Source rupture process of the 2018 Hokkaido Eastern Iburi earthquake deduced from strong-motion data considering seismic wave propagation in three-dimensional velocity structure

The source rupture process of the 2018 Hokkaido Eastern Iburi earthquake (MJMA 6.7) was analyzed by a kinematic waveform inversion method using strong-motion data in 0.04–0.5 Hz. This earthquake occurred close to the Hidaka Collision Zone and the Ishikari depression, where the crustal structure is rather complex. Thus, we used a three-dimensional velocity structure model to compute the theoretical Green’s functions by the finite difference method. A source fault model with strike-angle variation was set based on the spatial distribution of the early aftershocks. The strong-motion stations used for the source inversion were selected based on the result of forward ground motion simulation of a moderate aftershock. The slip in the first 5 s was relatively small, but an area of significant slip with peak slip of 1.7 m was found in the depth range from 22 to 32 km. The rupture propagated upward mainly in the southwest direction. Based on the regional crustal structure and the configuration of the Moho discontinuity, the large-slip area was thought to be located in the lower crust, and its rupture did not reach the upper part of the continental crust. Most of the early aftershocks occurred around the large-slip area. The later aftershocks at the depth shallower than 20 km occurred outside the causative source fault of the mainshock. Three-dimensional ground motion simulation demonstrated that the heterogeneous source process and the three-dimensional basin and crustal velocity structure brought a large velocity pulse to an area to the southwest of the source fault, where the largest PGV was observed during the mainshock. The spatial distribution of the simulated PGV resembled the observed PGV distribution except some sites located inside the Ishikari depression where thick Quaternary soft low-velocity sediments exist at the top of the basin.

[1]  K. Hatayama,et al.  Control Factors of Spatial Variation of Long-Period Strong Ground Motions in the Yufutsu Sedimentary Basin, Hokkaido, during the Mw 8.0 2003 Tokachi-oki, Japan, Earthquake , 2007 .

[2]  Robert W. Graves,et al.  Resolution analysis of finite fault source inversion using one- and three-dimensional Green's functions. 1. Strong motions , 2001 .

[3]  R. Archuleta,et al.  A new nonlinear finite fault inversion with three-dimensional Green's functions: Application to the 1989 Loma Prieta, California, earthquake , 2004 .

[4]  Hiromitsu Yamagishi,et al.  Landslides by the 2018 Hokkaido Iburi-Tobu Earthquake on September 6 , 2018, Landslides.

[5]  D. Wald,et al.  Spatial and temporal distribution of slip for the 1992 Landers, California, earthquake , 1994, Bulletin of the Seismological Society of America.

[6]  Hiromitsu Nakamura,et al.  Deployment of New Strong Motion Seismographs of K-NET and KiK-net , 2011 .

[7]  Jianghai Xia,et al.  Application of the multiaxial perfectly matched layer (M-PML) to near-surface seismic modeling with Rayleigh waves , 2011 .

[8]  Hiroyuki Fujiwara,et al.  Recent Progress of Seismic Observation Networks in Japan , 2004 .

[9]  Jean-Paul Ampuero,et al.  A New Strategy to Compare Inverted Rupture Models Exploiting the Eigenstructure of the Inverse Problem , 2015 .

[10]  Junichi Nakajima,et al.  High‐resolution seismic velocity structure beneath the Hokkaido corner, northern Japan: Arc‐arc collision and origins of the 1970 M 6.7 Hidaka and 1982 M 7.1 Urakawa‐oki earthquakes , 2012 .

[11]  T. Iwata,et al.  Source rupture processes of the foreshock and mainshock in the 2016 Kumamoto earthquake sequence estimated from the kinematic waveform inversion of strong motion data , 2016, Earth, Planets and Space.

[12]  K. Koketsu,et al.  Source Process of the 1923 Kanto Earthquake Considering Subduction Interface Geometry and Amplification Effects Caused by the Large‐Scale and 3D Complex Sedimentary Basin , 2016 .

[13]  Takeo Moriya,et al.  Upper and middle crustal deformation of an arc - Arc collision across Hokkaido, Japan, inferred from seismic refraction/wide-angle reflection experiments , 2004 .

[14]  Andrew Jarvis,et al.  Hole-filled SRTM for the globe Version 4 , 2008 .

[15]  N. Takai,et al.  Cause of destructive strong ground motion within 1–2 s in Mukawa town during the 2018 Mw 6.6 Hokkaido eastern Iburi earthquake , 2019, Earth, Planets and Space.

[16]  Fourth-order finite-difference PW seismograms , 2001 .

[17]  G. Kimura.  Oblique subduction and collision: Forearc tectonics of the Kuril arc , 1986 .

[18]  Gaku Kimura,et al.  Collision orogeny at arc‐arc junctions in the Japanese Islands , 1996 .

[19]  Kojiro Irikura,et al.  Fault Geometry at the Rupture Termination of the 1995 Hyogo-ken Nanbu Earthquake , 2000 .

[20]  Kimiyuki Asano,et al.  Development of fully Bayesian multiple-time-window source inversion , 2016 .

[21]  Charles L. Lawson,et al.  Solving least squares problems , 1976, Classics in applied mathematics.

[22]  Masashi Matsuoka,et al.  A Weighted Overlay Method for Liquefaction-Related Urban Damage Detection: A Case Study of the 6 September 2018 Hokkaido Eastern Iburi Earthquake, Japan , 2018, Geosciences.

