全球火山活动时空分布特征及其对强震活动趋势的指示

Spatio-temporal distribution characteristics of the worldwide volcano activity and their implication to the strong earthquake trends

基于史密森学会火山目录分析了全球火山活动的时空特征,并结合中国地震台网目录讨论了火山活动对全球和中国大陆强震活动趋势的指示意义。结果显示:①全球火山活动表现出较为显著的百年周期特征,且百年周期内火山活动和M≥8.0大震之间存在着频次准同步和能量互补现象;②中国大陆1955年前后强震活动状态的变化可能与同期全球火山活动状态变化密切相关,且二者可能受控于百年周期内地球内部能量积累与释放的状态变化;③2022年汤加火山的剧烈喷发意味着地球内部能量仍在持续释放。结合全球M8地震和中国大陆M7浅源地震的活动特征,认为当前及未来一段时间全球及中国大陆的大震活动状态可能与二十世纪上半叶相似。

Identical with earthquakes,volcanic eruptions also play a role of energy release from the Earth’s interior.And the volcanic eruption intensity can be measured by volcanic explosivity index(VEI for short),which is determined by the volume of the eruption material and the height of the volcanic ash column.On January 15,2022,a volcano erupted violently in Tonga in the South Pacific Ocean with the eruption intensity as high as VEI=5.And the energy release possibly exceed 58 Mt TNT,almost six times as much as the energy released by the great Wenchuan earthquake in 2008.The extremely energy release has attracted widespread attention from international scientists and has a significant impact on the global atmospheric environment and climate change.However,as a way of energy releasing of the Earth’s interior,whether the violent eruption of the Tonga volcano was related to the state change of strong earthquake trend worldwide or in a specific tectonic region?In other words,can the extreme eruption of the Tonga volcano provide some clues or indications for the analyses of strong earthquake trend worldwide or in a specific tectonic region?To answer this question,here,we firstly summarized the spatio-temporal features of global volcanic eruptions based on the the volcano catalogue from Smithsonian Institution and reviewed the characteristics of strong earthquake activities in the whole world and Chinese mainland on the basis of earthquake catalogue from China Earthquake Network.And then,we analyzed the possible indications of volcanic activity to the trends of global and Chinese mainland strong earthquakes in the viewpoint of the seismicity analysis.What is more,the possible change in strong earthquake trends of the whole world and Chinese mainland after the Tonga volcanic eruption is also discussed.The results are as following.Firstly,global volcanic and seismic activities have similar characteristics on the plate scale,and they share the same main active tectonic area,called the Pacific Ring of Fire.However,there may be some certain differences in their tectonic environment.Both the volcanic eruption and strong earthquakes are more likely to occur at the boundary of the youngest(0−50 million years)plates,such as Mexico,Chile-Peru and Vanuatu,or the boundary of the oldest(more than 90 million years)plates,such as Japan and New Zealand.But,instead,the volcanic eruption and strong earthquake activity displayed opposite state in some specific tectonic regions with middle-aged(50−90 million years)plate,such as the western section of Alaska subduction and the northern section of Sumatra subduction,where large earthquakes are active but volcanism is weak.Secondly,similar to the Gutenberg-Richter law in seismic activity,the volcanic eruption magnitude and accumulated frequency also satisfied power-law distribution.Moreover,the volcanic eruption also displayed periodic activity characteristics in time and intensity.The global volcanic activity can be divided into two visible characteristics of centennial period since 1800.In the latest centennial cycle,the strong earthquake records are complete,the energy release and cumulated frequency of volcano eruption and strong earthquakes with M≥8.0 displayed complementarity and quasi-synchronization in temporal evolution,respectively.Thirdly,the time series of shallow earthquakes with M≥7.0 in Chinese mainland since 1900 shows that the year 1955 is a significant time-point of strong earthquake activity in Chinese mainland.Before 1955,the strong shallow earthquake activity with M≥7.0 in Chi-nese mainland displayed relatively random distribution in time,and the average magnitude is also relatively high;while after 1955,it showed temporal rhythmic features with obviously al-ternating between calm and active periods,and the average magnitude is lower than that before 1955.Similarly,global volcanism around 1955 also showed clearly segmented characteristics,which are mainly reflected in three aspects:volcanic activity intensity,frequency and energy release.Our analyses suggest that the reverse of strong earthquake activity state before and after 1955 should be related to the contemporaneous increasing of the global volcanic activity.Both of them could be attributed to the change in energy release state of the earth interior in its centennial activity period.Finally,based on the analysis of global strong earthquake activity,we deduce that the violent eruption of the Tonga volcano may indicate that the energy release of the Earth’s interior is still ongoing.In combination with the seismicity of global earthquakes with M≥8.0 and shal-low earthquakes with M≥7.0 in Chinese mainland,we deduced that the current seismicity with M≥7.0 in Chinese mainland may be similar to that in the first half of the 20th century.Our works in this paper could provide a reference for understanding the seismological geo-dynamics and analyzing the related earthquake trend.