Stress transferred by the 1995 Mw = 6.9 Kobe, Japan, shock: Effect on aftershocks and future earthquake probabilities
Stress transferred by the 1995 Mw = 6.9 Kobe, Japan, shock: Effect on aftershocks and future earthquake probabilities
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DOI：
10.1029/98jb00765
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发表时间：
1998-10
影响因子：
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通讯作者：
S. Toda;R. Stein;P. Reasenberg;J. Dieterich;A. Yoshida
中科院分区：
文献类型：
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作者：
S. Toda;R. Stein;P. Reasenberg;J. Dieterich;A. Yoshida
神户地震发生在日本西南部人口稠密的大阪-京都走廊边缘。我们研究地震如何将应力转移到附近的断层，改变它们的破坏程度，从而改变地震概率。我们发现，相对于神户地震前的地震活动，神户余震集中在计算出的库仑应力增加的区域，而在应力减少的区域则不太常见。我们通过形成地震活动率变化和库仑应力变化之间的空间相关性来量化这种关系。对于大于 0.2-1.0 巴 (0.02-0.1 MPa) 的应力变化，这种相关性非常显着，并且地震活动率变化对应力变化的非线性依赖性与地震发生的状态和速率相关公式相一致。我们通过求解神户 100 公里范围内主要断层上的应力变化并计算这些应力变化引起的概率变化，将这种分析扩展到未来的主震。应力变化的瞬态效应被状态相关的本构关系纳入，放大了余震期间的永久应力变化。以这种方式构建的地震概率高度依赖于时间，比当前实践中假设的要严重得多。由于概率取决于主要断层的几个鲜为人知的参数，因此我们通过蒙特卡罗模拟来估计概率的不确定性。这使我们能够包含自上次地震以来经过的时间、重复时间及其变异性以及余震衰减周期的不确定性。我们估计，经计算，京都附近有马-高槻构造线 (ATTL) 东段的应力增加了 3 巴 (0.3-MPa)，导致京都附近随后发生大地震的 30 年概率增加了五倍； ATTL 西段应力降低 2 巴（0.2 兆帕），导致概率降低 140 至 2000 倍。1997 年至 2007 年期间，大阪周边 50 公里范围内发生 Mw = 6.9 级地震的概率估计从神户地震前的 5-6% 上升至神户地震后的 7-11%； 1997-2027年间，这一比例预计从科比之前的14-16%上升至16-22%。
The Kobe earthquake struck at the edge of the densely populated Osaka-Kyoto corridor in southwest Japan. We investigate how the earthquake transferred stress to nearby faults, altering their proximity to failure and thus changing earthquake probabilities. We find that relative to the pre-Kobe seismicity, Kobe aftershocks were concentrated in regions of calculated Coulomb stress increase and less common in regions of stress decrease. We quantify this relationship by forming the spatial correlation between the seismicity rate change and the Coulomb stress change. The correlation is significant for stress changes greater than 0.2–1.0 bars (0.02–0.1 MPa), and the nonlinear dependence of seismicity rate change on stress change is compatible with a state- and rate-dependent formulation for earthquake occurrence. We extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of Kobe and calculating the change in probability caused by these stress changes. Transient effects of the stress changes are incorporated by the state-dependent constitutive relation, which amplifies the permanent stress changes during the aftershock period. Earthquake probability framed in this manner is highly time-dependent, much more so than is assumed in current practice. Because the probabilities depend on several poorly known parameters of the major faults, we estimate uncertainties of the probabilities by Monte Carlo simulation. This enables us to include uncertainties on the elapsed time since the last earthquake, the repeat time and its variability, and the period of aftershock decay. We estimate that a calculated 3-bar (0.3-MPa) stress increase on the eastern section of the Arima-Takatsuki Tectonic Line (ATTL) near Kyoto causes fivefold increase in the 30-year probability of a subsequent large earthquake near Kyoto; a 2-bar (0.2-MPa) stress decrease on the western section of the ATTL results in a reduction in probability by a factor of 140 to 2000. The probability of a Mw = 6.9 earthquake within 50 km of Osaka during 1997–2007 is estimated to have risen from 5–6% before the Kobe earthquake to 7–11% afterward; during 1997–2027, it is estimated to have risen from 14–16% before Kobe to 16–22%.