Coseismic Water Level Research Articles

Effects of wellbore and skin zone on co-seismic water level Responses: A numerical study

Effects of wellbore and skin zone on co-seismic water level Responses: A numerical study

Long‐ and Short‐Term Effects of Seismic Waves and Coseismic Pressure Changes on Fractured Aquifers

AbstractTwo adjacent groundwater wells on the North China Platform are used to study how earthquakes impacted aquifers. We use the response of water level to solid Earth tides to document changes after earthquakes and how aquifer and fracture properties recovered to pre‐earthquake properties. We consider two models for the phase and amplitude of water level response to the lunar diurnal (O1) and semidiurnal (M2) tides: a leaky aquifer model, and a model in which fracture orientation determines the response. In the leaky aquifer model, changes arise from changes in permeability and storage; in the fracture model, changes are due to changes in apparent orientation of transmissive fractures. Responses in one well are best explained by the leaky aquifer model, and can explain the large amplitude coseismic water level and permeability changes and the non‐recoverable changes after the largest earthquake. Responses in the other well are consistent with the fracture model and show little coseismic change in water level but changes in apparent fracture orientation. Larger ground motions lead to larger coseismic water level changes and longer recovery times. We propose that the well in the more permeable and shallow aquifer has less variable pore‐pressures around the well. Larger coseismic strains from water level changes may enable longer‐lasting changes in aquifer properties. We conclude that relatively high permeability aquifers are less susceptible to impacts from seismic waves, and thus have small changes in water levels and hydrogeological properties.

Persistent groundwater reduction induced by dynamic stresses from the 2019 Ridgecrest earthquake observed within a fractured aquifer near Ash Meadows, Nevada, USA

Groundwater observations in Ash Meadows, Nevada are dedicated to protect its unique ecosystem and to manage groundwater resources. The groundwater levels are sensitive to natural factors such as earth tides and earthquakes, allowing us to study dynamic hydrologic properties. During the 2019 M6.4 and M7.1 Ridgecrest earthquakes, Ash Meadows groundwater levels declined in the fractured carbonate aquifer by 7-9 cm, whereas no coseismic groundwater level response was observed in the overlying (∼280 m) alluvial aquifer. We analyzed the static and dynamic stresses produced by the earthquake, and found static stresses should have produced only coseismic water level increases in the Ash Meadows region. At the same time, dynamic stresses were large enough to induce coseismic water level response and are likely the driving force for groundwater level reductions in the carbonate aquifer. Although tidal analysis does not show an observable long-term change in hydraulic parameters, we observed a temporary diffusivity enhancement in the 6 days following the M6.4 foreshock. In addition, we did not observe a postseismic recovery of water level in the carbonate aquifer. Instead, a subsequent 2-year observation of water levels indicates a persistent decline at a rate of 1.7−4.6×10−5 m/day, which is in direct contrast to a generally increasing water level before the earthquake. As of August 2021, water levels in the carbonate aquifer have declined between 1.4-3.7 cm since the earthquake. Persistent water level declines induced by the passage of seismic waves may modify aquifer properties in the short (days) and long-term (months to years). High resolution groundwater monitoring is needed to better understand the postseismic response in hydrologically sensitive aquifers such as Ash Meadows.

Multiple mechanisms of coseismic water level changes at the Rongchang well in a seismically active area in China

We examined water level data at the Rongchang (RC) well in the Rongchang natural gas field in China's Sichuan Basin from November 2007 through 2019, where injection-induced seismicity with a magnitude of up to 5.2 has been reported. Coseismic water level changes caused by earthquakes from 3 km to 3500 km away, as well as changes in water temperature, provide a good opportunity to systematically study the mechanisms underlying the response of water level to earthquakes. Among 41 ML ≥ 3.0 local earthquakes, 20 events exceeded the magnitude-distance threshold for the water level to change. Eleven events caused water levels to rise, and only one earthquake led to a decrease in water level. For the 22 distant earthquakes with a seismic energy density greater than the threshold of 0.0017 J/m3, ten events caused rises in the water level and only the MW 7.9 Wenchuan Earthquake caused a temporary, but large, decrease in water level. In total, eight local events and 11 distant events, which were expected to cause coseismic water level changes, actually resulted in no changes. The findings imply that an earlier sizable earthquake may decrease the sensitivity of the well for a certain period of time (approximately two months). The dominant mechanisms of coseismic water level changes in response to near-, mid-, and far-field earthquakes are different. For near-field earthquakes, the drop in coseismic water level is governed by the combined effects of static strain changes and the release of trapped gas bubbles due to the strong vibration of seismic waves in the aquifer; however, only static strain changes are dominant after mid-field earthquakes. For far-field earthquakes, the dominant mechanism is aquifer softening due to growth of gas bubbles in the groundwater that is associated with weak and low frequency seismic shaking of passing surface waves.

