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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Seismic attenuation at Rabaul volcano, Papua New Guinea
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Seismic attenuation at Rabaul volcano, Papua New Guinea

机译：巴布亚新几内亚拉包尔火山的地震衰减

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摘要

The attenuation structure around Rabaul volcano, New Britain, Papua New Guinea, is studied using broadband records from a pair of sites, inside and outside of the Rabaul caldera complex, using regional earthquakes. Estimates of attenuation for P and S waves between 0.5 and 5 Hz indicate that near-surface rocks within the caldera complex are significantly more attenuative than outside the caldera. The average strength of this anomaly is defined in terms of t~*s ～ 0.2 s over and above the region outside the caldera (t~*s is the time integral of the inverse quality factor of attenuation, in this case along the path of a shear wave). This attenuation anomaly appears to be strongest at depth and to the south of the Kaivuna site in the northern part of the caldera complex. The ratio of attenuation estimates for P and S waves is δt~*_S/δt~*_P ≈ 2.7, indicating that intrinsic attenuation contributes significantly to the process of attenuation. No frequency dependence of the quality factor is resolved within this frequency band. Path-averaged lithospheric attenuation is estimated from S/P spectral ratios at both stations, yielding quality factors on average Q_β ～ 180, but possibly significantly lower around and below the volcano. Shear waves are observed along paths passing underneath the central southern caldera at depths greater than about 5 km, although they are strongly attenuated. This indicates that they have not passed through a large, extensively molten body.
机译：使用区域地震，利用拉包尔破火山口综合体内部和外部的一对站点的宽带记录，研究了新不列颠巴布亚新几内亚拉包尔火山周围的衰减结构。在0.5至5 Hz之间的P波和S波的衰减估计表明，破火山口内部的近地表岩石比破火山口外部的衰减要大得多。该异常的平均强度定义为破火山口外部区域之上和之上的t〜* s〜0.2 s（t〜* s是衰减的逆品质因数的时间积分，在这种情况下是沿衰减路径剪切波）。这种衰减异常在火山口复合体北部Kauvuna站点的南部和最深处似乎最强。 P波和S波的衰减估计值之比为δt〜* _S /δt〜* _P≈2.7，表明固有衰减对衰减过程有重要贡献。在该频带内没有解决品质因数的频率依赖性。根据两个站的S / P谱比估算路径平均岩石圈衰减，得出平均Q_β〜180的品质因数，但可能在火山周围和下方明显降低。尽管沿切变波强烈衰减，但沿穿过南部南部破火山口下方路径的深度大于约5 km。这表明它们尚未通过大的，广泛熔化的物体。

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