Streak and hierarchical structures of the Tohoku–Hokkaido subduction zone plate boundary

Earth, Planets and Space

Takashi Okuda¹  Satoshi Ide¹ 

[1] Department of Earth and Planetary Science, University of Tokyo;

关键词: Repeating earthquake;    Waveform inversion;    Streak structure;    Hierarchical structure;   

DOI  :  10.1186/s40623-018-0903-8

来源: DOAJ

【 摘 要 】

Abstract Here, we investigated four families of moderate-size (M ~ 4.8) repeating earthquakes and nearby smaller events that occurred in the Naka-Oki, Kushiro-Oki, Urakawa-Oki, and Kamaishi-Oki regions of the Tohoku–Hokkaido subduction zone, Japan, between 2002 and 2017. We employed a hypocenter relocation method based on waveform cross-correlations of the above four families, as well as a waveform inversion method using the empirical Green’s function for the Naka-Oki and Kushiro-Oki earthquakes, where every moderate-size repeating earthquake showed complex and variable rupture processes. However, their rupture areas overlapped significantly and were elongate parallel to the slip direction. Some parts of these areas were also repeatedly ruptured by smaller earthquakes, with these smaller earthquakes and moderate events sometimes following almost identical rupture processes. The results indicate the existence of a characteristic structure that is represented by several elliptical patches that are elongate in the slip direction of the plate interface. It is likely that many streak structures have developed over a 1000 km along-strike section of the plate interface that extends from the Kushiro-Oki region to the Naka-Oki region of the subduction zone. These patches may be distributed hierarchically, with the smaller patches rupturing independently. The rupture of a smaller patch may either stop, producing a small earthquake, or it may grow into a large earthquake, with this rupture process depending on subtle differences in the physical conditions that we are unable to observe in a practical sense. Earthquakes are random processes, but they may not be completely random, as the preexisting characteristic structure of the seismic region may control the rupture process to some degree.

【 授权许可】

Unknown