Seismic source spectrum of microearthquakes
Seismic source spectrum of microearthquakes
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DOI：
10.1785/bssa0820062391
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发表时间：
1992-12
影响因子：
3
通讯作者：
Y. Iio
中科院分区：
文献类型：
--
作者：
Y. Iio
本文利用一个优良硬岩场地的局部记录，研究了地震矩在1014 ~ 1018达因厘米之间的微地震的震源谱。现场附近的P波速度估计约为6公里/秒，甚至直接低于地面。滞弹性衰减的影响被认为非常小，因为在焦距大于10公里的地震图中检测到的主要频率大于100赫兹。观测到许多S-P时间小于0.6秒的地震图。在这项研究中使用的第一个周期的P波速度地震记录。第一个周期之后的波形可能在场地附近形成，因为它们的周期对于具有不同震源过程的地震完全相同。在估计的位移源谱的高频部分中，衰减的斜率具有远大于2的值。微震的震源过程被假定为非常缓慢和平滑的。
The seismic source spectra of microearthquakes having seismic moments between 1014 and 1018 dyne cm were investigated by using local recordings from an excellent hard-rock site. The P-wave velocity near the site was estimated as about 6 km/sec, even immediately below the ground surface. The effect of anelastic attenuation was thought to be very small, since predominant frequencies of greater than 100 Hz were detected in seismograms recorded at focal distances greater 10 km. Many seismograms with S-P times of less than 0.6 sec were observed. The first cycle of the P-wave velocity seismogram was used in this study. The waveforms after the first cycle are likely formed near the site, since their periods are exactly the same for earthquakes that have different source processes. In the high-frequency portion of the estimated displacement source spectra, the slopes of the fall-off have values much greater than 2. The source process of microearthquakes is assumed to be very slow and smooth.