A research group led by graduate student Yusuke Kakiuchi and professor Takeshi Tsuji at the University of Tokyo Graduate School has developed a method to monitor information deep in the earth's crust, such as volcanic magma chambers, with high temporal resolution. This revealed that during the 2011 off the Pacific coast of Tohoku Earthquake, water pressure rose directly beneath Mt. Fuji and Hakone, and that water pressure in volcanic areas is difficult to return to pre-earthquake levels.
Volcanic activity increases after an earthquake. This is thought to be caused by the fact that even if an earthquake occurs far away, the shaking is transmitted far away, stimulating the volcano's magma chamber and causing gas to bubble. However, it has been difficult to capture phenomena deep in the earth's crust with high spatiotemporal resolution, making it difficult to discuss the relationship between earthquakes and volcanic activity.
Using a method called seismic interferometry to detect the earth's "tremors," which cannot be felt by humans, it is possible to detect temporal changes in the velocity of waves (elastic wave velocity) traveling deep within the earth's crust. The research group succeeded in monitoring the Earth's crust by increasing the temporal resolution from several days to one day by using information on all vibration components from seismometers and introducing data analysis technology.
As a result, it was found that during the Tohoku Pacific Coast Earthquake, a large change in elastic wave velocity of approximately 0.2% occurred directly beneath Mt. Fuji and Hakone Volcano, and that elastic wave velocity in volcanic areas is difficult to return to its pre-earthquake state. Do you get it. This revealed that gas and fluid pressures increased in volcanic areas such as Mt. Fuji and Hakone. It is said that the pressure of the fluid increases even before a volcanic eruption.
The information obtained from this monitoring (changes in wave speed) captures the depths of the earth's crust, and if it is integrated with previous monitoring results obtained at the surface (surface deformation obtained by GPS, etc.), accurate monitoring of volcanic activity will become possible. It is said that
