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

Crustal deformation in central Japan occurs in a highly complex manner characterized by (1) the Itoigawa–Shizuoka Tectonic Line (ISTL), the geologic boundary between the North American and the Eurasian plates, (2) the Niigata–Kobe Tectonic Zone (NKTZ) identified as a strain rate concentration zone by GNSS surveys. The existence of volcanic chain may introduce another complexity through its rheological heterogeneity. In this region, the spatial resolution and accuracy of strain rate mapping by conventional geodetic surveys have been limited by dense vegetation and rugged topography. Here, we integrate L-band InSAR data (2014–2023) with a very dense GNSS network, including private-sector stations, to generate a high-resolution interseismic strain rate map. We identify sharply localized strain rates along the northern ISTL (∼5×10-7 yr-1) and parts of the NKTZ (∼4×10-7 yr-1), which are faster and more spatially confined than GNSS-only estimates. We also find a distinct strain rate concentration (∼3×10-7 yr-1) 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. This is the first InSAR-based strain rate map to resolve fine-scale deformation within a volcanic arc, highlighting the complex deformation style in island arc-trench systems and providing new insights into strain accumulation processes.