13:45 〜 14:00
[SCG44-01] Getting started on Science of Slow-to-Fast Earthquakes
キーワード：スロー地震、ファスト地震、研究計画
Science of Slow-to-Fast Earthquake, a Grant-in-Aid for Scientific Research on Innovative Areas (A), started last September. In this project, researchers from various fields such as physics, geology, geophysics, and geochemistry will participate in six planned research subgroups (A01 Physicochemical Processes, A02 Structural Anatomy, A03 International Comparison, B01 New Technology Observation, B02 Information Science, and B03 Model and Forecast), as well as in the publicly offered research subprojects, in order to significantly advance our understanding of slow and fast (ordinary) earthquakes.
Even after 20 years since the discovery of slow earthquakes, new discoveries continue to be made around the world. In recent years, detailed studies of tectonic tremor and SSEs, especially in New Zealand and off the coast of Tohoku, have changed the view that Nankai and Cascades are representative of slow earthquake regions. Slow earthquakes are not uncommon and should be considered as a universal phenomenon that occurs wherever fast earthquakes occur. It is necessary to clarify the boundary between fast and slow earthquakes in the overall seismic phenomenon by using state-of-the-art observations, information science-based analysis methods, and comparative studies of various regions.
Ide et al. (2007) compared seismic moments and durations and identified slow earthquakes as unified ultra-broadband slow earthquakes as opposed to fast earthquakes. There is certainly evidence of broadband slow earthquakes up to about 1000 seconds. However, the occurrence of SSEs without tectonic tremor and the various deformation modes proposed by geology and geophysics suggest that slow earthquakes are not a single physical phenomenon. On the other hand, fast earthquakes always include the interaction between rupture and propagating seismic wave. Since the discovery of slow earthquakes, we may have often regarded earthquakes as normal and slow earthquakes as strange phenomena. However, in fact, among various deformation phenomena, rupture interacting with long-distance propagating waves (fast earthquakes) is the unique process. It is essentially important to find out the material and physical conditions that produce the interaction between rupture and waves.
In addition, forecasting future seismic activity is unavoidable in earthquake research. How does slow earthquakes contribute to the preparation for a huge fast earthquake? A re-examination of seismic activity is underway with the simultaneous occurrence of slow earthquakes in mind. In parallel with the explanation studies using numerical models with differential equations, probabilistic forecast with stochastic processes will also be important. We would like to reach an understanding that will allow us to give more accurate advice on the implications of slow earthquakes in the national earthquake countermeasures.
Even after 20 years since the discovery of slow earthquakes, new discoveries continue to be made around the world. In recent years, detailed studies of tectonic tremor and SSEs, especially in New Zealand and off the coast of Tohoku, have changed the view that Nankai and Cascades are representative of slow earthquake regions. Slow earthquakes are not uncommon and should be considered as a universal phenomenon that occurs wherever fast earthquakes occur. It is necessary to clarify the boundary between fast and slow earthquakes in the overall seismic phenomenon by using state-of-the-art observations, information science-based analysis methods, and comparative studies of various regions.
Ide et al. (2007) compared seismic moments and durations and identified slow earthquakes as unified ultra-broadband slow earthquakes as opposed to fast earthquakes. There is certainly evidence of broadband slow earthquakes up to about 1000 seconds. However, the occurrence of SSEs without tectonic tremor and the various deformation modes proposed by geology and geophysics suggest that slow earthquakes are not a single physical phenomenon. On the other hand, fast earthquakes always include the interaction between rupture and propagating seismic wave. Since the discovery of slow earthquakes, we may have often regarded earthquakes as normal and slow earthquakes as strange phenomena. However, in fact, among various deformation phenomena, rupture interacting with long-distance propagating waves (fast earthquakes) is the unique process. It is essentially important to find out the material and physical conditions that produce the interaction between rupture and waves.
In addition, forecasting future seismic activity is unavoidable in earthquake research. How does slow earthquakes contribute to the preparation for a huge fast earthquake? A re-examination of seismic activity is underway with the simultaneous occurrence of slow earthquakes in mind. In parallel with the explanation studies using numerical models with differential equations, probabilistic forecast with stochastic processes will also be important. We would like to reach an understanding that will allow us to give more accurate advice on the implications of slow earthquakes in the national earthquake countermeasures.