From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece
From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece
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从平静到动荡：希腊圣托里尼火山 20 年卫星大地测量
DOI：
10.1002/2014jb011540
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发表时间：
2015
期刊：
影响因子：
3.4
通讯作者：
Parks M
中科院分区：
文献类型：
--
作者：
Parks M
火山口形成的火山系统的动荡时期，其特征是地震活动和变形率增加。有些可能与最终的爆发活动有关，而另一些则随后恢复平静。在这里，我们使用了20年的干涉合成孔径雷达（干涉合成孔径雷达）和GPS测量圣托里尼火山的记录，以进一步了解火山口形成的火山在平静和动荡时期的大地测量信号，测量跨越了平静和缓慢沉降的阶段（1993-2010），随后是一个动荡的阶段（2011年1月至2012年4月），火山口范围内的通货膨胀和地震活动。1993-2010年的平均干涉合成孔径雷达速度图显示，在内亚卡梅尼岛的南半部，平均沉降率约为6毫米/年。这种下沉可以解释为1866-1870年熔岩流的热收缩和基底的负荷引起的松弛的组合。对于动荡时期，我们使用联合反演技术转换干涉合成孔径雷达测量从三个独立的卫星轨道和GPS观测从10个连续的站点到一个时间序列的地下体积变化。膨胀源的最佳位置与以前的研究一致，位于Nea Kameni北部，深度约为4公里。然而，时间序列揭示了两个不同的压力脉冲。第一个脉冲对应于浅部岩浆房的体积变化（ΔV）为（11.56 ± 0.14）× 106 m3，第二个脉冲对应于浅部岩浆房的体积变化（Δ V）为（9.73 ± 0.10）× 106 m3。这些脉冲的时间和微震观测之间的关系表明，这些脉冲可能是由两个单独的批次的岩浆供应到一个浅水库。我们没有发现任何证据表明两个脉冲之间的源位置的变化。两个脉冲结束时的体积变化率的下降和累积地震活动背后的变形信号的观察到的滞后，建议粘弹性响应。我们使用一个简单的模型表明，两个独立的脉冲侵入到一个浅岩浆房周围的粘弹性壳可以解释所观察到的时间变化的累积体积变化和地震活动在整个动荡时期。鉴于在这里观察到的大地测量信号和其他系统之间的相似性，这种粘弹性模型有可能用于了解其他破火山口系统的行为。
Periods of unrest at caldera‐forming volcanic systems characterized by increased rates of seismicity and deformation are well documented. Some can be linked to eventual eruptive activity, while others are followed by a return to quiescence. Here we use a 20 year record of interferometric synthetic aperture radar (InSAR) and GPS measurements from Santorini volcano to further our understanding of geodetic signals at a caldera‐forming volcano during the periods of both quiescence and unrest, with measurements spanning a phase of quiescence and slow subsidence (1993–2010), followed by a phase of unrest (January 2011 to April 2012) with caldera‐wide inflation and seismicity. Mean InSAR velocity maps from 1993–2010 indicate an average subsidence rate of ~6 mm/yr over the southern half of the intracaldera island Nea Kameni. This subsidence can be accounted for by a combination of thermal contraction of the 1866–1870 lava flows and load‐induced relaxation of the substrate. For the period of unrest, we use a joint inversion technique to convert InSAR measurements from three separate satellite tracks and GPS observations from 10 continuous sites into a time series of subsurface volume change. The optimal location of the inflating source is consistent with previous studies, situated north of Nea Kameni at a depth of ~4 km. However, the time series reveals two distinct pressure pulses. The first pulse corresponds to a volume change (ΔV) within the shallow magma chamber of (11.56 ± 0.14) × 106m3, and the second pulse has a ΔVof (9.73 ± 0.10) × 106m3. The relationship between the timing of these pulses and microseismicity observations suggests that these pulses may be driven by two separate batches of magma supplied to a shallow reservoir. We find no evidence suggesting a change in source location between the two pulses. The decline in the rates of volume change at the end of both pulses and the observed lag of the deformation signal behind cumulative seismicity, suggest a viscoelastic response. We use a simple model to show that two separate pulses of magma intruding into a shallow magma chamber surrounded by a viscoelastic shell can account for the observed temporal variation in cumulative volume change and seismicity throughout the period of unrest. Given the similarities between the geodetic signals observed here and at other systems, this viscoelastic model has potential use for understanding behavior at other caldera systems.