An earthquake phenomenon in which fault rupture progresses more slowly than a normal earthquake is called a "slow earthquake".Although it is not accompanied by strong tremors, most of them are adjacent to the area where a large earthquake occurs on the subducting plate interface and share a common mechanism with the large earthquake, suggesting a strong relevance.
The Earthquake Research Institute, the University of Tokyo has reorganized and announced the relationship between slow earthquakes and large earthquakes that occur at the plate boundary based on the characteristics that have been discovered in recent years.He pointed out that it may have the following three roles for a large earthquake.
(XNUMX) Analog (similar phenomenon): Since the activity pattern of slow earthquakes called ETS is similar to that of megathrust earthquakes and occurs frequently, if ETS can be observed and a rule can be found in the mode of occurrence, the mode of occurrence of megathrust earthquakes. May also be understood.
(XNUMX) Stress meter (indicator that reflects the stress state): Slow earthquakes are easily affected by changes in surrounding stress.In addition, from the numerical simulation that the activity changes, such as the interval between slow earthquakes becoming shorter before the occurrence of a large earthquake, it is conceivable that some change will occur in the slow earthquake activity as the occurrence of a large earthquake approaches.
(2011) Stress transfer: Not limited to slow earthquakes, the occurrence of seismic phenomena redistributes stress and affects the surroundings. From the observation results showing the relationship between slow earthquakes and huge earthquakes that have been recently reported, such as the XNUMX Tohoku-oki earthquake, the load of stress on the source area due to the slow earthquake promotes fault destruction in the adjacent large earthquake source area. There is a possibility to support.
The slow earthquake, which was thought to be a peculiar phenomenon at the time of its discovery, has been detected one after another in various parts of the world over the last 20 years, and it has become clear that it is universal as its commonality and diversity become clear. It became.This study suggests that this slow deformation process may be involved in the preparation process for a large earthquake.By continuously monitoring the activity of slow earthquakes and clarifying their activity patterns and causes, it is expected that understanding of the process of occurrence of large earthquakes will be promoted.The results of this research were published in "Science".
