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

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）, 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 causes 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 specific tectonic region?　　To answer this question, here, we firstly summarized the spatio-temporal features of global volcanic eruptions based on the Smithsonian Institution Volcano Catalogue 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 folloing.　　Firstly, global volcanic and seismic activities have similar characteristics on the plate scale, and they share the same main tectonic active area, called the Pacific Ring of Fire. However, there may be some certain differences in their genesis 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 old） 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）, 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 character of centennial period since 1800. In the latest centennial cycle, the strong earthquake record is complete, the energy release and cumulated frequency of volcano eruption and strong earthquakes with M≥8 displayed complementarity and quasi-synchronization in temporal evolution, respectively.　　Thirdly, the time series of shallow earthquakes with M≥7 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 in Chinese mainland displayed relatively random distribution in time, and the average magnitude is also relatively high; while after 1955, it showed periodic temporal rhythmic features with obviously alternating 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 activity state reverse of the strong earthquake 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 suppose 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 and shallow earthquakes with M≥7 in Chinese mainland, we deduced that the current seismicity with M≥7 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 geodynamics and analyzing the related earthquake trend.