Calculation of coseismic displacement from lidar data in the 2016 Kumamoto, Japan, earthquake

Abstract

Abstract. The spatial distribution of the coseismic displacements that occurred along the Futagawa fault during the 2016 Kumamoto earthquake of M w 7.0 was estimated using airborne light detection and ranging (lidar) data. In this study, a pair of digital surface models (DSMs) obtained from the high-density lidar data before and after the mainshock on 16 April 2016 were used. A window matching search approach based on the correlation coefficient between the two DSMs was used to estimate the geodetic displacement in the near-field region. The results showed good agreements with the geodetic displacements calculated from strong-motion acceleration records and coincided with the fault line surveyed by the Geological Survey of Japan. IntroductionOn 14 April 2016, an M w 6.2 earthquake struck Kumamoto Prefecture, Japan, at 21:26 JST. The epicenter was located at the end of the Hinagu fault at a shallow depth. After approximately 28 h (at 01:25 on 16 April 2016), another earthquake of M w 7.0 struck the Futagawa fault, which is near the Hinagu fault. The first event was designated as the foreshock and the second one as the mainshock. Both the events occurred in the town of Mashiki (with a population of approximately 33 000), which is located to the east of Kumamoto City (with a population of approximately 735 000). Many aftershocks followed these events, and as of 6 September, 4 months after the foreshock, the total number of aftershocks (larger than M w 3.5) is 272. This number is the largest among the recent inland (crustal) earthquakes in Japan (Japan Meteorological Agency, 2016). This Kumamoto earthquake sequence triggered secondary effects such as landslides and liquefaction and caused extensive damage to lifeline systems, buildings, bridges, and transportation structures. A total of 8550 buildings, mostly in Kumamoto Prefecture, were seriously damaged or collapsed, and 50 human lives were lost, mostly because of landslides or the collapse of buildings (Cabinet Office of Japan, 2016).Soon after the occurrence of the foreshock, various satellites and airborne remote sensing technologies were employed to monitor crustal movements and various damages . The Japan Aerospace Exploration Agency (JAXA) carried out extensive monitoring of the source area using the PALSAR-2 sensor on board ALOS-2 satellite. Interferometric synthetic aperture radar (InSAR) analysis using a pair of imagery data obtained from PALSAR-2 before (pre-event data) and after (postevent data) the mainshock showed the line-of-sight (LOS) displacements to the satellite direction (Geospatial Information Authority of Japan, 2016). Using the pre-event data (30 November 2015, 7 March 2016 and the co-event data (7 March, 18 April 2016) from PALSAR-2, the authors of this paper calculated the spatial coherence values (International Charter, 2016), which could highlight the extensive landslides and severe damages to buildings along the Futagawa fault line.After the Kumamoto earthquake, government agencies and aerial survey companies in Japan conducted several ...

The M7 2016 Kumamoto, Japan, Earthquake: 3‐D Deformation Along the Fault and Within the Damage Zone Constrained From Differential Lidar Topography

“…The 3‐D ICP displacement field shows that the Kumamoto earthquake accommodated right‐lateral and northwest side down motion (Figure ), in agreement with earlier results (Moya et al, ; Shirahama et al, ; Toda et al, ). The ICP analysis also reveals sections of off‐fault deformation that were not mapped in the field.…”

The 2016 M7 Kumamoto, Japan, Earthquake Slip Field Derived From a Joint Inversion of Differential Lidar Topography, Optical Correlation, and InSAR Surface Displacements

“…The right-lateral M ja 6.5 (M w 6.2) and M ja 6.4 (M w 6.0) foreshocks of 14 and 15 April, respectively, ruptured the northern part of the Hinagu Fault (T. Kobayashi, 2017). The 16 April M ja 7.3 (M w 7.0) mainshock propagated ENE for~40 km along the Hinagu and the adjacent NNW dipping Futagawa Fault, with right-lateral and normal (uplift to the southeast) motion (Kubo et al, 2016;Moya et al, 2017;Shirahama et al, 2016). The earthquake ruptured the left-lateral conjugate shear zone and bifurcated into northern and southern ruptures that accommodate dominantly right-lateral and vertical motion ( Figure 1b: Bi), respectively (Shirahama et al, 2016).…”

Detection of collapsed buildings from lidar data due to the 2016 Kumamoto earthquake in Japan

“…A direct comparison of the BDSM and ADSM shows that the building coordinates do not match because the ADSM contains coseismic displacements. Therefore, the ADSM was shifted before detecting the damaged buildings based on the permanent crustal movement calculated by Moya et al (2017). To do this, an automated procedure for calculating the permanent three-dimensional (3-D) displacement was implemented.…”

“…Only buildings with footprint areas greater than 20 m 2 were evaluated. Because the point densities of the BDSM and ADSM are different and the footprint Comparison between the coseismic displacements estimated from the lidar data (Moya et al, 2017) and from field measurements (Geospatial Information Authority of Japan, 2016). data include some errors, perfect matching of the DSMs with the building footprints could not be achieved.…”

“…Among the several remote-sensing technologies used to monitor the area affected by the Kumamoto earthquake , a pair of lidar data sets taken before and after the mainshock were available (Moya et al, 2017). As mentioned before, this kind of data set is not often available.…”