[S21] PM-2

[S21-18] Detection of changes in global background and clustering seismicity

*庄 建倉^1,2、熊 子瑶³ (1. 統計数理研究所、2. 総合研究大学院大学先端学術院、3. 中国地震局地質研究所)

The ETAS model is a convenient effective tool to separate background and clustering seismicity from the catalog. While most studies on seismicity modelling focus on a local area, we have developed a spherical version of the ETAS (SETAS, spherical ETAS) model to fit the global seismic events and to detect the global interactive between seismic events from the perspective of the occurrence of earthquake sequences. By fitting the SETAS (spherical ETAS) model to the global seismic events (GMT catalog Mw5.15+), we separate the background seismicity and the earthquake clusters triggered by the major earthquakes in the global scale. The results show that about 1/3 of the global earthquakes with magnitude 5.15 or above are triggered and that the global background seismicity is stationary during the past twenty years. However, locally the background seismicity is tuned by mega earthquakes.

Figure caption: Cumulative frequencies of total seismicity (black), background seismicity (blue) and triggered seismicity (red). Dashed lines represent the occurrence times of Mw8+ earthquakes.