ALBERT

Description: We provide a preliminary report on seismicity before and after the 2023 M7.8 and M7.5 earthquake sequence. One feature for seismicity during 2013-2022 was the 2020 M6.8 earthquake (data from KOERI-RETMC, in Bogazici University). Aftershocks since the M6.8 earthquake suggest that the south end of the M6.8 rupture was close to the north end of the M7.8 rupture. Another feature is a seismic swarm on and around the fault segment, from which the M7.8 rupture was initiated. On this segment, an area of large slip (~1.3 m) was overlapped with this swarm. Since late 2022, this swarm was activated, with a clear decrease in the Gutenberg-Richter b-value to b=0.7~0.8, indicative of an increase in stress. In-depth analyses to verify whether the b-value in the large-slip area pronouncedly decreased preceding its occurrence need to be performed, as in the case for the 2011 M9 Tohoku-oki earthquake in Japan (Nanjo et al., 2011). Comparing with the stress imparted by the M7.8 and M7.5 earthquakes (Toda et al., 2011, 2023), we noted the lack of post-M7.5-quake seismicity at the zone of increase in stress beyond the north end of the M7.8 rupture and that this area lacking in seismicity closely matched to the area of the M6.8 rupture. Future activation that extends to the north on the East Anatolian Fault is unlikely. We will tackle the question whether parts of this fault farther to the north, beyond the M6.8 rupture area, and next to the south of the M7.8 rupture area, may show future activation.

Description: EMSEV's first chairperson, Professor Seiya Uyeda passed away on January 19, 2023, at the age of 93. Electromagnetic monitoring of active faults and volcanoes was driven by hopes of predicting earthquakes and eruptions in the 1970s to the 1990s. Groups from many countries across the world installed instruments and the newly obtained results were presented at many meetings (IUGG, IASPEI, IAGA, IAVCEI, AGU, etc.). These new efforts also led to many lively discussions by groups of researchers on the future formation of an Electromagnetic Studies Working Group to bring together isolated researchers located in many different countries throughout the World. Prof. Seiya Uyeda was one of the most active leaders in this field. The discussion started anew during the 1999 International IUGG GA in Birmingham (UK). This time, Prof. Uyeda’s breakthrough concept was to build a joint Inter-Association (IAGA, IASPEI, and IAVCEI) Working Group to link these isolated scientific groups for developing interconnected field research. Finally, the recommendations were submitted to the IUGG Executive Committee to form an inter-association Working Group focused on a common understanding of the physical processes related to earthquake ruptures and volcano eruptions. Thus, the EMSEV (Electromagnetic Studies of Earthquakes and Volcanoes) Working Group was born. Since then, EMSEV has continued to be active, holding its own general meeting every two years and contributing to the development of electromagnetic research. In the presentation, we would like to praise Professor Uyeda's achievements and introduce the role that EMSEV has played in this field.

Description: As is well known, the last eruption of Mt. Fuji was the Hoei eruption in 1707, and there has been no eruption for more than 300 years. It is common knowledge in volcanology that Mt.Fuji is a very young volcano and it is 100% certain that an eruption will occur in the future. Because of its proximity to the Tokyo metropolitan area, it is believed that an eruption would cause enormous damage to Japan, which has become IT-oriented. In October 2020, our group set up a permanent total magnetism observation point at an altitude of 1400m, which will serve as a reference point for future geomagnetic observations. In evaluating observation data, in order to judge whether it is an artificial change due to a physical change in the position of the sensor (sensor pole tilted due to force majeure, etc.) or a true change in the natural world is very important. Therefore, in the summer of 2022, we conducted geomagnetic preliminary observations from the summit to the vicinity of the 6th station and succeeded in selecting candidate sites for future permanent observation points. In the future, we intend to conduct electromagnetic monitoring of Mt. Fuji as the IUGG-EMSEV project.