地殻歪と地殻内流体(<特集>火山活動と地殻応力場)
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概要
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In reviewing the relationship between groundwater and crustal strain changes, confined groundwater response to the crustal strain has been considered important, while unconfined groundwater response negligible. These studies have been mainly based on the observations of groundwater or well-water level, which directly relates to pore pressure. Most of them have adopted an isotropic and homogeneous water-saturated porous elastic medium as an aquifer model. The groundwater level response to the earth tides and atmospheric loading, which has been well investigated, has a frequency dependence governed by the form and physical constants of the aquifer and well system. This response is applicable to the analysis of the groundwater-level changes induced by fault creeps, but not always useful to comprehend those induced by earthquake occurrences, probably due to the dominant frequencies of crustal strain changes induced by the earthquakes being much larger than those by the earth tides, atmospheric loading and fault creeps. This shows the limit of the homogeneous and isotropic aquifer model. Furthermore, unconfined groundwater level changes associated with earthquake occurrences, which have been often reported, cannot be explained by the above theory. In order to understand groundwater changes induced by seismicity and volcanic activity, a new theory, which considers crustal heterogeneity, anisotropy and the interaction between confined and unconfined groundwaters, is needed.
- 特定非営利活動法人日本火山学会の論文
- 1994-09-20