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Earthquake-induced hydrogeological changes in New Zealand

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posted on 2023-09-22, 01:43 authored by Weaver, Konrad Cedd

Earthquakes redistribute fluids and change associated flow paths in the subsurface. Earthquake hydrology is an evolving discipline that studies such phenomena, providing novel information on crustal processes, natural hazards and water resources. This thesis uses the internationally significant New Zealand "hydroseismicity" dataset, in a regional-scale multi-site multi-earthquake study which includes the occurrence and the absence of responses, spanning a decade. Earthquake-induced groundwater level and tidal behaviour changes were examined in a range of aquifers, rock types and hydrogeological settings. Monitoring wells were within one (near-field) to several (intermediate- field) ruptured fault lengths of a variety of earthquakes that had a range of shaking intensities. This thesis presents three studies on the seismic and hydrogeological controls on earthquake-induced groundwater level changes.  Water level changes were recorded New Zealand-wide within compositionally diverse, young shallow aquifers, in 433 monitoring wells at distances between 4 and 850 km from the 2016 Mw 7.8 Kaikoura earthquake epicentre. Water level changes are inconsistent with static stress changes, but do correlate with peak ground acceleration (PGA). At PGAs exceeding ~2 m/s2, water level changes predominantly increased persistently, which may have resulted from shear-induced consolidation. At lower PGAs there were approximately equal numbers of persistent water level increases and decreases, which are thought to have resulted from permeability enhancement. Water level changes also occurred more frequently north of the epicentre, due to the northward directivity of the Kaikoura earthquake rupture. Local hydrogeological conditions also contributed to the observed responses, with larger water level changes occurring in deeper wells and in well-consolidated rocks at equivalent PGA levels.  Earthquakes have previously been inferred to induce hydrological changes in aquifers on the basis of changes to well tidal behaviour and water level, but the relationship between these changes have been unclear. Earthquake-induced changes to tidal behaviour and groundwater levels were quantified in 161 monitoring wells screened in gravel aquifers in Canterbury, New Zealand. In the near-field of the Canterbury earthquake sequence of 2010 and 2011, permeability reduction detected by tidal behaviour changes and increased water levels supports the hypothesis of shear-induced consolidation. Water level changes that occurred with no change in tidal behaviour re-equilibrated at a new post-seismic level within ~50 minutes possibly due to high permeability, good well-aquifer coupling, and/or small permeability changes in the local aquifer. Water level changes that occurred with tidal behaviour changes took from ~240 minutes to ~10 days to re-equilibrate, thought to represent permeability changes on a larger scale. Recent studies commonly utilise a general metric for earthquake-induced hydrological responses based on epicentral distance, earthquake magnitude and seismic energy density. A logistic regression model with random effects was applied to a dataset of binary responses of 495 monitoring well water levels to 11 Mw 5.4 or larger earthquakes. Within the model, earthquake shaking (represented by peak ground velocity), degree of confinement (depth) and rock strength (site average shear wave velocity in the shallow subsurface) were incorporated. For practical applications, the probabilistic framework was converted into the Modified Mercalli (MM) intensity scale. The model shows that water level changes are unlikely below MM intensity VI. At an MM intensity VII, water level changes are about as likely as not to very likely. At MM intensity VIII, the likelihood rises to very likely to virtually certain. This study was the first attempt we are aware of worldwide at incorporating both seismic and hydrogeological factors into a probabilistic framework for earthquake-induced groundwater level changes. The framework is a novel and more universal approach in quantifying responses than previous metrics using epicentral distance, magnitude and seismic energy density. It has potential to enable better comparison of international studies and inform practitioners making decisions around investment to mitigate risk to, and to increase the resilience of, water supply infrastructure.


Copyright Date


Date of Award



Te Herenga Waka—Victoria University of Wellington

Rights License

CC BY 4.0

Degree Discipline

Earth Sciences

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level


Degree Name

Doctor of Philosophy

Victoria University of Wellington Unit

Institute of Geophysics

ANZSRC Type Of Activity code


Victoria University of Wellington Item Type

Awarded Doctoral Thesis



Victoria University of Wellington School

School of Geography, Environment and Earth Sciences


Cox, Simon; Townend, John

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    earthquake hydrologyseismologyearthquakeshydrogeologyhydrologyaquifersgroundwaterfluid flowseismicitySchool: School of Geography, Environment and Earth SciencesUnit: Institute of Geophysics040403 Geophysical Fluid Dynamics040407 Seismology and Seismic Exploration040608 Surfacewater Hydrology040604 Natural Hazards040603 Hydrogeology040607 Surface Processes040313 Tectonics961005 Natural Hazards in Fresh, Ground and Surface Water Environments961002 Natural Hazards in Coastal and Estuarine Environments961007 Natural Hazards in Mining Environments961010 Natural Hazards in Urban and Industrial Environments961008 Natural Hazards in Mountain and High Country Environments961009 Natural Hazards in Sparseland, Permanent Grassland and Arid Zone Environments961004 Natural Hazards in Forest and Woodlands Environments961003 Natural Hazards in Farmland, Arable Cropland and Permanent Cropland Environments961101 Physical and Chemical Conditions of Water for Urban and Industrial Use961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments961103 Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and Industrial Use)960903 Coastal and Estuarine Water Management960905 Farmland, Arable Cropland and Permanent Cropland Water Management960907 Forest and Woodlands Water Management960908 Mining Land and Water Management960909 Mountain and High Country Land and Water Management960910 Sparseland, Permanent Grassland and Arid Zone Land and Water Management960912 Urban and Industrial Water Management960913 Water Allocation and Quantification960703 Environmental Education and Awareness960706 Rural Water Policy960709 Urban Water Policy960608 Rural Water Evaluation (incl. Water Quality)960611 Urban Water Evaluation (incl. Water Quality)960604 Environmental Management Systems960506 Ecosystem Assessment and Management of Fresh, Ground and Surface Water EnvironmentsDegree Discipline: GeophysicsDegree Discipline: HydrogeologyDegree Discipline: GeologyDegree Discipline: Earth SciencesDegree Level: DoctoralDegree Name: Doctor of PhilosophyTectonicsGeophysical Fluid DynamicsSeismology and Seismic ExplorationHydrogeologyNatural HazardsSurface ProcessesSurfacewater Hydrology



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