Seismological evidence for Lateral magma intrusion during the July 1978 deflation of the Krafla volcano in NE-Iceland
Seismological evidence for Lateral magma intrusion during the July 1978 deflation of the Krafla volcano in NE-Iceland
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1978 年 7 月冰岛东北部克拉夫拉火山塌陷期间横向岩浆侵入的地震学证据
DOI：
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
B. Brandsdóttir
中科院分区：
文献类型：
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作者：
P. Einarsson;B. Brandsdóttir
1978 年 7 月发生在冰岛东北部火山裂谷带的克拉夫拉火山的通货紧缩在大多数方面都是自 1975 年 12 月以来在克拉夫拉发生的许多通货紧缩事件的典型。除了缓慢的通货膨胀时期之外，通货紧缩事件的特点是破火山口地区的快速沉降、火山震颤和横断火山的断层群中的广泛裂谷。紧缩开始后不久，破火山口地区的地震就会加剧，并沿着断层群远离火山中心部分传播，有时可达 65 公里。紧缩事件被解释为地下岩浆运动的结果，来自克拉夫拉储层的岩浆横向注入断层群形成岩脉。在 1978 年 7 月的事件中，岩浆被注入北部断层群总距离 30 公里。在前9小时内，堤尖以0.4-0.5 m/sec的速度扩展，但随着堤坝长度的增加，速度降低。结合地表变形数据，这些数据可用于估计岩脉的横截面积和岩浆的驱动压力。沿着堤坝的横截面积是可变的，并且在地震活动最活跃的区域中横截面积最大。平均值约为 1200 m{sup 2}。岩浆库和岩堤尖端之间的压力差约为 10-40 巴，并且在注入过程中变化不大。« less
The July 1978 deflation of the Krafla volcano in the volcanic rift zone of NE-Iceland was in most respects typical of the many deflation events that have occurred at Krafla since December 1975. Separated by periods of slow inflation, the deflation events are characterized by rapid subsidence in the caldera region, volcanic tremor and extensive rifting in the fault swarm that transects the volcano. Earthquakes increase in the caldera region shortly after deflation starts and propagate along the fault swarm away from the central part of the volcano, sometimes as far as 65 km. The deflation events are interpreted as the result of subsurface magmatic movements, when magma from the Krafla reservoir is injected laterally into the fault swarm to form a dyke. In the July 1978 event magma was injected a total distance of 30 km into the northern fault swarm. The dyke tip propagated with the velocity of 0.4-0.5 m/sec during the first 9 hours, but the velocity decreased as the length of the dyke increased. Combined with surface deformation data, these data can be used to estimate the cross sectional area of the dyke and the driving pressure of the magma. The cross sectional area is variablemore » along the dyke and is largest in the regions of maximum earthquake activity. The average value is about 1200 m{sup 2}. The pressure difference between the magma reservoir and the dyke tip was of the order of 10-40 bars and did not change much during the injection.« less