Numerical simulations of flood basalt lava flows: Roles of parameters on lava flow morphologies
Numerical simulations of flood basalt lava flows: Roles of parameters on lava flow morphologies
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溢流玄武岩熔岩流的数值模拟：参数对熔岩流形态的作用
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
S. Sasaki
中科院分区：
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作者：
H. Miyamoto;S. Sasaki
利用三维熔岩流数值模拟模型，研究了参数对简单溢流玄武岩熔岩流形态的影响。该模型可以提供一个更真实的描述熔岩流的形态比二维模型，因为它可以评估喷发的体积和熔岩长度之间的复杂关系，通过考虑流动的横向蔓延。此外，我们的模型可以计算熔岩形态上一个非常温和的斜坡，甚至在一个平面上没有网格方向的依赖。它不仅可以模拟单个火山上的小规模流动，而且可以模拟大规模（>100公里）流动，而不会出现数值不稳定。虽然熔岩流的长度由许多参数控制，包括流变特性和喷发速率，但长度不是这些参数的简单函数。我们确认，如倾角和粘度的参数的微小变化可以影响流的长度。将喷发速率增加到107 m3/s，使玄武岩熔岩流更长。然而，在高于107 m3/s的喷发速率在0.3°斜坡，流动长度不会增加超过107 m3/s的喷发速率，由于喷发熔岩的体积守恒。因此，喷发条件不能仅从熔岩流的长度来估计。因此，由以前的二维模型获得的估计喷发率，基本上是从流的长度估计喷发率，并不总是揭示有用的值。另一方面，一个简单的熔岩流的宽度是一个很好的衡量其喷发速率，因为宽度主要是由喷发速率和屈服强度控制。一个简单的熔岩，其宽度大于100公里，几乎可以肯定是在高于107立方米/秒的喷发率侵位，如果流的屈服强度是在玄武岩的范围。
Using a three-dimensional numerical simulation model of lava flow, we studied the effects of parameters on the morphologies of simple flood basalt lava flows. The model can provide a more realistic description of morphologies of lava flows than two-dimensional models because it can evaluate the complex relationship between erupted volume and length of lava by considering lateral spreading of flows. Moreover, our model can calculate lava morphologies on a very moderate slope or even on a flat plane without mesh direction dependency. It can simulate not only small-scale flows on individual volcanoes but also large-scale (>100 km) flows without numerical instability. Although the length of a lava flow is controlled by many parameters including rheological properties and eruption rate, the length is not a simple function of these parameters. We confirm that small changes in parameters such as slope angle and viscosity can affect the length of the flow. Increasing the eruption rate up to 107 m3/s makes basaltic lava flows longer. However, at eruption rates higher than 107 m3/s on 0.3° slopes, flow length does not increase beyond that of the 107 m3/s eruption rate due to volume conservation of erupted lava. Thus eruption conditions cannot be estimated from the length of a lava flow alone. Therefore the estimated eruption rate obtained by previous two-dimensional models, which essentially estimate eruption rate from the length of the flow, will not always reveal useful values. On the other hand, the width of a simple lava flow is a good measure of its eruption rate because the width is mainly controlled by the eruption rate and yield strength. A simple lava whose width is greater than 100 km was almost certainly emplaced at eruption rates higher than 107 m3/s if the yield strength of the flow is in a basaltic range.