High-resolution strain rate mapping around inland plate boundary within a volcanic arc using L-band InSAR and dense GNSS networks

Crustal deformation in central Japan occurs in a highly complex manner characterized by the Itoigawa-Shizuoka Tectonic Line (ISTL), the geologic boundary between the North American and the Eurasian plates. In addition, a prominent strain concentration zone, known as the Niigata-Kobe tectonic zone (NKTZ), has been identified by GNSS surveys. The existence of a volcanic chain introduces another complexity through its rheological heterogeneity. In this region, the spatial resolution and accuracy of strain rate mapping by conventional ground-based geodetic surveys have been limited by dense vegetation and rugged topography. Here, we integrate L-band InSAR data (2014-2023), which can resolve deformation in densely vegetated mountainous areas where ground-based measurements alone are spatially sparse, with GNSS data from a dense network (average spacing of [Formula: see text]) including private-sector stations, to generate a high-resolution interseismic strain rate map. We identify sharply localized strain rates along the northern ISTL ([Formula: see text]) and parts of the NKTZ ([Formula: see text]), which are of larger magnitude and more spatially confined than GNSS-only estimates. We also find a distinct strain rate concentration ([Formula: see text]) along the southern extension of the Hida Mountains volcanic zone. Some of these concentrated strain rate zones align with known active faults, while others do not (e.g., the southern extension of the Hida range). This study presents the first L-band InSAR-based strain rate map in a densely vegetated mountainous region, revealing the complex deformation style in volcanic arcs and providing new insights into strain accumulation processes.