Detection of Surface Rupture and Deformation Associated with the 2014 Kamishiro Fault Earthquake in Central Japan by Differential LiDAR and Tectonic Geomorphological Survey

Abstract:

LiDAR can be used to obtain elevation data for areas spread over several kilometers, and it has a spatial resolution of a few tens of centimeters. Therefore, it is suitable for detecting the surface deformation associated with inland earthquakes. We applied this technique to assess surface deformation associated with the 2014 Kamishiro fault earthquake (Mw6.3) in central Japan. High-resolution LiDAR data was obtained before and after the earthquake, and therefore we can analyze the difference. Our results revealed the crustal movement distribution over a wide area and surface ruptures associated with the earthquake.

As a result, surface deformation that has been detected by LiDAR is consistent with what has been confirmed as surface ruptures by our field survey. Since the ruptures were often accompanied by broader deformation with wavelength on the order of tens of meters, a sufficiently wide range of surveying tools, including a total station or UAVs, was required to evaluate the entire deformation in the field survey. The observed amount of relative east-side-up displacement can be up to 1 m in the field, and that of the left-lateral offset was less than 1 m. Differential LiDAR is advantageous in that we can evaluate not only relative but absolute desplacement along the fault line.

The Kamishiro fault forms the northernmost part of the Itoigawa-Shizuoka Tectonic Line, one of the most dominant active faults in Japan. Here, a displacement of more than 3 m has been estimated to occur once in a thousand years by previous studies. However, the displacement observed after the 2014 earthquake was less than one-third of the estimated value. Therefore, it is necessary to reconsider the characteristic earthquake associated with the Kamishiro fault. In addition, strong ground motion of seismic intensity 7 occurred locally in the Kamishiro basin. It should be noted that similar damage is recorded to have occurred in this region following the 1714 earthquake.