scholarly journals Earthquake-induced hydrologic changes in the geoengineered schist landslides of Cromwell Gorge, Central Otago

2021 ◽  
Author(s):  
◽  
Grant O'Brien
Keyword(s):  
Groundwater Level ◽  
Recovery Time ◽  
Hydraulic Properties ◽  
Peak Pressure ◽  
Pressure Change ◽  
Monitoring Site ◽  
Flow Rates ◽  
Time To Peak ◽  
Hydrological Responses ◽  
Groundwater Level Changes

<p>Geoengineered groundwater systems located within seven large (> 100 ha surface area), deep-seated, slow-creep schist landslides in Cromwell Gorge (Otago, New Zealand) are observed to respond systematically to 10 large (>Mw6.2), regional earthquakes at epicentral distances of 130-630 km. The permeabilities of the schist landslides have previously been reported to be c. 1 x 10⁻¹⁷ - 4 x 10⁻⁶ m2 and the permeability structure is dominated by large fracture zones. Of the 315 hydrological instruments in the gorge for which data have been analysed, 21 monitoring well piezometers record repeated metre- or centimetre-scale groundwater level changes, and 12 underground V-notch weirs record elevated flow rates induced by the same earthquakes. Groundwater level changes exhibit consistent temporal characteristics at all monitoring sites, namely a time to peak pressure change on the order of one month and a subsequent recovery period on the order of one year. Changes in weir flow rate are near-instantaneous with maximum flow rates reached within 0-6 hours, followed by recession periods on the order of one month. Hydrological responses to different earthquakes at each monitoring site are systematic in terms of polarity and amplitude. This comprehensive dataset enables consistent patterns in the amplitude, time to peak pressure change and recovery time of groundwater level changes, and elevated weir discharge volumes in response to earthquake shaking to be documented. Earthquakes inducing hydrological responses have been categorised into five categories based on shaking characteristics (duration, bandwidth and amplitude). Larger hydrological responses and proportionally shorter time to peak pressure change and recovery time are associated with long duration (25-50 s or longer), high-amplitude, broad bandwidth shaking. The larger amplitudes of hydrological response and proportionally shorter times to peak pressure change and recovery times, are interpreted to represent greater temporary enhancement of the landslides hydraulic properties, particularly permeability. Understanding how earthquakes can enhance or otherwise affect hydraulic properties such as permeability in fractured reservoirs is intrinsically important and may prove of economic utility for both the geothermal and hydrocarbon energy sectors.</p>

scholarly journals Earthquake-induced hydrologic changes in the geoengineered schist landslides of Cromwell Gorge, Central Otago

2021 ◽  
Author(s):  
◽  
Grant O'Brien
Keyword(s):  
Groundwater Level ◽  
Recovery Time ◽  
Hydraulic Properties ◽  
Peak Pressure ◽  
Pressure Change ◽  
Monitoring Site ◽  
Flow Rates ◽  
Time To Peak ◽  
Hydrological Responses ◽  
Groundwater Level Changes

<p>Geoengineered groundwater systems located within seven large (> 100 ha surface area), deep-seated, slow-creep schist landslides in Cromwell Gorge (Otago, New Zealand) are observed to respond systematically to 10 large (>Mw6.2), regional earthquakes at epicentral distances of 130-630 km. The permeabilities of the schist landslides have previously been reported to be c. 1 x 10⁻¹⁷ - 4 x 10⁻⁶ m2 and the permeability structure is dominated by large fracture zones. Of the 315 hydrological instruments in the gorge for which data have been analysed, 21 monitoring well piezometers record repeated metre- or centimetre-scale groundwater level changes, and 12 underground V-notch weirs record elevated flow rates induced by the same earthquakes. Groundwater level changes exhibit consistent temporal characteristics at all monitoring sites, namely a time to peak pressure change on the order of one month and a subsequent recovery period on the order of one year. Changes in weir flow rate are near-instantaneous with maximum flow rates reached within 0-6 hours, followed by recession periods on the order of one month. Hydrological responses to different earthquakes at each monitoring site are systematic in terms of polarity and amplitude. This comprehensive dataset enables consistent patterns in the amplitude, time to peak pressure change and recovery time of groundwater level changes, and elevated weir discharge volumes in response to earthquake shaking to be documented. Earthquakes inducing hydrological responses have been categorised into five categories based on shaking characteristics (duration, bandwidth and amplitude). Larger hydrological responses and proportionally shorter time to peak pressure change and recovery time are associated with long duration (25-50 s or longer), high-amplitude, broad bandwidth shaking. The larger amplitudes of hydrological response and proportionally shorter times to peak pressure change and recovery times, are interpreted to represent greater temporary enhancement of the landslides hydraulic properties, particularly permeability. Understanding how earthquakes can enhance or otherwise affect hydraulic properties such as permeability in fractured reservoirs is intrinsically important and may prove of economic utility for both the geothermal and hydrocarbon energy sectors.</p>

scholarly journals Spatially and temporally systematic hydrologic changes within large geoengineered landslides, Cromwell Gorge, New Zealand, induced by multiple regional earthquakes

