The 2016 Mw 7.0 Kumamoto Earthquake Sequence, Japan revisited: Insights from Spatio-Temporal Analysis of Seismicity Parameters
Abstract
Understanding how crustal faults accumulate strain, nucleate ruptures, and redistribute post-seismic stress is fundamental to seismic hazard assessment. The 16 April 2016 Mw 7.0 Kumamoto earthquake, rupturing the Futagawa--Hinagu fault zone in the Beppu--Shimabara graben, central Kyushu, Japan, offers a premier dataset for tracking these processes across a full earthquake cycle. Using the JMA catalog (2014--2018) with dynamic completeness estimation (Mc ≈ 2.15--$2.25$), we examine the Gutenberg--Richter b-value, the 3-D hypocentral fractal dimension (Dc), and the seismicity-rate anomaly (Z-value). During the one- to two-year preparatory phase, b declined from a baseline of 1.35 ± 0.10 to a precursory minimum of $0.59$, while Dc contracted from 0.85 ± 0.15 to $0.70−−0.80$, recording stress concentration and microfracture coalescence onto a narrow nucleation zone. A coherent negative Z-value anomaly (-1.6 to -2.0) developed along the graben, strengthening with integration time---consistent with, though not proof of, progressive fault locking. Depth-sliced volumes show the low-b locked core (b ≤ 0.65) was stratified at $10−−12.5$~km depth and sharpened within the final four months before failure. Rupture reversed this within weeks: b surged to $1.25−−1.35$ and Dc expanded to $2.04−−2.11$, consistent with coseismic stress drop and aftershock activation, followed by recovery over 2.5 years. Cross-sections reveal sharp aftershock localization alongside two unrelaxed asperities (b ≈ 0.80--$0.95$) near the Hinagu termination and Mount Aso, consistent with positive Coulomb stress loading. This framework resolves asperity locking, release, and healing better than any single metric; however, since anomalies were identified retrospectively, they should be read as evidence of coherent behavior rather than a validated forecast tool alone.
Related
- Advance identification of where the 2026 Kumamoto earthquake would begin
- Time-Resolved Surface-Fault Displacement During the 2026 Kumamoto Earthquake From Near-Fault Video
- On-Fault Parameters and Fault Connectivity Control Synthetic Earthquake Catalogs and 30-Year Rupture Probabilities in RSQSim Simulations of the Eastern San Francisco Bay Area
- Extracting and Characterizing Near-Fault Effects from Strong Motion Observations of the 2022 Chishang Earthquake Sequence
- Development of a Combined Detection and Relocation Workflow (TM2DD) to Characterize Escalating Hydraulic Fracturing Induced Seismicity in the Karnes Trough Fault Zone of the Eagle Ford Shale Play, Texas
BibTeX
@misc{mohammadigheymasi20262016,
title = {{The 2016 Mw 7.0 Kumamoto Earthquake Sequence, Japan revisited: Insights from Spatio-Temporal Analysis of Seismicity Parameters}},
author = {Hamzeh Mohammadigheymasi and Muhammed Hossein Mousavi and Marjan Tourani and Nasrin Tavakolizadeh},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.06911},
eprint = {2609.06911},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.06911},
}
RIS
TY - UNPB
TI - The 2016 Mw 7.0 Kumamoto Earthquake Sequence, Japan revisited: Insights from Spatio-Temporal Analysis of Seismicity Parameters
AU - Hamzeh Mohammadigheymasi
AU - Muhammed Hossein Mousavi
AU - Marjan Tourani
AU - Nasrin Tavakolizadeh
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.06911
UR - https://arxiv.org/abs/2609.06911
AB - Understanding how crustal faults accumulate strain, nucleate ruptures, and redistribute post-seismic stress is fundamental to seismic hazard assessment. The 16 April 2016 M_w 7.0 Kumamoto earthquake, rupturing the Futagawa--Hinagu fault zone in the Beppu--Shimabara graben, central Kyushu, Japan, offers a premier dataset for tracking these processes across a full earthquake cycle. Using the JMA catalog (2014--2018) with dynamic completeness estimation (M_c ≈ 2.15--$2.25$), we examine the Gutenberg--Richter b-value, the 3-D hypocentral fractal dimension (D_c), and the seismicity-rate anomaly (Z-value). During the one- to two-year preparatory phase, b declined from a baseline of 1.35 ± 0.10 to a precursory minimum of $0.59$, while D_c contracted from 0.85 ± 0.15 to $0.70−−0.80$, recording stress concentration and microfracture coalescence onto a narrow nucleation zone. A coherent negative Z-value anomaly (-1.6 to -2.0) developed along the graben, strengthening with integration time---consistent with, though not proof of, progressive fault locking. Depth-sliced volumes show the low-b locked core (b ≤ 0.65) was stratified at $10−−12.5$~km depth and sharpened within the final four months before failure. Rupture reversed this within weeks: b surged to $1.25−−1.35$ and D_c expanded to $2.04−−2.11$, consistent with coseismic stress drop and aftershock activation, followed by recovery over 2.5 years. Cross-sections reveal sharp aftershock localization alongside two unrelaxed asperities (b ≈ 0.80--$0.95$) near the Hinagu termination and Mount Aso, consistent with positive Coulomb stress loading. This framework resolves asperity locking, release, and healing better than any single metric; however, since anomalies were identified retrospectively, they should be read as evidence of coherent behavior rather than a validated forecast tool alone.
ER -