发表机构
Farhangian University; Ankara University; University of Beira Interior; Atmosphere and Ocean Research Institute (AORI), the University of Tokyo（法尔干大学; 安卡拉大学; 贝拉内陆大学; 东京大学大气海洋研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过分析2016年熊本Mw 7.0地震序列的b值、分形维数和Z值，揭示了断层锁定、破裂释放及愈合过程，为地震危险性评估提供了新框架。
AI 中文摘要
理解地壳断层如何积累应变、成核破裂并重新分配震后应力，对于地震危险性评估至关重要。2016年4月16日发生的Mw 7.0熊本地震，破裂了日本九州中部别府-岛原地堑中的布田川-日奈久断裂带，为追踪整个地震周期的这些过程提供了极佳的数据集。我们使用日本气象厅目录（2014-2018年）并采用动态完整性估计（Mc≈2.15-2.25），研究了Gutenberg-Richter b值、三维震源分形维数（Dc）和地震活动率异常（Z值）。在震前一至两年的准备阶段，b值从基线1.35±0.10下降至前兆最小值0.59，而Dc从0.85±0.15收缩至0.70-0.80，记录了应力集中和微破裂合并到狭窄的成核区。沿地堑形成了连贯的负Z值异常（-1.6至-2.0），并随积分时间增强——这与渐进式断层锁定一致，尽管并非其证据。深度切片显示低b值锁定核（b≤0.65）分层于10-12.5公里深度，并在破裂前最后四个月内变得更加尖锐。破裂在数周内逆转了这一趋势：b值激增至1.25-1.35，Dc扩展至2.04-2.11，与同震应力降和余震激活一致，随后在2.5年内恢复。横截面显示余震急剧定位，同时在日奈久终止端和阿苏山附近存在两个未松弛的凹凸体（b≈0.80-0.95），与正库仑应力加载一致。该框架比任何单一指标都能更好地解析凹凸体的锁定、释放和愈合；然而，由于异常是回顾性识别的，它们应被视为连贯行为的证据，而非单独作为经过验证的预测工具。
英文摘要
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 ($M_c \approx 2.15$--$2.25$), 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 $1.35 \pm 0.10$ to a precursory minimum of $0.59$, while $D_c$ contracted from $0.85 \pm 0.15$ 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 ($b \le 0.65$) 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 ($b \approx 0.80$--$0.95$) 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.
