全球强震活动的周期性和对称性

Periodicity and symmetry of global seismicity

对1961—2021年间全球6级以上地震震中分布规律的研究发现,全球地震活动具有一定的周期性,强震活动周期大致为30 a。地震在时空分布上具有平衡特征:空间上,全球6级以上地震在频次和震源深度上分别大致以大西洋洋中脊和赤道对称分布,深源地震的频次较大,且震源深度与频次具有较好的对称性;时间上,大强震发生之前是应力积累阶段,引发板块间或板块内部应力场的增强,当应力场达到最大时爆发大强震,大强震发生之后,应力释放引起板块回弹,又会在一定的时间范围内产生一系列的小地震,直至应力场达到平衡;全球尺度上,地震活动具有周期性及对称性。

The study on the distribution of epicentres of global earthquakes with magnitude≥6 from 1961 to 2021 shows that global seismicity has a certain periodicity,and the period of strong earthquake activity is rough-ly 30 years.Earthquakes have balanced characteristics in the spatial and temporal distribution.Spatially,the frequency and focal depth of global earthquakes with magnitude≥6 are symmetrically distributed in the mid-At-lantic ridge and the equator.The frequency of deep-source earthquakes is higher,and the focal depth and fre-quency have better symmetry.In terms of time,before the occurrence of strong earthquakes,it is the stage of stress accumulation,which leads to the enhancement of interplates or intraplates stress field.When the stress field reaches the maximum,a strong earthquake occurs.After the occurrence of a strong earthquake,the stress release will cause the plate to bounce back,and a series of small earthquakes will take place within a certain time range until the stress field reaches equilibrium.On a global scale,seismicity has periodicity and symme-try.