Abstract

Extensometer data have an advantage over satellite-based data for monitoring land subsidence in that extensometer data provide continuous measurements (hourly or better temporal resolution) at very high precision (several tens of microns) over a known depth interval; the latter is important for isolating groundwater pumping from other causes of land subsidence attributed to tectonics or eustatic adjustments in the Earth’s crust. This investigation aims to identify a semi-analytical procedure for quantifying aquifer and aquitard properties from a single extensometer record in lieu of the time-consuming development of more complex numerical models to quantify and constrain these parameter values. In spite of a limited 12-year record and the fact that water levels both decline and increase on an annual basis, this study successfully and reasonably estimated both aquifer and aquitard parameters at the Lorenzi extensometer site in Las Vegas Valley, Nevada (USA), when compared to the estimates developed numerically. The key factors that allow for estimates of elastic and inelastic skeletal-specific storage and hydraulic conductivity of the aquitards and elastic specific storage and hydraulic conductivity of the intervening aquifers is the presence of pumping cycles at multiple frequencies, and measured heads at all the aquifer units covered in the extensometer record. There is an inherent assumption that the aquitards possess the same hydrologic characteristics and are homogeneous and isotropic. This assumption is also a usual limitation in numerical modeling of these settings because of the complex temporal head relationships occurring within the aquitards that are rarely, if ever, measured.

中文翻译：

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引伸计取证：数据能真正告诉我们什么？

摘要

引伸计数据在监测地面沉降方面优于基于卫星的数据，因为引伸计数据可以在已知的深度间隔内以非常高的精度（数十微米）进行连续测量（每小时或更长时间的分辨率）。后者对于将地下水泵与地面沉降的其他原因隔离开来很重要，而地面沉降是由于地壳的构造或向东调整所致。这项研究旨在确定一种半分析程序，用于从单个引伸计记录中量化含水层和阿奎尔塔特性，而不是耗时地开发更复杂的数值模型以量化和约束这些参数值。尽管12年的记录有限，而且水位每年都在下降和上升，与数值计算得出的估算值相比，这项研究成功，合理地估算了内华达州拉斯维加斯谷地洛伦兹引伸计现场的含水层和阿奎塔参数。估算含水层的弹性和非弹性骨架比储量和水力传导率以及中间含水层的弹性比储量和水力传导率的关键因素是存在多个频率的抽运周期，并且在所有含水层单元都测得水头在引伸计记录中。有一个固有的假设，即阿奎德具有相同的水文特征，并且是均质的和各向同性的。