Kathrin Behnen, Marian Hertrich, Hansruedi Maurer, Alexis Shakas, Kai Bröker, Claire Epiney, María Blanch Jover, Domenico Giardini
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引用次数: 0
摘要
摘要应力诱发地震各向异性的假说在瑞士阿尔卑斯山的地下深层岩石实验室 Bedretto Lab 得到了验证。为了分析未受扰动的主岩中地震波速度的方向依赖性,进行了几次全面的横孔地震勘测。这就要求精确了解震源和接收器的位置,以及良好的数据质量,以便确定不同波型的行进时间。可以建立一个倾斜横向各向同性(TTI)模型,对测量数据进行一阶解释。利用 P 波和 S 波的到达时间,可以很好地约束所有相关的模型参数。然而,系统性的不拟合分布表明,可能需要一个更复杂的各向异性模型才能完全解释测量结果。这与我们的假设是一致的,即地震各向异性有很大的应力诱导成分。为了验证我们的实地测量结果,我们在实验室进行了厘米到分米尺度的更多受控实验。这些测量结果表明,岩体中的 P 波和 S 波各向异性具有可比性。对火成岩各向异性驱动机制的了解可能有助于加强对地热作业期间应力场变化的监测,从而改进危险评估规程。
Investigation of Seismic Anisotropy in the Undisturbed Rotondo Granite
Abstract. The hypothesis of stress-induced seismic anisotropy was tested in the Bedretto Lab, a deep underground rock laboratory in the Swiss alps. Several comprehensive crosshole seismic surveys were acquired to analyze the directional dependency of seismic wave velocities in the undisturbed host rock. This required precise knowledge on the source and receiver positions as well as a good data quality that allow the determination of traveltimes for different wave types. A tilted transverse isotropic (TTI) model could be established that explains the measured data to a first order. All relevant model parameters could be well constrained using P- and S-wave arrival times. However, a systematic misfit distribution indicates that a more complex anisotropy model might be required to fully explain the measurements. This is consistent with our hypothesis that seismic anisotropy has a significant stress-induced component. More controlled laboratory experiments on the centimeter to decimeter scale were performed to validate our field measurements. These measurements show a comparable order of P- and S-wave anisotropy in the rock volume. The knowledge on the driving mechanism for anisotropy in igneous rocks can potentially help to enhance the monitoring of stress field variations during geothermal operations, thereby improving hazard assessment protocols.
期刊介绍:
Solid Earth (SE) is a not-for-profit journal that publishes multidisciplinary research on the composition, structure, dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. The journal invites contributions encompassing observational, experimental, and theoretical investigations in the form of short communications, research articles, method articles, review articles, and discussion and commentaries on all aspects of the solid Earth (for details see manuscript types). Being interdisciplinary in scope, SE covers the following disciplines:
geochemistry, mineralogy, petrology, volcanology;
geodesy and gravity;
geodynamics: numerical and analogue modeling of geoprocesses;
geoelectrics and electromagnetics;
geomagnetism;
geomorphology, morphotectonics, and paleoseismology;
rock physics;
seismics and seismology;
critical zone science (Earth''s permeable near-surface layer);
stratigraphy, sedimentology, and palaeontology;
rock deformation, structural geology, and tectonics.