Temporal change of Qp −1 in focal area of 1984 Western Nagano, Japan, Earthquake as derived from pulse width analysis
Temporal change of Qp −1 in focal area of 1984 Western Nagano, Japan, Earthquake as derived from pulse width analysis
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根据脉冲宽度分析得出的 1984 年日本长野西部地震震源区 Qp −1 的时间变化
DOI：
10.1029/jb092ib06p04846
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发表时间：
1987
影响因子：
--
通讯作者：
M. Ohtake
中科院分区：
文献类型：
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作者：
M. Ohtake
在初始P波脉宽加宽的基础上，研究了1984年日本中部长野西部M = 6.8级地震震源区Qp−1的时间变化。震源区的Qp−1在3.9 × 10−3到10.0 × 10−3之间，显著高于周边地区的2.8 × 10−3。然而，最大值不仅出现在主震之后，而且出现在主震后1天至2个月的时间内。在达到最大衰减后，焦点区域的Qp−1单调减小，接近周围区域的值。这种Qp−1变化的特征被新打开的裂缝逐渐被间隙流体饱和的模型成功地解释了。即使在主震发生前，震源区的Qp−1也远高于周边地区。地震前阶段的高衰减可能是M = 6.8地震前地震群的结果。然而，震源区的衰减强度增加仍有可能是长野西部地震的前兆。
On the basis of the pulse width broadening of initial P waves, temporal change of Qp−1 was investigated for the focal area of the 1984 western Nagano, central Japan earthquake of M = 6.8. Qp−1 in the focal area, ranging between 3.9 × 10−3 and 10.0 × 10−3, was significantly higher than that of the surrounding area, 2.8 × 10−3, throughout the 1.3-year postseismic stage that we examined. The highest value, however, appeared not just after the main shock but for the period from 1 day to 2 months following the main shock. After the maximum attenuation was attained, Qp−1 in the focal area monotonically decreased, approaching the value of the surrounding area. This characteristic feature of Qp−1 change is successfully accounted for by the model in which newly opened cracks are gradually saturated by interstitial fluid. Qp−1 of the focal area was much higher than the surrounding area even for the period prior to the main shock. The high attenuation of the preseismic stage is probably a consequence of the earthquake swarm which preceded the M = 6.8 earthquake. However, there remains a possibility that attenuation intensity in the focal area increased as a precursor to the western Nagano earthquake.