Multiscale fracturing as a key to forecasting volcanic eruptions
Multiscale fracturing as a key to forecasting volcanic eruptions
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DOI：
10.1016/s0377-0273(03)00117-3
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发表时间：
2003-07-20
影响因子：
2.9
通讯作者：
Kilburn, CRJ
中科院分区：
文献类型：
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作者：
Kilburn, CRJ
在长时间休眠后重新苏醒的火山中，最后接近喷发（类似于1-10天）的特征通常是地震活动的加速率。观察到的模式与断层的缓慢延伸是一致的，断层继续增长，直到它们连接到预先存在的一系列近垂直裂缝，从而为岩浆到达地表开辟了一条新的途径。这里研究的缓慢伸展速率假设重力加载和岩浆超压在围岩中产生波动的应力场。波动是由于监测仪器无法检测到的小裂纹的间歇性增长。检测到的事件的速率，然后确定的频率与周围的宏观故障的尖端应变能的集中变得足够大，允许故障扩展。该模型预计振荡的地震事件率的平均趋势，随着时间的推移加速，并确定了峰值事件率的增加率作为一个关键指标的方法喷发。结果是一致的，与早期的经验分析地震前兆，并适用于1991年的皮纳图博山，菲律宾，和苏弗里埃山，蒙特塞拉特，在1995年安山岩喷发前的数据，他们建议，对于这样的火山，可靠的预测岩浆活动可能最终是可行的顺序喷发前几天。(C)2003 Elsevier Science B. V.保留所有权利。
Among volcanoes reawakening after long repose intervals, the final approach to eruption (similar to 1-10 days) is usually characterised by accelerating rates of seismicity. The observed patterns are consistent with the slow extension of faults, which continue to grow until they connect a pre-existing array of subvertical fractures and so open a new pathway for magma to reach the surface. Rates of slow extension are here investigated assuming that gravitational loading and magma overpressure create a fluctuating stress field in the country rock. Fluctuations are due to the intermittent growth of small cracks that cannot be detected by monitoring instruments. The rate of detected events is then determined by the frequency with which the concentration of strain energy around the tips of macroscopic faults becomes large enough to permit fault extension. The model anticipates oscillations in seismic event rate about a mean trend that accelerates with time, and identifies the rate of increase in peak event rate as a key indicator of the approach to eruption. The results are consistent with earlier empirical analyses of seismic precursors and, applied to data before the andesitic eruptions of Mt Pinatubo, Philippines, in 1991, and of Soufriere Hills, Montserrat, in 1995, they suggest that, for such volcanoes, reliable forecasts of magmatic activity might eventually be feasible on the order of days before eruption. (C) 2003 Elsevier Science B.V. All rights reserved.