Space‐time model for regional seismicity and detection of crustal stress changes
Space‐time model for regional seismicity and detection of crustal stress changes
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DOI：
10.1029/2003jb002621
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发表时间：
2004-03
影响因子：
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通讯作者：
Y. Ogata
中科院分区：
文献类型：
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作者：
Y. Ogata
[1]将区域地震发生率建模为以往活动的函数，其具体形式分别基于时间和空间上的经验规律，如修正的Omori公式和余震面积与震级的Utsu-Seki标度定律。它的参数，包括余震衰减率的p值，因地而异，例如，主震周围位置的区域p值与对应的单个余震序列估计的p值相似。利用估计的时空模型对区域地震活动特征进行可视化。通过将该模型应用于1926-1995年期间日本及其周边地区的M≥5事件，证明了该模型的实用性。在模型的参数中，本文特别关注了表示余震生产力的修正Omori函数的归一化k值。在日本东北地区东海岸附近的广大地区，通过对历史强震记录的反演，在凸起边界周围获得高值。此外，该时空模型使我们能够识别出实际发生率与模型有系统偏差的异常时期和区域。这种相对于模型的异常（激活和静止）可以灵敏地揭示区域内应力的变化。我们试图将这种地震活动性的相对激活和降低与其他地方由于破裂或无声滑动而导致的库仑应力变化模式联系起来。例如，1995 - 1999年和2001年日本中部地震活动的异常（M≥2.5），分别可能是1995年神户断裂引起的库仑应力变化和2001年东海西部地区板块间地震滑动的结果。
[1] The regional occurrence rate of earthquakes is modeled as a function of previous activity, the specific form of which is based on empirical laws in time and space such as the modified Omori formula and the Utsu-Seki scaling law of aftershock area against magnitude, respectively. Its parameters, including the p-value of the aftershock decay rate, vary from place to place in such a way that, for example, the regional p-value at the locations around the main shock is similar to the one estimated from the corresponding individual aftershock sequence. The estimated space-time model is used to visualize features of the regional seismic activity. The utility is demonstrated by applying the model to the events of M ≥ 5 in and around Japan for the period 1926–1995. Among the parameters of the model, this paper is particularly concerned with the normalized K-value of the modified Omori function indicating the aftershock productivity. This takes high values around the boundaries of asperities that are estimated in the wide area off the East Coast of Tohoku District, Japan, by the inversion of historical strong motion seismograms. Furthermore, this space-time model enables us to identify the anomalous period and regions where the actual occurrence rates deviate systematically from the modeled one. Such an anomaly (activation and quiescence) relative to the model could sensitively reveal the change of stresses in the regions. We attempt to relate this relative activation and lowering of the seismicity to the pattern of Coulomb stress changes due to a rupture or silent slip elsewhere. For example, such anomalies seen in the seismic activity in the central Japan (M ≥ 2.5) during 1995–1999 and during 2001 are respectively likely the consequence of the Coulomb stress changes due to the 1995 Kobe rupture and the interplate aseismic slip during 2001 beneath the western Tokai region.