变参数,一方面需要进一步提高西部地区连续GNSS监测能力,另一方面需要与地球物理成像技术进行融合。

The observed transient postseismic deformation represents the response to stress perturbations induced by large earthquakes.The amplitude and spatiotemporal evolution of the postseismic deformation are closely related to frictional properties of the velocity-strengthening region of the fault plane and the viscosity of lower crust and upper mantle.The rheological parameters inferred through modeling the postseismic deformation gain insights to earthquake cycle time scale compared to those values derived from rock-mechanics laboratory experiments and geodetic observations of glacial isostatic adjustment.In this paper,we conduct a brief review on the postseismic geodetic observations following strong earthquakes occurred in China and surrounding regions over the past two decades,in particular the 2001 Kokoxili earthquake,2008 Wenchuan earthquake and 2015 Gorkha earthquake,and summarize the published studies on the postseismic deformation mechanisms and the inferred rheology of the lower crust and upper mantle beneath the margins and interior of the Tibetan Plateau.These progresses shed important lights on earthquake cycle deformation,seismic hazard assessment,tectonic evolution and geodynamics of the Tibetan Plateau.For better understanding the rock rheology of the lower crustal and upper mantle,we suggest to improve the spatial density and temporal resolution of GNSS network in the western China.Moreover,it is very significant to integrate the dynamic modeling of the postseismic deformation with extended geodetic data,such as geophysical surveys from seismic and magnetotelluric imaging.