Long waves observed in the Kamchatka earthquake of November 4, 1952
Long waves observed in the Kamchatka earthquake of November 4, 1952
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DOI：
10.1029/jz063i003p00589
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发表时间：
1958-09
影响因子：
--
通讯作者：
H. Benioff
中科院分区：
文献类型：
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作者：
H. Benioff
传统地震仪的响应是，周期范围约为 5 至 20 秒的地震波以如此大的振幅写入地震图，以致无法观测到更长周期的波。因此，为了将观测范围扩大到更长的周期，我研制了一种电磁应变地震仪，其记录振镜周期为三分钟，等效面波摆放大系数为20。该地震仪组合投入使用以来发生的第一次大地震是1952年11月4日的堪察加地震。对这次地震余震序列的研究表明： 主震断层延伸约 1,000 公里，平均滑移约 15 英尺。图 1 显示了用新仪器记录的这次地震的部分地震图。该记录中最突出的事件是 G1 小波，它是没有垂直分量的水平偏振表面波。尽管G小波是洛夫波，但它的频率分量都位于色散曲线中基本平坦的部分，因此，小波的传播形状没有实质变化。因此，尽管由于对较高频率的吸收差异较大，G2 行进较长弧的持续时间已增加至 180 秒，但其形状并未改变。形状的明显变化是仪器响应特性的结果。对 G1 60 秒脉冲的响应与地面颗粒位移成正比，因为脉冲频率分量主要大于检流计频率。对于 G2，频率聚集在检流计的频率周围，因此总体响应大约与地面粒子速度成正比。因此，写在地震图上的 G2 脉冲是 G1 脉冲的一阶时间导数，表明两者形状相同。通过比较 G4-G2 和 G3-G1 的到达时间间隔，可以在地震图上测量 G 波绕地球完整一圈的传播时间。为 152.3 分钟 这对应于每秒 4.38 公里的表面速度，低于与 G 波一样深的剪切波的预期值。图2是包含G1和R1的地震图的一部分。
The responses of conventional seismographs are such that earthquake waves in the period range of about 5 to 20 seconds are written with such large amplitudes an the seismograms that longer period waves cannot be observed. Consequently, in order to increase the observable range to substantially longer periods, I developed an electromagnetic strain seismograph having a recording galvanometer of three minutes period and an equivalent pendulum magnification factor for surface waves of 20. The first great earthquake which has occurred since this seismograph combination was put into service was the Kamchatka shock of 1952, November 4. Studies of the aftershock sequence of this earthquake have indicated that in the principle shock faulting extended approximately 1,000 km with an average slip of about 15 feet. Figure 1 shows a portion of the seismogram of this earthquake written with the new instrument. The most prominent event on this record is the G1 wavelet, which is a horizontally polarized surface wave with no vertical component. Although the G wavelet is a Love wave, its frequency components · all lie in that part of the dispersion curve which is essentially flat, and, consequently, the wavelet propagates without substantial change of shape. Thus, although the duration of G2 which has traveled over the longer arc has been increased to 180 seconds owing to differentially greater absorption of the higher frequencies, its shape is not changed. The apparent change in shape is a result of the instrument response characteristics. The response to the 60-second pulse of G1 is proportional to ground particle displacement, since the pulse frequency components are mainly greater than the galvanometer frequency. With G2, the frequencies cluster about the frequency of the galvanometer, and the over-all response is thus approximately proportional to the ground particle velocity. The G2 pulse as written on the seismogram is thus the first time derivative of the G1 pulse, indicating identity of shape for the two. The time of travel for a complete circuit around the earth for the G wave was measured on the seismogram by comparing the arrival time intervals of G4–G2 and G3–G1 . It is 152.3 minute This corresponds to a surface velocity of 4.38 km per second, which is lower than the value to be expected for a shear wave which penetrates as deeply as the G wave. Figure 2 is a portion of the seismogram containing G1 and R1.