Fragmentation dynamics can be described by the size distribution of the fragments generated during an explosion. We approach the problem of magma fragmentation during a Strombolian explosion using the grain size distribution (GSD) of a ballistically emplaced lapilli-and-bomb deposit. We present a novel method of collecting juvenile fragments landing in a well-defined near-vent zone (around 50 m from the source). The method uses four plastic sheets (tarpaulins or tarps) deployed below the SW crater rim of Stromboli volcano (Aeolian Islands, Italy). Due to the vicinity of the collection site to the vent, the fragments were still hot when they landed and created a map of melt holes on the sheets. This map was processed to calculate cumulative fragment size distributions (FSD) and grain size distributions (GSD). The cumulative FSD (number based) and GSD (mass-based) are best described by unique power laws with fractal dimensions of 1.40 and 2.03, respectively, testifying to the fractal nature of fragmentation. The fractal dimension is consistent with low energy fragmentation of a brittle material. This method represents a new way of measuring fragmentation dynamics and classifying volcanic eruptions according to their fragmentation energy.

碎片动力学可以通过爆炸过程中产生的碎片的大小分布来描述。我们使用弹道放置的炸弹和炸弹沉积物的粒度分布（GSD）来处理在斯特伦波斯爆发期间的岩浆破碎问题。我们提出了一种新颖的方法来收集降落在一个明确的近通风区（距源头约50 m）的少年碎片。该方法使用部署在斯特龙博利火山（意大利风神群岛）的西南火山口边缘下方的四个塑料板（篷布或防水布）。由于排气口的收集地点附近，碎片落下时仍很热，并在板上形成了熔洞图。处理该图以计算累积碎片尺寸分布（FSD）和晶粒尺寸分布（GSD）。累积FSD（基于数量）和GSD（基于质量）最好用分形维数分别为1.40和2.03的唯一幂定律来描述，这证明了碎片的分形性质。分形维数与脆性材料的低能碎裂一致。该方法代表了一种测量碎裂动力学并根据碎裂能量对火山喷发进行分类的新方法。