2021 ◽  
Author(s):  
GA O'Brien ◽  
SC Cox ◽  
John Townend
Keyword(s):  
Groundwater Level ◽  
Spectral Characteristics ◽  
Seismic Energy ◽  
High Amplitude ◽  
Ground Acceleration ◽  
Earthquake Parameters ◽  
Groundwater Levels ◽  
Time To Peak ◽  
Long Duration ◽  
Groundwater Level Changes

©2016. American Geophysical Union. All Rights Reserved. Geoengineered groundwater systems within seven large (23 × 104–9 × 106 m2), deep-seated (40–300 m), previously slow-creep (2–5 mm/yr.) schist landslides in the Cromwell Gorge responded systematically to 11 large (Mw > 6.2) earthquakes at epicentral distances of 130–630 km between 1990 and 2013. Landslide groundwater is strongly compartmentalized and often overpressured, with permeability of 10−17 to 10−13 m2 and flow occurring primarily through fracture and crush zones, hindered by shears containing clayey gouge. Hydrological monitoring recorded earthquake-induced meter- or centimeter-scale changes in groundwater levels (at 22 piezometers) and elevated drainage discharge (at 11 V notch weirs). Groundwater level changes exhibited consistent characteristics at all monitoring sites, with time to peak-pressure changes taking ~1 month and recovery lasting 0.7–1.2 years. Changes in weir flow rate near instantaneous (peaking 0–6 h after earthquakes) and followed by recession lasting ~1 month. Responses at each site were systematic from one earthquake to another in terms of duration, polarity, and amplitude. Consistent patterns in amplitude and duration have been compared between sites and with earthquake parameters (peak ground acceleration (PGA), seismic energy density (e), shaking duration, frequency bandwidth, and site amplitude). Shaking at PGA ~0.27% g and e ~ 0.21 J m−3 induced discernable gorge-wide hydrological responses at thresholds comparable to other international examples. Groundwater level changes modeled using a damped harmonic oscillator characterize the ability of the system to resist and recover from extrinsic perturbations. The observed character of response reflects spectral characteristics as well as energy. Landslide hydrological systems appear most susceptible to damage and hydraulic changes when earthquakes emit broad-frequency, long-duration, high-amplitude ground motion.

Different responses of groundwater level changes through hydrogeological characteristics due to M5.4 Pohang earthquake

2020 ◽  
Author(s):  
Soo-Hyoung Lee ◽  
Jae Min Lee ◽  
Heesung Yoon ◽  
Yongje Kim
Keyword(s):  
Groundwater Level ◽  
Hydraulic Properties ◽  
Seismic Waves ◽  
Observation Well ◽  
Monitoring Wells ◽  
Level Change ◽  
Hydrogeological Characteristics ◽  
Pass Through ◽  
Groundwater Level Change ◽  
Groundwater Level Changes

&lt;p&gt;Earthquake of magnitude M5.4 the second largest recorded earthquake occurred in Pohang, South Korea at 05:29:32 (UTC time) on November 15, 2017. The M5.4 event and hundreds of aftershocks produced extreme impacts across the area to date along with human and property damages. The distance between the epicenter of the M5.4 Pohang earthquake and the groundwater observation well is about 43 km for KJ-well and about 76 km for YS-well. Records from these two monitoring wells showed groundwater level changes occurred in 2017-11-15 05:30 (UTC time), about 30 seconds after the earthquake. In KJ-well, 8.0 cm of groundwater level change was observed, and in YS-well, about 30.0 cm of groundwater level change. The changes in groundwater level appeared to be a spike-like pattern that rises immediately due to the compressive action of the aquifer as the seismic waves pass through and then return to its original state. Interestingly, the groundwater level changes in YS-well was observed to be approximately three times greater than KJ-well although YS-well is approximately twice as far from the epicenter as KJ-well. The factors causing these different changes were compared and analyzed for the geometry, hydraulic properties, and geological characteristics of the well locations&lt;/p&gt;

scholarly journals Spatially and temporally systematic hydrologic changes within large geoengineered landslides, Cromwell Gorge, New Zealand, induced by multiple regional earthquakes

