Temporal stability of coda Q in the northeastern part of an inland high strain rate zone, central Japan: implication of a persistent ductile deformation in the crust

• Main Authors: Masanobu Dojo, Yoshihiro Hiramatsu
• Format: Article
• Language: English
• Published: SpringerOpen 2019-03-01
• Series: Earth, Planets and Space
• Subjects: Niigata–Kobe Tectonic Zone; Heterogeneity; Aseismic deformation; The 2011 Tohoku earthquake
• Online Access: http://link.springer.com/article/10.1186/s40623-019-1013-y

Abstract We have analyzed the temporal variation in coda Q in the northeastern part of an inland high strain rate zone, the Niigata–Kobe Tectonic Zone (NKTZ), in central Japan, to investigate the response of coda Q to the modification of the strain field induced by the 2011 Tohoku earthquake (Mw 9.0). We observe no statistically significant temporal variations in the spatial distribution of coda Q as the whole analyzed area, implying that the crustal deformation induced by the 2011 Tohoku earthquake has provided no significant temporal variation in crustal heterogeneity as the whole analyzed area. For the middle frequency bands, before and after the 2011 Tohoku earthquake, we have commonly found a negative correlation between the spatial distributions of coda Q and the differential strain rate and a positive correlation between the spatial distributions of coda Q and the perturbation of S-wave velocity in the upper crust. These features, together with previous works, suggest that the ductile deformation with a high rate in the upper crust plays an important role in generating the high strain rate in the analyzed area not only before but also after the 2011 Tohoku earthquake. In other words, the existence of a persistent ductile deformation in the upper crust contributes essentially to the generation process of the high strain rate in the northeastern part of the NKTZ. It is important to note that the location of the persistent ductile deformation in the northeastern part of the NKTZ, mainly in the upper crust, differs from that in the central part of the NKTZ, mainly in the lower crust.