Stress drops and radiated seismic energies of microearthquakes in a South African gold mine
Stress drops and radiated seismic energies of microearthquakes in a South African gold mine
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DOI：
10.1029/2006jb004553
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发表时间：
2007-03
影响因子：
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通讯作者：
Takuji Yamada;J. Mori;S. Ide;R. Abercrombie;H. Kawakata;M. Nakatani;Y. Iio;H. Ogasawara
中科院分区：
文献类型：
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作者：
Takuji Yamada;J. Mori;S. Ide;R. Abercrombie;H. Kawakata;M. Nakatani;Y. Iio;H. Ogasawara
[1]我们估计了南非金矿20次微地震（0.0 < MW < 1.3）的应力降和辐射地震能量，以研究它们的破裂特征及其与大地震的尺度关系。我们分析了在震源深度2650 m的200 m范围内以高采样率（15 kHz）记录的钻孔加速度计的地震记录。波形数据具有很高的信噪比，所有台站均未观测到明显的后期相位。假设Boatwright（1978）的omega平方模型，从速度地震谱中估计出拐角频率和非弹性衰减Q的质量因子。我们还从波形反演中研究了双偶解的矩张量和体积分量。Madariaga（1976）模型计算的20次地震的静应力降范围为3.2 ~ 88 MPa，标度能量（= ER/Mo，辐射能ER与地震矩Mo之比）范围为4.2 × 10−6 ~ 1.1 × 10−4。我们发现，所分析的地震的静态应力降和标度能量与大地震的值相当。结果表明，这些微地震的动态破裂过程与大地震的动态破裂过程相似。
[1] We estimate stress drops and radiated seismic energies of 20 microearthquakes (0.0 < MW < 1.3) in a South African gold mine to investigate their rupture characteristics and scaling relationships to large earthquakes. We analyze seismograms of borehole accelerometers recorded with high sampling rate (15 kHz) within 200 m of the hypocenters at the depth of 2650 m. The waveform data have very high signal-to-noise ratio and no significant later phases are observed at all stations. Corner frequencies and quality factors of the anelastic attenuation Q are estimated from spectra of velocity seismograms by assuming the omega squared model of Boatwright (1978). We also investigate moment tensors for double couple solutions and volumetric components from the waveform inversion. Static stress drops of the 20 earthquakes calculated from the model of Madariaga (1976) are from 3.2 to 88 MPa and scaled energies (= ER/Mo; the ratio of the radiated energy ER to the seismic moment Mo) are from 4.2 × 10−6 to 1.1 × 10−4. We find that both the static stress drops and the scaled energies of the analyzed earthquakes are comparable to those values of larger earthquakes. Our results indicate that the dynamic rupture processes of these microearthquakes are similar to those of larger earthquakes.