期刊
GEOPHYSICAL JOURNAL INTERNATIONAL
卷 180, 期 2, 页码 685-696出版社
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-246X.2009.04445.x
关键词
Controlled source seismology; Seismic tomography; Volcano seismology; Volcanic arc processes; Crustal structure; Volcano monitoring
资金
- National Science Foundation
- National Environmental Research Council
- British Geological Survey (BGS)
- Incorporated Research Institutions for Seismology (IRIS)
- Discovery Channel TV
- British Foreign & Commonwealth Office (FCO)
- NERC [bgs05003] Funding Source: UKRI
- Natural Environment Research Council [bgs05003] Funding Source: researchfish
To better understand the volcanic phenomena acting on Montserrat, the SEA-CALIPSO seismic experiment (Seismic Experiment with Airgun-source - Caribbean Andesitic Lava Island Precision Seismo-geodetic Observatory) was conducted in 2007 December with the aim of imaging the upper crust and the magmatic system feeding the active Soufriere Hills Volcano. The 3-D survey covered an area of about 50 x 40 km and involved the deployment of 247 land stations and ocean-bottom seismometers (OBSs). A subset of the data, recorded by four OBSs and four land stations on a southeast to northwest line, has been analysed, and traveltimes have been inverted to obtain a 2-D seismic velocity model through the island. Inverted phases include crustal and sediment P waves and wide-angle reflections. The resulting velocity model reveals the presence of a high velocity body (3.5-5.5 km s(-1)) beneath the island, with highest velocities beneath the Soufriere and Centre Hills, corresponding primarily to the cores of these volcanic edifices, built of a pile of andesite lava domes and subsequent intrusions. In the offshore region, velocities in the surficial sediment layer vary from 1.5 to 3.0 km s(-1), consistent with a mainly calcareous and volcaniclastic composition. A wide-angle reflector is observed at a depth of similar to 1200 m below the seabed, and appears to deepen beneath the island. The upper crust beneath this reflector has velocities of 4.0-6.0 km s(-1) and is inferred to correspond to plutonic and hypabyssal rocks and sedimentary material of the old arc. The high velocity region beneath the island, extends into the crust to a depth of at least 5 km, and is believed to be caused by an intrusive complex, possibly of intermediate composition. A low velocity zone, as would be expected in the presence of an active magma chamber, was not observed perhaps due to the limited resolution beneath similar to 5 km depth. Our results so far provide the first wide-angle seismic constraints on the upper crustal structure of the island to a depth of 10 km, and will help understanding the processes that drive volcanism at Montserrat and other island arc volcanoes.
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