Surface deformation and stress interactions during the 2007-2010 sequence of earthquake, dyke intrusion and eruption in northern Tanzania
Surface deformation and stress interactions during the 2007-2010 sequence of earthquake, dyke intrusion and eruption in northern Tanzania
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DOI：
10.1093/gji/ggt226
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发表时间：
2013-10-01
影响因子：
2.8
通讯作者：
Hutchinson, Michael C.
中科院分区：
文献类型：
--
作者：
Biggs, Juliet;Chivers, Michael;Hutchinson, Michael C.
岩浆运动和断层滑动改变了周围地壳应力的大小和方向。对在空间和时间上聚集的一系列事件的观测提供了关于岩浆侵入、地震和火山爆发之间的触发机制和应力相互作用的信息。我们调查的同步和入侵后的应力变化与2007年Gelei堤坝入侵事件和随后的附近Oldonyo Lengai喷发。以前的研究产生了一个运动学模型的2007年6月至8月的序列，涉及类似1米的正断层上的滑动，然后侵入的7-10公里长的Gelei堤，浅地堑的崩溃和紧缩的Gelei岩浆房。紧接着，Oldoinyo Lengai火山（距离不到10公里）经历了一个持续数月的爆炸活动的新阶段。在这里，我们提出了新的大地测量观测涵盖Gelei和Oldoinyo Lengai在2008年9月至2010年。我们发现在格雷岩脉上方的地堑边界断层上有持续的滑动。Oldoinyo Lengai火山爆发时，一个4公里长的东西向堤坝侵入，紧接着火山顶正下方的一个浅源发生收缩。接下来，我们使用应力计算来研究将这些事件联系起来的一些假设。(1)在地表变形开始之前，一个足够深和窄的岩墙在大地测量上无法检测到，但它仍然可能产生足够的应力变化，触发正断层的滑动（即该序列可能是岩浆驱动的）。(2)岩墙尖端的应力足以克服正断层上持续滑动的影响，使岩墙向上传播到一个夹持区域。(3)Gelei序列会对Oldoinyo Lengai下方的洞穴产生显著的应力变化。这些静态应力计算使我们能够讨论整个序列中的动态应力，更深层次的岩浆变化和背景应力所起的作用，并对地震和火山灾害的应力触发产生影响。
Magma movement and fault slip alter the magnitude and orientation of the stress in the surrounding crust. Observations of a sequence of events clustered in space and time provide information about the triggering mechanism and stress interactions between magma intrusion, earthquakes and eruptions. We investigate the syn- and post-intrusion stress changes associated with the 2007 Gelei dyke intrusion episode and subsequent eruption of nearby Oldonyo Lengai. Previous studies produced a kinematic model of the 2007 June-August sequence involving similar to 1 m slip on a normal fault followed by the intrusion of the 7-10-km long Gelei dyke, collapse of a shallow graben and the deflation of the Gelei magma chamber. Immediately following this, the volcano Oldoinyo Lengai (< 10 km away) experienced a new phase of explosive activity lasting for several months. Here, we present new geodetic observations covering Gelei and Oldoinyo Lengai in 2008 September-2010. We show continued slip on graben-bounding faults above the Gelei dyke. The eruption of Oldoinyo Lengai was accompanied by the intrusion of a 4 km-long E-W-trending dyke followed by deflation of a shallow source directly below the summit of the volcano. Next, we use stress calculations to investigate a number of hypotheses linking these events. (1) Before the onset of surface deformation, a dyke sufficiently deep and narrow to be geodetically undetectable could still have produced sufficient stress changes to trigger slip on the normal fault (i.e. the sequence could have been magmatically driven). (2) Stresses at the dyke tip would have been sufficient to overcome the effect of continued slip on the normal fault, allowing the dyke to propagate upwards into a region of clamping. (3) The Gelei sequence would have produced a significant stress change on the chamber beneath Oldoinyo Lengai. These static stress calculations allow us to discuss the roles played by dynamic stress, deeper magmatic changes and background stresses throughout the sequence with implications for the stress triggering of both seismic and volcanic hazards.