Symmetry-breaking instabilities in high- pressure phase transformation produce the counterintuitive phenomenon of “volume collapse” producing only shear radiation, with little, or no, volumetric component, even under conditions of full isotropy, and explain the mystery of the long-standing observations in deep-focus earthquakes (400-700 km). Due to instability, at a critical “nucleation pressure”, an arbitrarily small densified region, in the shape of a “pancake-like” flattened ellipsoidal Eshelby inclusion, grows self-similarly as a “lacuna” (zero particle velocity) with the phase transformation occurring under conditions of equilibrium in uniform strain/stress and at constant potential energy (at the vanishing of the M integral, when the radius-expanding driving force $p{\epsilon }_{kk}^{*}$ overcomes the radius-shrinking self-force). The symmetry-breaking flattened shape favors minimization of the energy needed for the boundary to grow large, while for the accommodation of the large collapsing volume in the very thin inclusion deviatoric stresses are developed to avoid openings and overlaps. It is shown that, if an arbitrarily small flattened densified region is generated planarly, and the pressure exceeds the critical nucleation value, then it will necessarily produce a shear seismic source, with little or no, volumetric component, nucleated and driven to propagate by the pressure. The ellipsoid of phase change forms in the direction that minimizes the interaction energy with the pre-stress field in the mantle and will be close to the direction of max shear pre-stress. The obtained stress/deformation fields of a densified 2D flattened elliptical inclusion constitute a new defect that models the “anticrack” in geophysics and densified shear bands. The instability analysis can be extended to the nucleation and growth of the phase transition from water to a solid ice phase under high pressure, with the discovered instabilities providing insight to other phenomena of dynamic phase transformations, such as failure waves, amorphization, planetary impacts, etc.

高压相变中破坏对称的不稳定性会产生“体积崩溃”的反直觉现象，即使在完全各向同性的条件下，也只会产生剪切辐射，几乎没有或根本没有体积分量，这也解释了长期观测的奥秘在深层地震（400-700公里）中。由于不稳定性，在临界“成核压力”下，任意细小的致密区域呈“薄饼状”扁平椭圆形埃舍尔比夹杂物的形状，自相生长为类似“空隙”（零粒子速度）的相，在均匀的应变/应力和恒定的势能（在M积分消失时，当半径扩展驱动力时）下发生的相变$p{\epsilon }_{ķķ}^{*}$克服了半径收缩的自力）。破坏对称的扁平形状有利于使边界增大所需的能量最小化，同时为了在非常薄的夹杂物中容纳较大的塌陷体积，开发了偏应力以避免开孔和重叠。结果表明，如果在平面上产生一个任意小的扁平致密化区域，并且压力超过临界成核值，那么它将必然产生一个剪切地震源，该地震源几乎没有或根本没有体积成分，并由核形成并被驱动传播。压力。相变的椭球形成的方向使得与地幔中的预应力场的相互作用能最小，并且将接近最大剪切预应力的方向。致密的二维扁平化椭圆形夹杂物所获得的应力/变形场构成了一种新的缺陷，该缺陷模拟了地球物理学中的“抗裂”和致密的剪切带。不稳定性分析可以扩展到高压下从水到固态冰相的相变的成核和生长，发现的不稳定性可以提供对动态相变其他现象的洞察力，例如破坏波，非晶化，行星撞击，等等。