Estimating volcanic deformation source parameters with a finite element inversion: The 2001-2002 unrest at Cotopaxi volcano, Ecuador
Estimating volcanic deformation source parameters with a finite element inversion: The 2001-2002 unrest at Cotopaxi volcano, Ecuador
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DOI：
10.1002/2014jb011731
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发表时间：
2015-03-01
影响因子：
3.9
通讯作者：
Mothes, Patricia
中科院分区：
文献类型：
--
作者：
Hickey, James;Gottsmann, Jo;Mothes, Patricia
尽管最后一次喷发发生在 1942 年，但在 2001 年至 2002 年间，观察到科托帕希的变形以及东北 (NE) 侧翼下方记录的地震活动。我们使用电子测距仪变形数据以及记录的地震活动模式来确定这次动乱事件的原因。为了求解最佳变形源参数，我们采用逆有限元 (FE) 模型来解释材料异质性和表面形貌。对于一系列源形状，模型集中在西南 (SW) 侧翼下方的浅水储层上。个体最佳拟合模型是一个小型扁圆状源，位于顶峰下方约 4-5 公里处，体积增加约 20x10(6)m(3)。该西南震源位置与东北地震活动位置形成对比。随后，进一步使用额外考虑温度相关粘弹性的有限元模型来同时协调变形和地震活动。弹性和粘性时间尺度的比较暗示了西南地区小型岩浆库的抗震加压。然后通过流体沿断层系统从西南向东北迁移的机制来解释东北向的地震活动。我们扩展我们的分析，进一步表明，如果未来的动乱危机伴随着变形源周围可测量的地震活动，这可能表明岩浆供应率更高，并且即将喷发的可能性增加。
Deformation at Cotopaxi was observed between 2001 and 2002 along with recorded seismicity beneath the northeast (NE) flank, despite the fact that the last eruption occurred in 1942. We use electronic distance meter deformation data along with the patterns of recorded seismicity to constrain the cause of this unrest episode. To solve for the optimum deformation source parameters we employ inverse finite element (FE) models that account for material heterogeneities and surface topography. For a range of source shapes the models converge on a shallow reservoir beneath the southwest (SW) flank. The individual best fit model is a small oblate-shaped source, approximately 4-5km beneath the summit, with a volume increase of roughly 20x10(6)m(3). This SW source location contrasts with the NE seismicity locations. Subsequently, further FE models that additionally account for temperature-dependent viscoelasticity are used to reconcile the deformation and seismicity simultaneously. Comparisons of elastic and viscous timescales allude to aseismic pressurization of a small magma reservoir in the SW. Seismicity in the NE is then explained through a mechanism of fluid migration from the SW to the NE along fault systems. We extend our analyses to further show that if future unrest crises are accompanied by measurable seismicity around the deformation source, this could indicate a higher magma supply rate and increased likelihood of a forthcoming eruption.