We analyze seismic waves excited by small Strombolian explosions to understand the source process of volcanic explosions. We deployed five broadband seismometers at only 100–300 m away from the active craters of Stromboli volcano, Italy. Moment tensor inversion of the entire seismic signals in the 0.05–0.2 Hz band locates the source at a depth of 170 and 150–200 m west/southwest of the crater where acoustic waves are excited. Contrary, the sources of seismic waves in the 0.2–0.5 and 0.5–1.0 Hz bands are excited almost at the explosion onset and are located close to the crater. We show for the first time that explosions are preceded of about 10–20 s by a small amplitude seismic phase. Semblance analysis shows that this phase is radiated from a depth of 170 m beneath the western part of the crater area. Our analysis indicates that the source moves about 50 m toward the active crater 10–20 s before the explosion occurs at the surface. At the explosion onset, the source moves back to the same location of the small preceding phase. These lateral migrations of the seismic source are estimated by moment tensor inversion and semblance analysis. We suggest that migration reflects the bending of the shallow feeding system toward northeast. Seismic waves are thus reflecting the history pressure generated by the rising of a gas-rich pocket in the very shallow portion of a magma mush and by the following restoring force occurring after the explosion.

中文翻译：

---

极近场宽带地震网推断斯特龙博利火山爆发期间的震源迁移

我们分析了小型斯特龙博利安爆炸激发的地震波，以了解火山爆炸的源过程。我们在距离意大利斯特龙博利火山的活火山口仅 100-300 m 处部署了五个宽带地震仪。0.05-0.2 Hz 频带内整个地震信号的矩张量反演将震源定位在 170 和 150-200 m 深度的火山口西/西南，在那里声波被激发。相反，0.2-0.5 和 0.5-1.0 Hz 波段的地震波源几乎在爆炸开始时被激发，并且位于火山口附近。我们首次表明，小振幅地震相在爆炸之前大约 10-20 秒。表观分析表明，该相是从火山口区域西部下方 170 m 的深度辐射的。我们的分析表明，在地表发生爆炸前 10-20 秒，震源向活动火山口移动了约 50 m。在爆炸开始时，源移回小前相的相同位置。震源的这些横向偏移是通过矩张量反演和相似性分析来估计的。我们认为迁移反映了浅层进食系统向东北方向的弯曲。因此，地震波反映了由岩浆糊非常浅的部分中富含气体的口袋上升以及爆炸后发生的后续恢复力所产生的历史压力。震源的这些横向偏移是通过矩张量反演和相似性分析来估计的。我们认为迁移反映了浅层进食系统向东北方向的弯曲。因此，地震波反映了由岩浆糊非常浅的部分中富含气体的口袋上升以及爆炸后发生的后续恢复力所产生的历史压力。震源的这些横向偏移是通过矩张量反演和相似性分析来估计的。我们认为迁移反映了浅层进食系统向东北方向的弯曲。因此，地震波反映了由岩浆糊非常浅的部分中富含气体的口袋上升以及爆炸后发生的后续恢复力所产生的历史压力。