A dynamic balance between magma supply and eruption rate at Kilauea volcano, Hawaii
A dynamic balance between magma supply and eruption rate at Kilauea volcano, Hawaii
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夏威夷基拉韦厄火山岩浆供应和喷发率之间的动态平衡
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发表时间：
1997
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通讯作者：
R. Denlinger
中科院分区：
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作者：
R. Denlinger
利用基拉韦厄火山岩浆供给与喷口喷出量的动态平衡，估算了基拉韦厄火山岩浆储存量和岩浆供给速率。在1991年的大部分时间里，基拉韦厄东部裂谷区的库帕亚纳哈喷口的体积通量呈线性下降，这与基拉韦厄山顶高度的抛物线变化有关，因为喷口的流量最初超过了火山的岩浆供应，然后落后于岩浆供应。根据30多年的数据建立的峰顶高度和倾斜之间的对应关系提供了峰顶高度的每日倾斜估计。峰顶倾斜度和高程呈抛物线变化的最小值（或高程变化为零）出现在火山下方向库区的岩浆供给量与库区向地表的岩浆供给量相等时，因此当天的岩浆供给量由喷口通量给出。1991年6月19日，基拉韦厄火山的岩浆供给量为21.7万±1万m3/d（0.079±0.004 km3/yr）。这接近于1958年至1984年间0.08 km3/年的平均喷发速率。此外，1983年以来普乌东裂谷带每次喷发对峰顶高度和倾斜的可预测响应表明，峰顶变形也是岩浆库压力的一个指标。因此，Puu Oo熔岩湖（库帕亚纳哈隆起4 km，距峰顶18 km）的海拔高度与峰顶倾斜度的相关性可以估计峰顶倾斜度变化所对应的岩浆压力变化。喷口活动期间的体积变化与储层压力变化之比（dV/dP）可以用喷发体积与峰顶倾斜度变化之比（dV/dtilt）除以压力变化与峰顶倾斜度变化之比（dP/dtilt）来确定。这一dV/dP测量值，结合拉斑岩熔体体积模量的实验室测量值，提供了基拉韦厄岩浆储层的体积估计为240±50 km3。这个估计比传统的估计要大得多，但与基拉韦厄岩浆系统的地震层析成像和地球物理模拟一致。
The dynamic balance between magma supply and vent output at Kilauea volcano is used to estimate both the volume of magma stored within Kilauea volcano and its magma supply rate. Throughout most of 1991 a linear decline in volume flux from the Kupaianaha vent on Kilauea's east rift zone was associated with a parabolic variation in the elevation of Kilauea's summit as vent output initially exceeded then lagged behind the magma supply to the volcano. The correspondence between summit elevation and tilt established with over 30 years of data provided daily estimates of summit elevation in terms of summit tilt. The minimum in the parabolic variation in summit tilt and elevation (or zero elevation change) occurs when the magma supply to the reservoir from below the volcano equals the magma output from the reservoir to the surface, so that the magma supply rate is given by vent flux on that day. The measurements of vent flux and tilt establish that the magma supply rate to Kilauea volcano on June 19, 1991, was 217,000±10,000 m3/d (or 0.079±0.004 km3/yr). This is close to the average eruptive rate of 0.08 km3/yr between 1958 and 1984. In addition, the predictable response of summit elevation and tilt to each east rift zone eruption near Puu Oo since 1983 shows that summit deformation is also a measure of magma reservoir pressure. Given this, the correlation between the elevation of the Puu Oo lava lake (4 km uprift of Kupaianaha and 18 km from the summit) and summit tilt provides an estimate for magma pressure changes corresponding to summit tilt changes. The ratio of the change in volume to the change in reservoir pressure (dV/dP) during vent activity may be determined by dividing the ratio of volume erupted to change in summit tilt (dV/dtilt) by the ratio of pressure change to change in summit tilt (dP/dtilt). This measure of dV/dP, when combined with laboratory measurements of the bulk modulus of tholeitic melt, provides an estimate of 240±50 km3 for the volume of Kilauea's magma reservoir. This estimate is much larger than traditional estimates but consistent with seismic tomographic imaging and geophysical modeling of Kilauea's magma system.