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.

机械特性（即弹性模量和地震波速度）的显着降低以及非弹性衰减的增强通常与部分熔融岩石的区域有关。在本文中，我们提出了一种新机制，可显着降低波速并增强衰减。建议的机制考虑了热力学平衡时的固熔相变。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，从而根据克劳修斯-克拉珀龙方程改变热平衡。潜热（汇或源）通过传导-对流机制移走或移向界面，加热或冷却整个岩体，并导致能量损失和机械能耗散以及地震波衰减。我们使用简化的几何结构并推导出与移动的固体-熔体界面（Stefan 问题）相关的波速降低和衰减的解析解。我们证明，由于围绕热力学平衡的波浪引起的压力振荡而产生的潜热是能量耗散的有效机制，并导致机械性能（地震速度和衰减）的显着降低。当振荡周期接近与熔体夹杂物尺寸相关的传热时间尺度时，衰减最大。预测值与大尺度地震观测基本一致，表明地震波主要在地壳和地幔浅部衰减，并与可能存在熔体有关。