Chronology and products of the 2000 eruption of Miyakejima Volcano, Japan
Chronology and products of the 2000 eruption of Miyakejima Volcano, Japan
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DOI：
10.1007/s00445-004-0404-4
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发表时间：
2005-02
影响因子：
3.5
通讯作者：
S. Nakada;M. Nagai;T. Kaneko;A. Nozawa;K. Suzuki-kamata
中科院分区：
文献类型：
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作者：
S. Nakada;M. Nagai;T. Kaneko;A. Nozawa;K. Suzuki-kamata
岩浆从日本三宅岛火山岛的横向迁移，产生了与2000年夏天的山顶爆炸有关的山顶沉降。2000年6月26日晚，三宅岛下方发生了一次地震群，次日早上，一次海底火山爆发。从三宅岛海岸到岛屿西北几十公里的海底，强烈的地震活动仍在继续。7月8日，山顶的沉降开始了山顶的喷发活动，7月和8月，爆发和沉降都间歇性地持续。最强烈的喷发事件发生在8月18日，类型为火山至次布里尼安。飞到平流层的火山灰覆盖了整个岛屿，大量的火山弹在这个时候爆发。8月29日又发生了一次大爆炸。这产生了低温火山碎屑潮，覆盖了该岛北方海岸的一个居民区。火山喷发的总体积为9.3× 106 m3（DRE），远小于由此形成的破火山口的体积（6× 108 m3）。2000年7月至8月期间，岩浆从三宅岛迁移与三宅岛西北部的地壳伸展和三宅岛本身的收缩有关。这种岩浆迁移可能导致顶板岩石进入岩浆库，产生充满热液流体和/或岩浆泡沫的地下洞穴，并在山顶形成破火山口（Oyama Caldera）。热液流体与上升岩浆的相互作用驱动了一系列的潜水岩浆喷发。可能是在岩浆运移的减弱阶段，新的岩浆从底部供给到储层，导致8月18日的爆发性排放。8月18日的事件和8月29日的潜水爆炸产生了一个管道系统，在主要喷发事件结束后，该系统允许大量的SO2排放（高达460 kg s-1）。在编写本报告时，岛上居民（约3，000人）已从三宅岛撤离3年多。
Lateral migration of magma away from Miyakejima volcanic island, Japan, generated summit subsidence, associated with summit explosions in the summer of 2000. An earthquake swarm beneath Miyakejima began on the evening of 26 June 2000, followed by a submarine eruption the next morning. Strong seismic activity continued under the sea from beneath the coast of Miyakejima to a few tens of kilometers northwest of the island. Summit eruptive event began with subsidence of the summit on 8 July and both explosions and subsidence continued intermittently through July and August. The most intense eruptive event occurred on 18 August and was vulcanian to subplinian in type. Ash lofted into the stratosphere fell over the entire island, and abundant volcanic bombs were erupted at this time. Another large explosion took place on 29 August. This generated a low-temperature pyroclastic surge, which covered a residential area on the northern coast of the island. The total volume of tephra erupted was 9.3×106m3(DRE), much smaller than the volume of the resulting caldera (6×108m3). Migration of magma away from Miyakejima was associated with crustal extension northwest of Miyakejima and coincident shrinkage of Miyakejima Island itself during July–August 2000. This magma migration probably caused stoping of roof rock into the magma reservoir, generating subsurface cavities filled with hydrothermal fluid and/or magmatic foam and formation of a caldera (Oyama Caldera) at the summit. Interaction of hydrothermal fluid with ascending magma drove a series of phreatic to phreatomagmatic eruptions. It is likely that new magma was supplied to the reservoir from the bottom during waning stage of magma’s migration, resulting in explosive discharge on 18 August. The 18 August event and phreatic explosions on 29 August produced a conduit system that allowed abundant SO2emission (as high as 460 kg s−1) after the major eruptive events were over. At the time of writing, inhabitants of the island (about 3,000) have been evacuated from Miyakejima for more than 3 years.