Seismicity and deformation induced by magma accumulation at three basaltic volcanoes
Seismicity and deformation induced by magma accumulation at three basaltic volcanoes
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三座玄武岩火山岩浆堆积引起的地震活动和变形
DOI：
10.1029/2008jb005937
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发表时间：
2008
影响因子：
--
通讯作者：
P. Okubo
中科院分区：
文献类型：
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作者：
O. Lengliné;D. Marsan;J. Got;V. Pinel;V. Pinel;V. Ferrazzini;P. Okubo
本文分析了基拉韦厄火山、莫纳罗亚火山、皮顿德拉富尔奈斯火山三座玄武岩火山在岩浆聚集阶段的火山构造地震活动和变形演化。我们观察到，在岩浆聚集时期，所研究的三座火山的VT地震活动呈现出加速演化的趋势。与此同时，基拉韦厄火山和莫纳罗亚火山山顶记录的变形率并没有加速，而是趋于衰减。为了解释这些观察结果，我们提出了一个物理模型来描述岩浆积聚到储层中所产生的压力演化。这种压力的变化然后被用来建立一个简单的破坏模型，其中的破坏事件相当于地震。该模型导致在堆积阶段VT活度呈指数增长，变形速率呈指数衰减。这种指数模型可以很好地拟合地震活动性和变形数据。由地震活动性指数增长推导出的时间常数与岩浆聚集模型预测的时间常数一致。因此，这种VT活动可以直接表明岩浆在深处积聚，因此可以被视为一种长期的前兆现象，至少对于研究的三座玄武岩火山来说是这样。不幸的是，它不能预测未来爆发的开始，因为模型中没有发散点（即临界时间）。
We analyzed the evolution of volcano-tectonic (VT) seismicity and deformation at three basaltic volcanoes (Kilauea, Mauna Loa, Piton de la Fournaise) during phases of magma accumulation. We observed that the VT earthquake activity displays an accelerating evolution at the three studied volcanoes during the time of magma accumulation. At the same times, deformation rates recorded at the summit of Kilauea and Mauna Loa volcanoes were not accelerating but rather tend to decay. To interpret these observations, we propose a physical model describing the evolution of pressure produced by the accumulation of magma into a reservoir. This variation of pressure is then used to force a simple model of damage, where damage episodes are equivalent to earthquakes. This model leads to an exponential increase of the VT activity and to an exponential decay of the deformation rate during accumulation phases. Seismicity and deformation data are well fitted by such an exponential model. The time constant, deduced from the exponential increase of the seismicity, is in agreement with the time constant predicted by the model of magma accumulation. This VT activity can thus be a direct indication of the accumulation of magma at depth, and therefore can be seen as a long-term precursory phenomenon, at least for the three studied basaltic volcanoes. Unfortunately, it does not allow the prediction of the onset of future eruptions, as no diverging point (i.e., critical time) is present in the model.