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

Abstract

Three‐dimensional near‐fault coseismic deformation fields from high‐resolution differential topography provide new information on the behavior of the shallow fault zone in large surface‐rupturing earthquakes. Our work focuses on the 16 April 2016 Mw 7.0 Kumamoto, Japan, earthquake, which ruptured ~40 km of the Futagawa‐Hinagu Fault Zone on Kyushu Island with an oblique strike‐slip mechanism and surface offset exceeding 2 m. Our differential lidar analysis constrains the structural style of strain accommodation along the primary fault trace and the surrounding damage zone. We show that 36 ± 29% and 62 ± 32% of the horizontal and vertical deformation, respectively, was accommodated off the principal fault trace. The horizontal strains of up to 0.03 suggest that the approximate elastic strain limit was exceeded over a ~250 m width in many locations along the rupture. The inelastic deformation of the fault volume produced the observed distributed deformation at the Earth's surface. We demonstrate a novel approach for calculating 3‐D displacement uncertainties, indicating errors of centimeters to a few decimeters for displacements computed over 50 m horizontal windows. Errors correlate with land cover and relief, with flatter agricultural land associated with the highest displacement uncertainty. These advances provide a framework for future analyses of shallow earthquake behavior using differential topography.

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

“…We interpret this observation to reflect a slip deficit along the primary fault trace yet not a shallow strain deficit in the 3-D fault volume. was accommodated off the principal fault, and the region of inelastic deformation straddled the fault by 250 m (Scott et al, 2018). Map view images of the slip distribution from (g) the lidar-optical-InSAR and (h) the optical-InSAR source inversion in this study as well as from (i) Asano and Iwata (2016) and (j) H. Kobayashi et al (2017).…”

“…Map view images of the slip distribution from (g) the lidar-optical-InSAR and (h) the optical-InSAR source inversion in this study as well as from (i) Asano and Iwata (2016) and (j) H. Kobayashi et al (2017). Likely, the off-fault deformation was accommodated as volume change (Scott et al, 2018) and as slip along secondary faults in a flower-like structure that was not explicitly included in the fault geometry. The black circle in Figure 4g is the 14 April M JMA 6.5 foreshock epicenter location.…”

“…Recent advances in geodetic imaging have filled a previous near-fault data gap to reveal coseismic and postseismic surface deformation along faults and in the surrounding fault volume (Brooks et al, 2017;DeLong et al, 2016;Milliner et al, 2015;Nissen et al, 2012Nissen et al, , 2014Oskin et al, 2012;Scott et al, 2018;Vallage et al, 2015). Inferences of both depleted and elevated shallow slip and off-fault deformation along strike and at depth in different earthquakes have raised questions about the strain budget throughout the seismic cycle.…”

Characterizing Complex Surface Ruptures in the 2013 Mw 7.7 Balochistan Earthquake Using Three‐Dimensional Displacements

“…This method is designed to process dense and accurate LiDAR point clouds. Nissen et al (2012Nissen et al ( , 2014, Glennie et al (2014), and Scott et al (2018) obtained good 3-D deformation fields based on ICP. In this study, the ALOS DEM that we purchased is in raster format and has a much lower resolution and vertical accuracy than LiDAR data (5 m versus tens of centimeters).…”

Three‐Dimensional Surface Displacements During the 2016 MW 7.8 Kaikōura Earthquake (New Zealand) From Photogrammetry‐Derived Point Clouds

“…We use an adaptation of the ICP algorithm (Besl & McKay, 1992;Chen & Medioni, 1992) to retrieve the 3-D deformation field that matches our 2014-2015 point cloud to our 2016-2017 point cloud. The use of this algorithm to extract coseismic displacements from preearthquake and postearthquake lidar point clouds is now fairly routine and described in detail elsewhere (e.g., Ekhtari & Glennie, 2018;Nissen et al, 2012Nissen et al, , 2014Scott et al, 2018). Our purpose is not to test the ICP algorithm.…”