Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations
Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations
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DOI：
10.1007/s00445-009-0296-4
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发表时间：
2009-06
影响因子：
3.5
通讯作者：
D. Dzurisin;M. Lisowski;C. Wicks
中科院分区：
文献类型：
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作者：
D. Dzurisin;M. Lisowski;C. Wicks
以南姐妹火山顶峰以西约6公里为中心的一大片区域于1997年9月开始抬升(根据本文讨论的模型估计的起始点)，并在2006年8月调查时仍在继续。自1992年8月以来，只要有可能，就用卫星雷达干涉测量(InSAR)测量地表位移，自2001年8月以来每年使用GPS和水准测量，自2001年5月以来使用连续GPS测量。InSAR的平均最大位移速率从1998-2001年的3-5厘米/年下降到2004-2006年的约1.4厘米/年。其他数据集显示了类似的模式，即地表隆起和伸展速率随着时间的推移而下降，但变形一直持续到2006年8月。我们对形变数据最适合的模型是位于地表以下4.9-5.4万公里的垂直的、延长的、球状的点压力源。2001-2006年间，源通货膨胀率呈指数级下降，年平均时间为5.3±1.1年。从1997年9月至2006年8月，污染源的净增加量为36.5-41.9×106立方米。2004年3月，在变形区下方发生了约300次小震(Mmax= 1.9)，未发现其他异常地震活动。如果像我们怀疑的那样，过去类似的变形事件大多是不会最终导致喷发的小侵入岩，那么可能就不会被注意到。
Uplift of a broad area centered ~6 km west of the summit of South Sister volcano started in September 1997 (onset estimated from model discussed in this paper) and was continuing when surveyed in August 2006. Surface displacements were measured whenever possible since August 1992 with satellite radar interferometry (InSAR), annually since August 2001 with GPS and leveling surveys, and with continuous GPS since May 2001. The average maximum displacement rate from InSAR decreased from 3–5 cm/yr during 1998–2001 to ~1.4 cm/yr during 2004–2006. The other datasets show a similar pattern, i.e., surface uplift and extension rates decreased over time but deformation continued through August 2006. Our best-fit model to the deformation data is a vertical, prolate, spheroidal point-pressure source located 4.9–5.4 km below the surface. The source inflation rate decreased exponentially during 2001–2006 with a 1/edecay time of 5.3 ± 1.1 years. The net increase in source volume from September 1997 to August 2006 was 36.5–41.9 x 106m3. A swarm of ~300 small (Mmax= 1.9) earthquakes occurred beneath the deforming area in March 2004; no other unusual seismicity has been noted. Similar deformation episodes in the past probably would have gone unnoticed if, as we suspect, most are small intrusions that do not culminate in eruptions.