S wave coda Q from 3 to 20 Hz and P wave Q for foreshocks and aftershocks of the Petatlan Earthquake
S wave coda Q from 3 to 20 Hz and P wave Q for foreshocks and aftershocks of the Petatlan Earthquake
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3 至 20 Hz 的 S 波尾波 Q 和 Petatlan 地震前震和余震的 P 波 Q
DOI：
10.1029/jb095ib04p04787
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发表时间：
1990
影响因子：
--
通讯作者：
C. Helsley
中科院分区：
文献类型：
--
作者：
D. A. Novelo;Eduard Bero;C. Helsley
为了更好地了解地质非常年轻的俯冲带地壳上部在震源附近的力学性质变化和破裂过程，测定了1979年墨西哥佩塔特兰7.6级地震的部分前震和余震的S波尾波Qc=3~20 Hz和P波半脉宽Qp=6~12 Hz。为了限制样本范围，S尾波Qc的品质因子是从S发病后的前10个S中获得的。QC表现出强烈的时空和频率依赖性，在余震区的小前震部分，QC和QP在主震前显著低于主震后。四个不同地区的余震(n=1.3 2±0.0 3)和前震(n=1.4 3±0.0 7)的频度依赖关系n在QC(ƒ)=QOƒn中几乎是恒定的。仅在一个外周区域-站对中发现了一个显著不同的n(n=0.97±0.09)。我们的观察表明，Qc，也许还有频率依赖性n，对震源区的物理性质变化很敏感，可能有助于预测浅部俯冲带环境中的大地震。
In order to understand better the variations of mechanical properties close to the source and the failure process in the upper portion of the crust in a geologically very young subduction zone, the seismic S wave coda Qc from 3 to 20 Hz and P wave half pulse width Qp from 6 to 12 Hz were determined for selected foreshocks and aftershocks of the 1979 Petatlan, Mexico, Ms = 7.6 earthquake. To limit the region being sampled, the quality factor of S coda, Qc, was obtained from the first 10 s following the S onset. Qc exhibited a strong spatial, temporal, and frequency dependence, and in the small foreshock portion of the aftershock area, Qc and (to a lesser extent) Qp were significantly lower before the mainshock than afterward. The frequency dependence n, in Qc (ƒ) = Qo ƒn, was practically constant for aftershocks in four different regions (n = 1.32±0.03) and for foreshocks (n = 1.43±0.07). Only in one peripheral region-station pair did we find a significantly different n (n = 0.97±0.09). Our observations indicate that Qc, and perhaps the frequency dependence n, are sensitive to the physical property changes in the source region and might be useful as predictors of large earthquakes in a shallow subduction zone environment.