Seismically induced hydrologic responses: A comprehensive field, experimental and modeling study
by Mingyuan Wang
Date of Examination:2024-12-16
Date of issue:2025-01-07
Advisor:Prof. Dr. Martin Sauter
Referee:Prof. Dr. Martin Sauter
Referee:Prof. Dr. Hongbiao Gu
Persistent Address:
http://dx.doi.org/10.53846/goediss-10974
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Abstract
English
Seismically induced hydrologic phenomena have been observed and documented for thousands of years. The studies of these phenomena are scientifically significant, providing a new perspective in understanding the interplay between tectonic activity and hydrological processes. On the other hand, these studies also have practical implications, as hydrological responses triggered by earthquakes could be related to groundwater supply, underground pollution storage, oil and gas extraction, and potential geological risks. Consequently, the investigation into hydrologic reactions triggered by earthquakes has become a focal point within the field of earthquake hydrology, with numerous mechanisms put forth in past research. Nevertheless, the comprehension of these seismically induced hydrological responses is still limited, given the complexities associated with multiple influencing factors, the lack of real-time access to crucial parameters, and the oversimplifying tendency of postulated theories, etc. In this dissertation, utilizing field, experimental, and modeling research methods to provide a comprehensive examination and understanding of seismically induced hydrologic responses, specifically the changes in water levels and permeability in wells following earthquakes. This study proposes to address some of the existing limitations within theoretical models, bridge the gap for real-time parameters, and accurately depict the flow behaviors of well-aquifer systems and groundwater and manifested hydrologic responses under seismic disturbances. Chapter 2 deals with field observation and interpretation of seismically induced hydrologic responses. This Chapter presents an extensive field study on the spatial and temporal variation of aquifer permeability in the North China Plain. Results indicate that permeability is not a fixed parameter but is constantly self-adjusting on its background value. These variations significantly influence by the magnitude and azimuth of seismic events. Furthermore, background permeability values and their changes are not uniform across different aquifers, revealing the complexity of aquifer responses to seismic activities. Importantly, implications of these results highlight, particularly the impact on crustal geomechanics. Chapter 3 conducts experimental and quantitative verification of seismically induced hydrologic responses. Building from field findings, this chapter focuses on a laboratory-scale study to understand the impact of mechanical loading on a confined, saturated porous medium. It confirms that dynamic shaking can lead to significant and non-uniform deformation in sandy sediments, leading to the change in porosity and permeability. The irreversible nature of these changes underscores their potential significance in dictating seismic-wave-induced hydraulic responses. Chapter 4 experimentally and numerically investigate impacts of confining layer on seismically induced hydrologic responses. The methodological approach expands in this chapter, combining both experimental and numerical simulation methods. The study confirms and quantifies that earthquakes can trigger the reorganization of groundwater flow, even causing upward flow from sandy layers into overlying clay layers. Diverse hydraulic properties in the sand and clay layers significantly influence the earthquake-induced pore pressure changes and the subsequent water flow patterns. Chapter 5 numerically explore effects of wellbore and skin zone on seismically induced hydrologic responses. A numerical simulation model is built to integrate the findings from the previous research, incorporating the role of the wellbore and the skin zone. It establishes that the geometry of wellbore and skin zone characteristics significantly influence co-seismic water-level oscillations, especially under high-frequency perturbations. However, these can be reasonably overlooked when examining co-seismic water level step changes due to their comparatively smaller influence. The field, experimental and numerical simulation results in this study prove to be mutually supportive with robust and innovative results. These findings hold substantial implications for improving the prediction and assessment of seismically induced hydrologic responses, mitigating earthquake's impact on water resources and potential geologic hazards through a more quantitative approach.
Keywords: Groundwater level; Earthquake; Hydrological response; Permeability
