Abstract Volcanoes emit volcanic gas during various types of activity. In the case of andesitic and dacitic volcanoes the high viscosity of silicic magma inhibits the release of volatiles. This increases the possibility that gas escape will occur explosively. The explosive emission of volatile constituents, presented in magmas, generates the seismic signals which may give information about the process of degassing at different stages of eruption. Transition between the eruptive episodes of lava dome-building at andesitic volcanoes represents the transition from passive degassing of the final stage of one episode to pre-extrusion degassing of the next episode. In this article we use the seismic parameters of volcanic explosions, volcanic tremor and micro-explosions, recorded at Volcan de Colima during August–September 2004, to describe the process of transition from passive to pre-extrusion degassing from episode 2 (May 2001–September 2004) to episode 3 (30 September 2004–January 2007). Variations in the tilt changes allowed us to identify three periods in development of this transition: period of passive degassing at the final stage of episode 2 (until 6 September) and two periods of pre-extrusive degassing at the initial stage of episode 3 defined by processes of inflation and deflation of volcanic structure from 6 to 30 September. Intensity of degassing of magma, expressed in the energy of volcanic explosions, decreased during transition from passive to pre-extrusive stages. During pre-extrusion periods of inflation and deflation of volcanic structure the depths of explosive events became shallower. Period of deflation was characterized also by a dominance of degassing processes occurring within the permeable cap of ascending magma and generating volcanic tremors and swarms of micro-earthquakes. Comparison of degassing of magma during pre-extrusive period and co-extrusive and post-extrusive periods showed the similarity in intensity of degassing of magma during the pre-extrusive and co-extrusive periods but a sharp increase in degassing intensity during the post-extrusive period of lava dome destruction with large explosions. It was shown also minor intensity of degassing processes just preceding the beginning of the lava dome building comparing with intensity of degassing processes just preceding the beginning of the lava dome destruction with great explosions.

中文翻译：

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从地震信号和倾斜变化得出的熔岩穹顶喷发前上升安山岩浆从被动到挤压前脱气的转变：墨西哥科利马火山，2004 年 8 月至 9 月

摘要 火山在各种活动中都会释放火山气体。在安山质和英安质火山的情况下，硅质岩浆的高粘度抑制了挥发物的释放。这增加了气体逸出爆炸性发生的可能性。岩浆中挥发性成分的爆炸性排放产生地震信号，这些信号可能提供有关喷发不同阶段脱气过程的信息。安山岩火山熔岩穹顶喷发阶段之间的过渡代表了从一个阶段最后阶段的被动脱气到下一个阶段的挤压前脱气的过渡。在本文中，我们使用了 2004 年 8 月至 9 月在科利马火山记录的火山爆发、火山震颤和微爆炸的地震参数，描述从第 2 集（2001 年 5 月至 2004 年 9 月）到第 3 集（2004 年 9 月 30 日至 2007 年 1 月）从被动脱气到挤出前脱气的过渡过程。倾斜变化的变化使我们能够确定这种转变发展的三个时期：第 2 集最后阶段（直到 9 月 6 日）的被动脱气时期和第 3 集初始阶段的两个预挤出脱气时期，定义为9 月 6 日至 30 日火山结构的膨胀和收缩过程。以火山爆发的能量表示的岩浆脱气强度在从被动到喷出前阶段的过渡期间降低。在火山结构膨胀和收缩的挤压前时期，爆炸事件的深度变浅。通货紧缩时期的特征还在于，在上升的岩浆的可渗透盖内发生的脱气过程占主导地位，并产生火山震颤和成群的微地震。前喷出期与共喷出期和后喷出期岩浆脱气的对比表明，前喷出期和共喷期岩浆脱气强度相似，但后喷出期脱气强度急剧增加。熔岩穹顶被大爆炸破坏的时期。与刚开始熔岩穹顶破坏和大爆炸之前的脱气过程强度相比，还显示出在熔岩穹顶建造开始之前的脱气过程强度较小。