Iaffaldano Giampiero, Martin de Blas Juan, Rui Xu, Stamps D Sarah, Bin Zhao
Department of Chemistry, Life Science and Environmental Sustainability, University of Parma, Parma, Italy.
Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark.
Sci Rep. 2024 Jul 16;14(1):16469. doi: 10.1038/s41598-024-67141-3.
Tectonic plate motions drive the earthquake cycle, as they result in the slow accrual and sudden release of energy along plate boundaries. Steadiness of plate motions over the earthquake cycle is a central tenet of the plate tectonics theory and has long been a main pillar in models of earthquake genesis, or of plate-margins seismic potential inferred from slip-deficit estimates. The advent of geodesy in the geosciences and the availability of multi-year-long series of position measurements permit tracking the motions of tectonic plates from before to after the time of significant seismic events that occur along their margins. Here, we present evidence that large earthquakes are capable of modifying the motions of entire microplates. We use high precision Global Navigation Satellite System (GNSS) position time-series covering the periods 2001-2004 and 2014-2017 to demonstrate that, contrary to the tenet above, the South China microplate motion changed after the 2008 7.9 Great Wenchuan earthquake. The GNSS data and associated uncertainties indicate a plate motion slowdown of up to 20% that is beyond the possible impact of data noise and is thus tectonically meaningful. We use quantitative models of torque balance to show that generating this kinematic change requires a force upon the South China microplate compatible with that imparted by the Great Wenchuan earthquake of 2008. The existence of a kinematic signal linked to the earthquake cycle that impacts an entire microplate might offer an additional, novel perspective to assessing the hazards of earthquake-prone tectonic regions.
板块运动驱动着地震周期，因为它们导致沿板块边界的能量缓慢积累和突然释放。板块运动在地震周期内的稳定性是板块构造理论的核心原则，长期以来一直是地震成因模型或从滑动亏损估计推断的板块边缘地震潜力模型的主要支柱。地球科学中大地测量学的出现以及长达数年的位置测量序列的可得性，使得能够追踪板块边界发生重大地震事件前后的板块运动。在此，我们提供证据表明，大地震能够改变整个微板块的运动。我们使用覆盖2001 - 2004年和2014 - 2017年期间的高精度全球导航卫星系统（GNSS）位置时间序列来证明，与上述原则相反，2008年7.9级汶川大地震后华南微板块运动发生了变化。GNSS数据及相关不确定性表明板块运动减缓高达20%，这超出了数据噪声可能产生影响的范围，因此具有构造意义。我们使用扭矩平衡定量模型表明，产生这种运动学变化需要一个作用于华南微板块的力，该力与2008年汶川大地震施加的力相当。与地震周期相关的、影响整个微板块的运动学信号的存在，可能为评估地震多发构造区域的灾害提供一个额外的、新颖的视角。
