Effective seismic wave velocities and attenuation in partially molten rocks
Effective seismic wave velocities and attenuation in partially molten rocks
复制标题
DOI：
10.1016/j.epsl.2021.117117
复制
发表时间：
2021-10
影响因子：
5.3
通讯作者：
V. Lyakhovsky;E. Shalev;I. Kurzon;Wen-lu Zhu;L. Montési;N. Shapiro
中科院分区：
文献类型：
--
作者：
V. Lyakhovsky;E. Shalev;I. Kurzon;Wen-lu Zhu;L. Montési;N. Shapiro
力学性能的显著降低，即弹性模量和地震波速度，以及增强的非弹性衰减通常与部分熔融岩石区域有关。在本文中，我们提出了一个新的机制，负责显著降低波速和增强衰减。所建议的机制考虑了热力学平衡下的固-熔相变。根据克劳修斯-克拉珀龙方程，任何使系统脱离热力学平衡的压力变化都会导致凝固或熔化，从而改变热平衡。潜热（汇或源）通过传导-对流机制向界面转移或向界面转移，使整个岩体升温或降温，导致机械能的能量损失和耗散，使地震波衰减。我们使用简化的几何并推导出与移动固-熔界面（Stefan问题）相关的波速降低和衰减的解析解。我们证明了在热力学平衡附近由波浪诱导的压力振荡产生的潜热是一种有效的能量耗散机制，并导致机械性能（地震速度和衰减）的显著降低。当振荡周期接近与熔体夹杂物大小有关的传热时间尺度时，衰减幅度最大。预测值与大尺度地震学观测结果大致一致，表明地震波在地壳和地幔的浅层部分大多衰减，并与可能存在的熔体有关。
Significant reduction in mechanical properties, i.e., elastic moduli and seismic wave velocities, as well as enhanced inelastic attenuation is often associated with areas of partially molten rocks. In this paper we suggest a new mechanism responsible for significant reduction of wave velocity and enhanced attenuation. The suggested mechanism considers solid-melt phase transition at thermodynamic equilibrium. Any pressure change, that takes the system out of thermodynamic equilibrium, causes solidification or melting which modifies the heat balance according to the Clausius-Clapeyron equation. The latent heat (sink or source) is transferred away or towards the interface by conductive-advective mechanism, heating or cooling the entire rock mass, and leading to energy loss and dissipation of the mechanical energy and to seismic wave attenuation. We use simplified geometry and derive analytical solutions for wave velocity reduction and attenuation associated with a moving solid-melt interface (Stefan problem). We demonstrate that the latent heat generation due to wave-induced pressure oscillations around thermodynamic equilibrium is an efficient mechanism for energy dissipation and leads to significant reduction in mechanical properties (seismic velocities and attenuation). The highest attenuation occurs when the period of oscillation is close to the heat transfer time-scale associated with the size of melt inclusions. The predicted values are approximately in agreement with large scale seismological observations, showing that seismic waves are mostly attenuated within the shallow parts of Earth's crust and mantle, and are associated with possible presence of melt.