[23]  K. Koketsu,et al.  Analysis of the rupture process of the 1995 Kobe earthquake using a 3D velocity structure , 2013, Earth, Planets and Space.

[24]  Göran Ekström,et al.  The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes , 2012 .

[25]  B. Kennett,et al.  Seismic waves in a stratified half space. , 1979 .

[26]  Shui-Beih Yu,et al.  Spatial and Temporal Distribution of Slip for the 1999 Chi-Chi, Taiwan, Earthquake , 2004 .

[27]  Takuo Maruyama,et al.  On the force equivalences of dynamic elastic dislocations with reference to the earthquake mechanisms , 1963 .

[28]  Y. Nishida,et al.  Crustal structure and tectonics of the Hidaka Collision Zone, Hokkaido (Japan), revealed by vibroseis seismic reflection and gravity surveys , 1998 .

[29]  Shingo Yoshida,et al.  Joint Inversion of Near- and Far-field Waveforms and Geodetic Data for the Rupture Process of the 1995 Kobe Earthquake , 1996 .

[30]  Shiann-Jong Lee,et al.  Anomalously Large Ground Motion in the 2016 ML 6.6 Meinong, Taiwan, Earthquake: A Synergy Effect of Source Rupture and Site Amplification , 2016 .

[31]  Hirotugu Akaike,et al.  Likelihood and the Bayes procedure , 1980 .

[32]  Takeshi Kimura,et al.  Peak ground motions and characteristics of nonlinear site response during the 2018 Mw 6.6 Hokkaido eastern Iburi earthquake , 2019, Earth, Planets and Space.

[33]  Thomas H. Heaton,et al.  Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake , 1983 .

[34]  H. Saomoto,et al.  Modelling of wave propagation and attenuation in the Osaka sedimentary basin, western Japan, during the 2013 Awaji Island earthquake , 2016 .

[35]  S. Somala,et al.  Finite-fault source inversion using adjoint methods in 3D heterogeneous media , 2018 .

[36]  A. Levander.  Fourth-order finite-difference P-SV seismograms , 1988 .

[37]  Robert W. Graves,et al.  Simulating seismic wave propagation in 3D elastic media using staggered-grid finite differences , 1996, Bulletin of the Seismological Society of America.

[38]  D. Suetsugu,et al.  Re-examination of fault model for the 1982 Urakawa-Oki earthquake by analyses of seismic, geodetic, and tsunami data , 1988 .

[39]  T. Iwata,et al.  Source-Rupture Process of the 2007 Noto Hanto, Japan, Earthquake Estimated by the Joint Inversion of Strong Motion and GPS Data , 2011 .

[40]  Haruko Sekiguchi,et al.  Rupture process of the 2011 Tohoku‐Oki mega‐thrust earthquake (M9.0) inverted from strong‐motion data , 2011 .

[41]  Allen H. Olson,et al.  Finite faults and inverse theory with applications to the 1979 Imperial Valley earthquake , 1982 .

[42]  S. Aoi,et al.  Three‐dimensional finite difference simulation of long‐period ground motions for the 2003 Tokachi‐oki, Japan, earthquake , 2008 .

[43]  Hiroshi P. Sato,et al.  Configuration of the Moho discontinuity beneath the Japanese Islands derived from three-dimensional seismic tomography , 2017 .

[44]  Reo Kimura,et al.  The 2018 Hokkaido Eastern Iburi Earthquake and its Aftermath , 2019, Journal of Disaster Research.

[45]  T. Moriya,et al.  Collision structure in the upper crust beneath the southwestern foot of the Hidaka Mountains, Hokkaido, Japan as derived from explosion seismic observations , 1998 .

[46]  Remko Scharroo,et al.  Generic Mapping Tools: Improved Version Released , 2013 .

[47]  Estimation of sales decrease caused by a disaster: Hokkaido blackout after earthquake in 2018 , 2019, Journal of Computational Social Science.

[49]  Leon Knopoff,et al.  Body Force Equivalents for Seismic Dislocations , 1964 .

[50]  M. Bouchon.  A simple method to calculate Green's functions for elastic layered media , 1981 .

[51]  Kristel C. Meza-Fajardo,et al.  A Nonconvolutional, Split-Field, Perfectly Matched Layer for Wave Propagation in Isotropic and Anisotropic Elastic Media: Stability Analysis , 2008 .

[52]  Chen Ji,et al.  Efficient Inversions for Earthquake Slip Distributions in 3D Structures , 2016 .

[53]  Danijel Schorlemmer,et al.  The Earthquake‐Source Inversion Validation (SIV) Project , 2016 .

[54]  T. Furumura,et al.  Damaging Long-period Ground Motions from the 2003 Mw 8.3 Tokachi-oki, Japan Earthquake , 2005 .

[55]  C. Lawson,et al.  Solving least squares problems , 1976, Classics in applied mathematics.

[56]  R. Takagi,et al.  Coseismic changes in subsurface structure associated with the 2018 Hokkaido Eastern Iburi Earthquake detected using autocorrelation analysis of ambient seismic noise , 2019, Earth, Planets and Space.

[57]  J. Kristek,et al.  3D Heterogeneous Staggered-grid Finite-difference Modeling of Seismic Motion with Volume Harmonic and Arithmetic Averaging of Elastic Moduli and Densities , 2002 .

[58]  P. Martin Mai,et al.  SRCMOD: An Online Database of Finite‐Fault Rupture Models , 2014 .