Interpretation of very long period tremors at Ambrym volcano, Vanuatu, as quasi‐static displacement field related to two distinct magmatic sources
Interpretation of very long period tremors at Ambrym volcano, Vanuatu, as quasi‐static displacement field related to two distinct magmatic sources
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DOI：
10.1029/2004gl021968
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发表时间：
2005-03
影响因子：
5.2
通讯作者：
D. Legrand;D. Rouland;M. Frogneux;R. Carniel;D. Charley;G. Roult;C. Robin
中科院分区：
文献类型：
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作者：
D. Legrand;D. Rouland;M. Frogneux;R. Carniel;D. Charley;G. Roult;C. Robin
2000年7月至11月，在瓦努阿图Ambrym的西南斜坡上部署了一台三分量宽带地震仪（STS-2），Ambrym是一座大型破火山口，有两个持续的熔岩湖。极化良好的甚长周期地震（18- 22秒; VLPT）连续发生，而其他周期为9秒、6- 7秒、5秒、2.3- 2.7秒、1.95秒和1秒的地震信号是间歇性的。VLPT信号显示两个明显不同的方向指向破火山口。极化方向表明有两个来源：第一个，也是最活跃的，与1986年火山熔岩流爆发的区域相吻合，位于火山口的中部到东部。第二个对应于由复杂的Marum火山中心和Benbow锥形成的活动带，位于凹陷构造的西部。深度估计在2.7-2.9公里之间，相对于海平面。VLPT被解释为两个非破坏性源的准静态位移场。它们表明，火山口东底下持续不断的岩浆活动，尽管在这一地区没有观察到火山活动，但更明显，但不太活跃，对应于熔岩湖。这些数据也证实了Ambrym破火山口复杂的内部结构，这是由地质数据和双峰岩浆作用（玄武岩，SiO2含量为50%，玄武岩，SiO2含量为60%）提出的。
A 3‐component broadband seismometer (STS‐2) has been deployed on the SW slope of Ambrym, Vanuatu, a large‐caldera volcano with two persistent lava lakes from July to November 2000. Well‐polarized Very Long Period Tremors (18–22s; VLPTs) occurred quite continuously, whereas other seismic signal with periods of 9s, 6–7s, 5s, 2.3–2.7s, 1.95s and 1s were intermittent. VLPTs signals show two clearly distinct directions pointing towards the caldera. Polarization orientations suggest two sources: the first one, and the most active, fits with the zone from which silicic lava flows erupted in 1986, in the central‐to‐eastern part of the caldera. The second one corresponds to the active zone formed by the complex Marum volcanic center and the Benbow cone, in the western part of the depression structure. The depths are estimated between 2.7–2.9 km with respect to sea level. VLPTs are interpreted as the quasi static‐displacement field of two nondestructive sources. They indicate the persistent continuing magmatic activity beneath the eastern floor of the caldera, although no volcanic activity is observed in this area, and the more obvious, but less active, corresponding to the lava lakes. These data also corroborate the complex internal structure of the Ambrym caldera, suggested by geological data and bimodal magmatism (basaltic, ∼50% SiO2, and silicic, ∼60% SiO2).