Abstract Volcano-seismic signatures are the convolution of source and path effects. The source signature provides important information about the dynamic rock deformation and fluid resonance processes within the volcano, but path effects are the result of the volcanic plumbing, the edifice physical conditions, and the complex geological structure. Complicating the inversion of seismic data further, is the influence of fluid properties. Here, we use ultrasonic experiments to understand the effect of variable fluid viscosity and bulk modulus on P-wave attenuation and velocity for volcanic rocks from White Island volcano (Whakaari), New Zealand. Our experimental conditions for high-porosity ash tuff and low-porosity lava resemble shallow and deep volcano facies respectively. P-wave velocity, Vp, and quality factor, Qp, increase with the viscosity and bulk modulus of the saturating fluid and decrease with porosity and fracture volume. Tuffs are highly sensitive to saturating fluid, with variations in Vp of up to 67% and Qp of 383%. Vp and Qp in fractured lavas are slightly less sensitive to fluids (24% and 296% respectively), but Vp can be used to identify lithology for these tuff vs. lavas. Comparison of the experimental data with rock physics models suggests that squirt flow is the dominant attenuation mechanism for viscosities greater than that of water, while scattering losses may be important in gas saturated rocks. Our results have significant implications for the interpretation of seismic tomography studies and for volcano hazard monitoring based on the characteristics of detected seismicity.

中文翻译：

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流体类型对火山岩弹性波速度和衰减的影响

摘要 火山地震特征是震源效应和路径效应的卷积。源特征提供了关于火山内部动态岩石变形和流体共振过程的重要信息，但路径效应​​是火山管道、建筑物物理条件和复杂地质结构的结果。流体性质的影响使地震数据的反演进一步复杂化。在这里，我们使用超声波实验来了解可变流体粘度和体积模量对新西兰怀特岛火山 (Whakaari) 火山岩的 P 波衰减和速度的影响。我们对高孔隙度灰凝灰岩和低孔隙度熔岩的实验条件分别类似于浅火山相和深火山相。P 波速度 Vp 和品质因数 Qp，随饱和流体的粘度和体积模量增加，随孔隙度和裂缝体积而减小。凝灰岩对饱和流体高度敏感，Vp 变化高达 67%，Qp 变化高达 383%。破裂熔岩中的 Vp 和 Qp 对流体的敏感性稍低（分别为 24% 和 296%），但 Vp 可用于识别这些凝灰岩与熔岩的岩性。将实验数据与岩石物理模型进行比较表明，喷射流是粘度大于水的主要衰减机制，而散射损失在气体饱和岩石中可能很重要。我们的结果对地震层析成像研究的解释和基于检测到的地震活动特征的火山灾害监测具有重要意义。