Lithological controls on igneous intrusion-induced ground deformation

Ground deformation commonly precedes volcanic eruptions, although its relationship to underlying intrusion networks is complex. We use 3D seismic reflection data to examine the link between a saucer-shaped sill and an overlying forced fold formed at the contemporaneous palaeosurface. Our results highlight a disparity in size between the sill and fold, which we attribute to accommodation of magma by overburden uplift and fluid expulsion from the host rock. Sill transgression occurred in response to plastic deformation of the host rock and did not produce seismically resolvable uplift. Inversion models of ground deformation should therefore acknowledge host rock behaviour during intrusion.

地面形变通常是火山喷发的前兆，但其与下伏侵入体网络之间的关联却较为复杂。我们采用三维地震反射数据（3D seismic reflection data），探究了碟状岩床（saucer-shaped sill）与同期古地表处形成的上覆强制褶皱（forced fold）之间的内在联系。研究结果显示，岩床与褶皱的尺寸存在显著差异，我们将该差异归因于上覆层抬升以容纳岩浆，以及围岩发生流体逸出作用。岩床扩展作用的发生是对围岩塑性变形的响应，并未产生地震可分辨的抬升现象。因此，地面形变反演模型应当纳入侵入过程中围岩的行为特性。