Coseismic and Postseismic Crustal Deformation Associated With the 2016 Kumamoto Earthquake Sequence Revealed by PALSAR‐2 Pixel Tracking and InSAR

Abstract

Coseismic and postseismic crustal deformations caused by earthquake episodes are important in understanding the mechanisms of these episodes as well as the fault rheology near an epicentral area. Specifically, interferometric synthetic aperture radar (InSAR) and synthetic aperture radar (SAR) pixel tracking can depict high-resolution crustal deformation fields associated with earthquakes and volcanic activities without installing on-site observation instruments. In this study, we investigate the coseismic and postseismic near-fault crustal deformations associated with the 2016 Kumamoto earthquake sequence in southwest Japan using ALOS-2/PALSAR-2 (Phased Array-type L-band SAR-2) data. Coseismic three-dimensional (3-D) displacement fields inferred from PALSAR-2 pixel tracking data showed 1.6 m of horizontal displacements and 2 m of subsidence at maximum, despite the mainshock focal mechanism that was dominated by strike-slip components with N-S extension axes. The locations of large displacement variations along surface ruptures due to the mainshock were almost identical to a region where infrastructure was damaged, thus implying the generation of strong ground seismic waves. By using conventional InSAR stacking, we inferred two independent quasi-east-west and quasi-vertical displacement fields as cumulative postseismic deformations following the mainshock over a period of about 2 years. The near-fault postseismic deformation represented complicated displacement characteristics that could not be explained by a single physical process. Deformation signals around Aso volcano were interpreted by the effects of postseismic physical processes as well as geological heterogeneous structures. Plain Language Summary Coseismic and postseismic crustal deformation fields provide information for inferring slip distributions occurring along a fault, and these data are helpful for understanding the geological characteristics around an epicentral area. By using satellite synthetic aperture radar (SAR) images, we can derive crustal deformation maps with high spatial resolutions and high measurement accuracy without installing on-site observation instruments. In this paper, we offer coseismic and postseismic crustal deformation maps associated with the 2016 Kumamoto earthquake sequence on Kyushu Island, SW Japan, which were derived using the Japanese SAR satellite ALOS-2/PALSAR-2 data. Measurements of displacements along with details on Earth surface ruptures due to earthquakes also allow us to understand the variations in rupture processes along seismogenic faults. Furthermore, comparisons of the spatial and temporal variations of coseismic and postseismic deformations can provide information on the geophysical mechanisms of long-term deformations following a mainshock.

Three-dimensional deformation and its uncertainty derived by integrating multiple SAR data analysis methods

“…However, pre-seismic deformation seems to be sufficiently small given that no significant deformation was observed by the GNSS CORS network and no large seismic event occurred. Although ~ 10 cm post-seismic deformation in Kumamoto has been reported in previous studies (Fujiwara et al 2016;Himematsu and Furuya 2020; Hashimoto 2020; Morishita 2021a), the deformed area was mostly limited where large coseismic deformation occurred and, therefore, the impact of the post-seismic deformation is relatively small. All three methods (i.e., InSAR, SBI, and pixel offset) were applied to each data pair and processed using GSISAR software (Tobita 2003;Morishita et al 2018;Morishita 2019Morishita , 2021b.…”

Ekstraksi Deformasi Koseismik 2.5-D Menggunakan Data Multiple SAR Sentinel-1 (Studi Kasus Gempa Bumi Iran 14 November 2021)

“…Deformasi permukaan dalam tiga dimensi dapat ditentukan dengan beberapa kombinasi beberapa metode berikut (Hu dkk., 2014) : (1) kombinasi teknik SAR interferometri dengan Offset-Tracking (Himematsu & Furuya, 2020), (2) kombinasi teknik SAR interferometri dengan Multiple Aperture Interferometry (MAI) (Baek & Jung, 2020), (3) Multi-pass offset-tracking (De Michele dkk., 2010). Perlu diketahui bahwa metode MAI dan offsettracking memiliki tingkat presisi dan resolusi spasial yang lebih rendah dibandingkan teknik SAR interferometri (Panuntun, 2022).…”

Integrated Investigation on Heterogeneous Lower Crust Rheology in Kyushu and Afterslip Behavior Following the 2016 Mw7.1 Kumamoto Earthquake

“…(2017) proposed that the steady‐state viscosity of the lower crust in Central Kyushu (∼2 × 10 19 Pa s) is lower than the surrounding area (∼2 × 10 20 Pa s), and suggested a weak upper mantle in fore arc that may relates to the shallow fluid release in North Kyushu. Himematsu and Furuya (2020) analyzed 2‐year postseismic deformation with interferometric synthetic aperture radar data, and concluded that the complex near‐field deformation requires consideration of multiple postseismic processes, along with potential influences from geological heterogeneous structure. Moore et al.…”