Interseismic crustal deformation in and around the Atotsugawa fault system, central Japan, detected by InSAR and GNSS

Abstract

The Atotsugawa fault system is one of the best-known active faults in Japan. However, revealing the interseismic velocity field in and around the Atotsugawa fault system with high spatial resolution is challenging because of dense vegetation, steep topography, and heavy snowfall in winter. To overcome these difficulties, we combined ALOS/ PALSAR data and GNSS data from our original stations in addition to the nationwide station network (GEONET). First, we removed the height-dependent phase change in each interferogram using a digital elevation model. Next, we removed the long-wavelength phase trend using the GNSS velocity field. Finally, we applied an InSAR time-series analysis, known as small baseline subset analysis (SBAS), to all the corrected interferograms. The resultant mean velocity field shows a remarkable phase gradient around the Atostugawa fault system. We found a sharp velocity gradient across the Ushikubi fault, a major strand of the Atotsugawa faults system, rather than the main trace of the Atotsugawa fault. Using InSAR, we found that the interseismic deformation inside the strain concentration zone is spatially heterogeneous and different from what we expect from the fault traces.

Surface displacement revealed by L-band InSAR analysis in the Mayya area, Central Yakutia, underlain by continuous permafrost

“…Major InSAR time-series analysis methods, such as the small baseline subset (SBAS) approach (Berardino et al 2002), persistent scatterer InSAR (PS-InSAR) technique (Ferretti et al 2001), and a combination of the two (Hooper 2008), were originally applied to derive small displacements such as inter-seismic deformation (e.g., Takada et al 2018) and land subsidence (e.g., Ishitsuka et al 2014). These methods are useful for identifying not only linear trends of surface displacement but also cyclic trends (seasonal changes) using fitting trigonometric functions and inversion algorithms.…”

Surface creep rate distribution along the Philippine fault, Leyte Island, and possible repeating of Mw ~ 6.5 earthquakes on an isolated locked patch

“…This step is an alternative to the method described above, and is not conducted in the present study. This method has been proposed by Fukushima and Hooper (2011) and used by Takada et al (2018). The method is explained here for clarifying the relation with the alternative method.…”

Crustal dynamics: unified understanding of geodynamic processes at different time and length scales

“…Major recent earthquake ruptures appear to follow anticipated trajectories of conjugate Riedel shears within the shear zone. Takada et al (2018) employed Satellite Geodesy (InSAR and GNSS) to define a sharp velocity gradient across the Ushikubi fault within the dextral Atotsugawa fault system in central Japan. Analysis of InSAR data shows interseismic deformation to be spatially heterogeneous within the strain concentration zone.…”