Very Long Period (VLP) signals with periods longer than 2 s may occur during eruptive or quiet phases at volcanoes of all types (shield and stratovolcanoes with calderas, as well as other stratovolcanoes) and are inherently connected to fluid movement within the plumbing system. This is supported by observations at several volcanoes that indicate a correlation between gas emissions and VLPs, as well as deformation episodes due to melt accumulation and migration that are followed by the occurrence of VLPs. Moment tensors of VLPs are usually characterized by large volumetric components of either positive or negative sign along with possibly the presence of single forces that may result from the exchange of linear momentum between the seismic source and the Earth. VLPs may occur during a variety of volcanological processes such as caldera collapse, phreatic eruptions, vulcanian eruptions, strombolian activity, and rockfalls at lava lakes. Physical mechanisms that can generate VLPs include the inflation and deflation of magma chambers and cracks, the movement of gas slugs through conduits, and the restoration of gravitational equilibrium in the plumbing system after explosive degassing or rockfalls in lava lakes. Our understanding of VLPs is expected to greatly improve in the future by the use of new instrumentation, such as Distributed Acoustic Sensing, that will provide a much denser temporal and spatial sampling of the seismic wavefield. This vast quantity of data will then require time efficient and objective processing that can be achieved through the use of machine learning algorithms.

周期超过 2 秒的甚长周期 (VLP) 信号可能会在所有类型的火山（盾构火山和带有破火山口的成层火山，以及其他成层火山）的喷发或安静阶段出现，并且与管道系统内的流体运动有着内在的联系。对几座火山的观测结果支持了这一点，这些观测表明气体排放与 VLP 之间存在相关性，以及由于 VLP 出现后熔体积累和迁移导致的变形事件。 VLP 的力矩张量通常具有正号或负号的大体积分量的特征，并且可能存在由震源和地球之间的线性动量交换产生的单一力。 VLP 可能发生在各种火山过程中，例如火山口塌陷、潜水喷发、火山喷发、斯特龙博利活动和熔岩湖落石。产生 VLP 的物理机制包括岩浆室和裂缝的膨胀和收缩、气段塞通过管道的运动，以及熔岩湖中爆炸脱气或落石后管道系统中重力平衡的恢复。通过使用分布式声学传感等新仪器，我们对 VLP 的理解预计将在未来大大提高，这将提供更密集的地震波场时空采样。如此大量的数据将需要时间高效且客观的处理，这可以通过使用机器学习算法来实现。