Xu Changyi et al. -JGR: The impact of earthquakes on the long-term changes in global dynamics parameters

Global dynamic changes, or changes in low -frequency dynamics, usually contain the changes in the low -order gravity field with harmonic coefficient (such as J2), the three -dimensional earth transformation (pole transition and daily long change), etc. The changes of these parameters mainly come from the internal circle The quality exchange of the layer can reveal the dynamics of the solid earth system at different space -time scale and the quality transportation process of the surface fluid.

Traditional concepts believe that long -term changes in global dynamics parameters are led by the Glacier Isostatic Adjustment, and at the end of 20th century, the turning point of the long -term changes in parameters is mainly due to the migration of the surface fluid quality caused by global warming (~ ~ 80%). However, the causes are still uncertain, possible influencing factors include global sector movement, global mantle convection, and even global reservoir water storage behavior recently used for carbon exchange research, and the global earthquake deformation to be discussed next.

Associate Researcher Xu Changyi, an associate researcher of the Institute of Geology and Earth Physics of the Chinese Academy of Sciences, cooperated with Researcher Li Juan to use the principles of planetary rotation dynamics to combine the theory of earthquake errors and the global historical earthquake catalog. Global dynamic parameters have accumulated changes and calculated its contribution to long -term changes in global dynamics parameters.

Based on the observation time sequence of earth dynamics parameters, they first obtained long -term changes in dynamic parameters using the SSA method, and used the MK method to test the trend of long -term changes (whether there was non -linearity). In order to reveal the physical causes of long -term changes, they also calculated the GIA effect they obtained. Studies have found that global dynamic parameters have trended turning in the late 20th century (~ 1998), and the GIA effect cannot fully explain long -term changes (Figure 1).

Figure 1 Global dynamic parameters obtained based on the SSA method change for a long time (red curve). The gray curve represents the observation value, the blue curve represents the impact of the GIA effect

In order to further discuss the contribution of global earthquake deformation, they used the calculation method of the same vibrational parameters based on the theory of spherical earthquake -shaped earthquake -based errors, and the catalog of the global earthquake torque interpretation catalog from 1976 to 2020. (Figure 2 blue curve); Based on the mathematical expression of post -earthquake deformation, the effect of global post -deformation was estimated by selecting reasonable parameters (Figure 2 red curve).

Figure 2 Extremely transitional earth physical stimuli generated by the global earthquake deformation, changes in daily longevity, and the total inertia of J2 and the earth changes. The blue curve in the figure indicates the same shock effect, and the red shadow indicates the same shake+post -vibration effect. Note that the study of the global seismic deformation effect is ignored in this study, and the discussion will be discussed in the later period

The calculation results show that there is a very obvious trend of dynamic parameters generated by the global historical earthquake deformation and accelerate at the end of the 20th century, which is closely related to the global earthquake in the late 20th century. After containing the same earthquake and the post-earthquake effect, the extreme shift generated by the earthquake at a speed of 0.38mas (1MAS = 3.1cm) drifts east of the east; the daily length of the earthquake is -1.42 μs/yr, and the magnitude of the order Although small, it can be seen that the earthquake has been forcing the earth to turn faster. The change rate of the earthquake generated by the earthquake is -5.94 × 10-12/YR, which means that the earthquake forces the earth to become more round. The total inertia of earthquakes generated by the earthquake is -1.00 × 1027kgm2/yr, which means that the earthquake forced the earth to change more densely. Through comparison with observation values, it is found that the global earthquake effect accounts for about 20%or even higher of the long -term changes in global dynamics parameters (Figure 3), and the Earth fluid effects driven by GIA effects and climate change are equivalent to order.

Figure 3 Global dynamic parameters have changed for a long time. The blue curve in the figure represents the long -term changes observation value extracted by the SSA method. The red curve indicates the observation value after deducting the global earthquake deformation. Note that the eastward and north direction of the geo -movement of the earth's physics in the figure is the eastward and north direction of the earth, and the J2

The study detailed the importance of earthquakes in the analysis of the long -term physical cause analysis of the earthquake, and for the viscosity of the observation value of the observation values ​​using dynamic parameters in the future, revealing the dynamic process of the circle, and the long -term Earth's long -term Physical evolution has important reference significance. The study also further emphasizes the impact of earthquake effects when satellite observations such as global water cycle estimation, sea level changes, and GIA effects in the future.

研究成果发表于国际学术期刊JGR-Solid Earth(徐长仪*，李娟.Seismic contributions to secular changes in global geodynamic parameters[J].Journal of Geophysical Research: Solid Earth, 2022, 127, e2022JB024590. DOI:10.1029/2022JB024590 ) Research results are jointly funded by the National Natural Science Foundation of China and key deployment projects.

Beauty editor: Fu Shixu

School pair: Wanpeng

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