干渉SARで捉えた2014年11月22日長野県北部を震源とする地震に伴う地表変位

抄録

Inland earthquake (Mj 6.7) occurred around Northern Nagano Prefecture in November 22, 2014. Surface ruptures emerged over 9 kilometers or more length intermittently along Kamishiro fault derived from this earthquake. Geospatial Information Authority of Japan (GSI of Japan) implemented the interferometric SAR (InSAR) analysis by using PALSAR-2/ALOS-2 data in the earthquake area after the earthquake. In Addition, GSI of Japan elucidated the crustal deformation induced by the main shock and aftershock activity of the earthquake (GSI of Japan, 2015a). There were some discontinuities of interference phase in the InSAR imageries. We performed a field survey in northern Hakuba Village and Otari Village while referring to the discontinuities of interference phase in the InSAR imageries. At that time, surface displacement wasnʼt reported in Otari Village.

As a result, the appearance position of surface ruptures matched the discontinuities of interference phase on the InSAR imagery in the northern Hakuba Village. Then, we discovered some surface displacements with relative east side uplifting and E-W shortening at the Dorosaki section and west side of JR Chikuni Station in Otari Village. These surface displacements appeared along the discontinuities of interference phase in the InSAR imageries. It is probable that these surface displacements were caused by activity of Himekawa fault. However, it is not clear whether there are surface rupture. These results indicate that InSAR imagery by using PALSAR-2/ALOS-2 data is able to detect surface displacement like surface rupture induced by earthquake. Moreover, InSAR imagery is useful to survey surface displacement widely.