Anomalous emissions of SO2 during the recent eruption of Santa Ana volcano, El Salvador, Central America
Anomalous emissions of SO2 during the recent eruption of Santa Ana volcano, El Salvador, Central America
复制标题
DOI：
10.1007/s00024-007-0276-6
复制
发表时间：
2007-12-01
影响因子：
2
通讯作者：
Galle, Bo
中科院分区：
文献类型：
--
作者：
Olmos, Rodolfo;Barrancos, Jose;Galle, Bo
位于中美洲萨尔瓦多西部的圣安娜火山于2005年10月1日上午8点05分（当地时间）发生潜水喷发，距离上次喷发已有101年。然而，在过去的一百年里，这座火山出现了平静的脱气时期，火山活动和火山口内的酸性湖。本文介绍了频繁的测量结果的SO2脱气使用MiniDOAS（差分光学吸收光谱）系统和火山喷发前，期间和喷发后的地震活动的比较。在喷发的前九天，每小时和之后的每天都对二氧化硫通量进行车辆测量。报告的时间段为2005年8月至12月。三个时期的脱气区分：喷发前，喷发，喷发后的时期。圣安娜火山的剧烈活动始于2005年7月。在喷发前的4306和5154吨/天的二氧化硫通量分别记录在2005年10月24日和9月9日。这些数值与10月1日喷发后记录的数值（上午10：01时为2925吨/天）的数量级相同。每小时测量的SO2通量在第一个9天后的主要喷发事件表明，爆炸之前的SO2通量的增加，这一参数达到峰值后，爆炸发生。这种行为表明，在爆炸前，岩浆室内发生了越来越多的出溶岩浆气体的积累，增加了压力，直到爆炸点。在整个采样期间，观测到SO2通量与RSAM（真实的时间地震振幅测量）之间的相关性。在整个研究期间观察到的SO2和RSAM值的周期性波动。解释这些波动的一个可能机制是，岩浆房内的对流循环可以周期性地将新鲜岩浆带到较浅的水平，随着这批岩浆降低其气体含量，允许增加脱气，然后减少脱气，变得更致密，并下沉以给新的岩浆脉冲提供空间。这些结果表明，SO2通量的测量可以提供重要的预警信号，在活火山爆发活动的到来。
Santa Ana volcano in western El Salvador, Central America, had a phreatic eruption at 8:05 am (local time) on October 1, 2005, 101 years after its last eruption. However, during the last one hundred years this volcano has presented periods of quiet degassing with fumarolic activity and an acidic lake within its crater. This paper presents results of frequent measurements of SO2 degassing using the MiniDOAS (Differential Optical Absorption Spectroscopy) system and a comparison with the volcanic seismicity prior to the eruption, during, and after the eruption. Vehicle measurements of SO2 flux were taken every hour during the first nine days of the eruption and daily after that. The period of time reported here is from August to December, 2005. Three periods of degassing are distinguished: pre-eruptive, eruptive, and post-eruptive periods. The intense activity at Santa Ana volcano started in July 2005. During the pre-eruptive period up to 4306 and 5154 ton/day of SO2 flux were recorded on October 24 and September 9, 2005, respectively. These values were of the same order of magnitude as the recorded values just after the October 1(st) eruption (2925 ton/day at 10: 01 am). Hourly measurements of SO2 flux taken during the first nine days after the main eruptive event indicate that explosions are preceded by an increase in SO2 flux and that this parameter reaches a peak after the explosion took place. This behavior suggests that increasing accumulation of exsolved magmatic gases occurs within the magmatic chamber before the explosions, increasing the pressure until the point of explosion. A correlation between SO2 fluxes and RSAM (Real Time Seismic Amplitude Measurements) is observed during the complete sampling period. Periodic fluctuations in the SO2 and RSAM values during the entire study period are observed. One possible mechanism explaining these fluctuations it that convective circulation within the magmatic chamber can bring fresh magma periodically to shallow levels, allowing increasing degasification and then decreasing degasification as the batch of magma lowers its gas content, becomes denser, and sinks to give space to a new magma pulse. These results illustrate that the measurements of SO2 flux can provide important warning signals for incoming explosive activity in active volcanoes.