2021 ◽  
Author(s):  
GA O'Brien ◽  
SC Cox ◽  
John Townend
Keyword(s):  
Groundwater Level ◽  
Spectral Characteristics ◽  
Seismic Energy ◽  
High Amplitude ◽  
Ground Acceleration ◽  
Earthquake Parameters ◽  
Groundwater Levels ◽  
Time To Peak ◽  
Long Duration ◽  
Groundwater Level Changes

©2016. American Geophysical Union. All Rights Reserved. Geoengineered groundwater systems within seven large (23 × 104–9 × 106 m2), deep-seated (40–300 m), previously slow-creep (2–5 mm/yr.) schist landslides in the Cromwell Gorge responded systematically to 11 large (Mw > 6.2) earthquakes at epicentral distances of 130–630 km between 1990 and 2013. Landslide groundwater is strongly compartmentalized and often overpressured, with permeability of 10−17 to 10−13 m2 and flow occurring primarily through fracture and crush zones, hindered by shears containing clayey gouge. Hydrological monitoring recorded earthquake-induced meter- or centimeter-scale changes in groundwater levels (at 22 piezometers) and elevated drainage discharge (at 11 V notch weirs). Groundwater level changes exhibited consistent characteristics at all monitoring sites, with time to peak-pressure changes taking ~1 month and recovery lasting 0.7–1.2 years. Changes in weir flow rate near instantaneous (peaking 0–6 h after earthquakes) and followed by recession lasting ~1 month. Responses at each site were systematic from one earthquake to another in terms of duration, polarity, and amplitude. Consistent patterns in amplitude and duration have been compared between sites and with earthquake parameters (peak ground acceleration (PGA), seismic energy density (e), shaking duration, frequency bandwidth, and site amplitude). Shaking at PGA ~0.27% g and e ~ 0.21 J m−3 induced discernable gorge-wide hydrological responses at thresholds comparable to other international examples. Groundwater level changes modeled using a damped harmonic oscillator characterize the ability of the system to resist and recover from extrinsic perturbations. The observed character of response reflects spectral characteristics as well as energy. Landslide hydrological systems appear most susceptible to damage and hydraulic changes when earthquakes emit broad-frequency, long-duration, high-amplitude ground motion.

scholarly journals Groundwater-level changes in response to bursts of seismic activity off the Izu Peninsula, Japan

1999 ◽  
Vol 26 (16) ◽  
pp. 2501-2504 ◽  
Author(s):  
Masao Ohno ◽  
Tsutomu Sato ◽  
Kenji Notsu ◽  
Hiroshi Wakita ◽  
Kunio Ozawa
Keyword(s):  
Groundwater Level ◽  
Seismic Activity ◽  
Izu Peninsula ◽  
Groundwater Level Changes

scholarly journals Hydraulic Tomography for Estimating the Diffusivity of Heterogeneous Aquifers Based on Groundwater Response to Tidal Fluctuation in an Artificial Island in Taiwan

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Jet-Chau Wen ◽  
Hong-Ru Lin ◽  
Tian-Chyi Jim Yeh ◽  
Yu-Li Wang ◽  
Keng-Li Lin ◽  
...  
Keyword(s):  
Groundwater Level ◽  
Hydraulic Properties ◽  
Tidal Fluctuation ◽  
Heterogeneous Aquifers ◽  
Hydraulic Diffusivity ◽  
The Real ◽  
Groundwater Levels ◽  
Hydraulic Tomography ◽  
Groundwater Response ◽  
Spectrum Ratio

This study investigated the hydraulic properties of the heterogeneous aquifers of an artificial island (Yunlin Offshore Industrial Park) in Taiwan. The research was based on the groundwater level response affected by tidal fluctuation using the hydraulic tomography (HT) to analyze the hydraulic diffusivity (α). Specifically, the power spectrum ratio of groundwater and tidal fluctuations derived from the Gelhar solution was used to estimate α in homogeneous aquifers; this, however, could not be applied in the artificial island. Next, the spatial distribution of the groundwater level response affected by tidal fluctuation was analyzed and found to be irregular, proving the existence of hydrogeological heterogeneity in the artificial island. Furthermore, the results of the estimated α using the HT showed low error and high correlation, 0.41 m2/hr and 0.83, respectively, between the optimal estimated heterogeneous and reference α fields in the synthetic aquifer. Last, the HT was used in the real tested scenario. By comparing the predicted groundwater levels of the optimal estimated heterogeneous α field and the observed groundwater levels of the real aquifer, it was found that the correlation was higher than 0.99. Therefore, the HT can be used to obtain the optimal estimated heterogeneous α field in the artificial island.

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