Geodetic observations during the 2009 eruption of Redoubt Volcano, Alaska
Geodetic observations during the 2009 eruption of Redoubt Volcano, Alaska
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DOI：
10.1016/j.jvolgeores.2012.04.021
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发表时间：
2013-06-01
影响因子：
2.9
通讯作者：
Kaufman, Alexander Max
中科院分区：
文献类型：
--
作者：
Grapenthin, Ronni;Freymueller, Jeffrey T.;Kaufman, Alexander Max
2009 年 3 月，距阿拉斯加安克雷奇西南约 160 公里的堡垒火山开始最近一次喷发。由 14 个基准组成的 GPS 活动网络记录了这次事件引起的变形，该网络是在上次喷发后于 1991 年建立的。该网络在 2001 年和 2008 年被部分重新占领，在此期间没有检测到火山变形。为了应对 2009 年 1 月开始的前兆骚乱，阿拉斯加火山观测站在 2009 年 3 月爆发活动爆发前几天，在四个活动基准点临时部署了连续记录 GPS 仪器。在火山喷发前的几个月内，唯一进行连续记录的 GPS 仪器是板块边界观测站 (PBO) AC17，位于火山顶峰东北约 28 公里处。该站的数据揭示了早在 2008 年 5 月就开始从火山径向向外的微妙运动，随着爆炸活动的开始而逆转。使用简单的分析模型，我们将前兆活动与海平面以下 13.50(17.33)(10.17) 公里处体积为 0.0194(0.0340)(0.0092) 16 km(3) 的点源侵入联系起来 (bsl，上标和下标是指 95% 水平下置信区间的上限和下限）。在爆炸阶段，约 0.05 >(0.028)(0.1) km(3)L 的岩浆从质心位于 9.17(15.17)(6.92) km bsl 的长椭球体中排出，长半轴长度为 4.50 >(1.25)(10.00) km，短半轴长度为0.475(>4.0)(0.3) 公里。推断喷发活动来自同一来源，体积减少了 0.0167(0.0228)(0.0106) km(3)。包括地震学和岩石学的观测结果，我们假设存在一个中地壳两个储层系统，其中来自 >20 km 的物质在约 13.5 km 深度流入，并在建议的球体中重新发现残余物质。混合物迁移到较浅的深度（2-4.5 km bsl）并在那里重新加热材料。当这些残留的岩浆喷发时，它被来自 7-11.5 公里深度的球状储层的物质所取代，这使得大地测量仪器无法检测到浅源。除了长期位移之外，我们还研究了亚日运动定位解决方案，发现大的短期定位偏移与大型爆炸事件相关。考虑到有利的卫星站几何形状，沿着各个卫星的天空轨迹绘制的相位残差中的尖峰可以与各个羽流相关，这可能用于火山监测。 (C) 2012 Elsevier B.V. 保留所有权利。
In March 2009 Redoubt Volcano, about 160 km to the SW of Anchorage, Alaska, began its most recent explosive eruption. Deformation induced by this event was recorded by a GPS campaign network consisting of 14 benchmarks, which had been established in 1991 after the previous eruption. The network was partially reoccupied in 2001 and 2008 and no volcanic deformation was detected during that period. In response to precursory unrest starting in January 2009, the Alaska Volcano Observatory temporarily deployed continuously recording GPS instruments at four of the campaign benchmarks only days before the onset of explosive activity in March 2009.The only GPS instrument recording continuously during the months prior to the eruption was the Plate Boundary Observatory (PBO) station AC17, about 28 km northeast of the volcano's summit. Data from this station reveals subtle motion radially outward from the volcano beginning as early as May 2008, which reversed with the onset of explosive activity.Using simple analytical models we link the precursory activity to a point source intrusion of 0.0194(0.0340)(0.0092) 16 km(3) in volume at 13.50(17.33)(10.17) km below sea level (bsl, superscripts and subscripts refer to upper and lower ends of confidence intervals at the 95% level). During the explosive phase about 0.05 >(0.028)(0.1) km(3)L of magma was evacuated from a prolate spheroid with its centroid at 9.17(15.17)(6.92) km bsl, a semimajor axis of 4.50 >(1.25)(10.00) km length and a semi-minor axis of 0.475(>4.0)(0.3) km. The effusive activity is inferred to come from the same source, decreasing in volume by 0.0167(0.0228)(0.0106) km(3).Including observations from seismology and petrology, we hypothesize a mid-crustal two reservoir system with material sourced from >20 km flowing in at about 13.5 km depth and rehearing residual material in the proposed spheroid. The mixture migrated to shallower depth (2-4.5 km bsl) and reheated material there. As this residual magma erupted, it was replaced by the material from the spheroidal reservoir at 7-11.5 km depth, which renders the shallow source undetectable for geodetic instruments.In addition to long term displacements we investigate sub-daily kinematic positioning solutions and find that large, short-term positioning offsets correlate with large explosive events. Spikes in phase residuals plotted along the sky tracks of individual satellites can be related to individual plumes given favorable satellitestation-geometry, which may be of use in volcano monitoring. (C) 2012 Elsevier B.V. All rights reserved.