Describing coseismic groundwater level rise using tank model in volcanic aquifers, Kumamoto, southern Japan

The change of groundwater levels after the 2016 Mw 7.0 Kumamoto crustal earthquake was evaluated using a simple conceptual hydrological model in an attempt to show the presence, intensity, and probable mechanism of water level rise observed in Kumamoto where a comprehensive observation-well network exists. A tank model was applied to verify 16 wells in the study field. In the model groundwater levels were first calibrated for the periods in ca. 2 years before the main shock using several hydrological parameters including precipitation, evapotranspiration, water recharge and discharge, and artificial recharge by irrigation. Water levels were then simulated by extrapolating this law of water fluctuating patterns for ca. 2.5 years after the main shock of the earthquake, without considering hydrogeological changes due to the earthquake. A difference in groundwater levels between observation and simulation results yields a degree of coseismic water level rises for each well. The coseismic abnormal water level increase was calculated to be ~11 m in 4–5 month after the main shock and was most significantly on the western slope of the Aso caldera rim mountains. The spatial distribution of the coseismic water increases clarified that the most dominate increasing anomalies prevail at mountain feet surrounding the plains, suggesting the occurrence of coseismic mountain water release resulting in the rise of water levels in downslope aquifers. Identified coseismic water level increases still continue up to 2.5 years after the earthquake, probably because changes in hydrogeological properties in mountain aquifers, i.e., permeability, are still sustained. Our forecasting water recovering trends require ca. 3.5–5 year after the earthquake for complete recovery to the original conditions. We demonstrated that our approaches are capable of describing coseismic water level changes and could potentially be applied to other fields.

Comparison of aquifer parameters inferred from water level changes induced by slug test, earth tide and earthquake – A case study in the three Gorges area

Hydraulic conductivity plays an important role in groundwater systems, but the estimation of hydraulic conductivity has many difficulties (the costs, feasibility and the scale-dependent results). In this study, we compared the hydraulic conductivity inferred from the conventional method (slug test) and the natural perturbation methods (tidal response and post-seismic water level recovery methods) at two confined wells, DJP well and MP well. The results show that the hydraulic conductivities estimated by the conventional method and the natural perturbation methods deviate somewhat from each other. The reason for the difference in hydraulic conductivities inferred from three methods is the variations of wellbore skin. By analyzing the uncertainty of estimation, we conclude that the different assumptions of the models cause inherent uncertainty and that the parameter uncertainty is secondary. The calculation results of these methods represent the different scales of the aquifer properties: 5–10 m for the slug test and 10–25 m for the tidal response and the post-seismic water level recovery methods, averaged by the hydraulic properties of the fault zone. The calculation errors of the three methods are 25% for the slug test, less than 10% for the tidal analysis and larger than 10% for the third method. Based on these comparisons, we conclude that the tidal response method is the most favorable way to infer aquifer parameters in this study. Both the tidal response and post-seismic water level recovery method provide a way to estimate aquifer properties as well as the mechanism of the co-seismic water level responses.

Different coseismic groundwater level changes in two adjacent wells in a fault-intersected aquifer system

Previous studies have investigated many cases regarding changes in well water level and attributed differences in the coseismic water level responses to various hydrogeological conditions. However, most of these studies often fail to provide insights into the responses of different portions of one groundwater system because the boreholes in question are usually located in different hydrogeological units with no hydraulic communication. This paper analyzes coseismic and postseismic variation characteristics of the water levels of two adjacent observation wells located near the same fault zone and separated by a distance of approximately 2 km. Well X10 resides in the fault zone and is indirectly connected to the aquifer, whereas Well X11 directly penetrates into the aquifer. Based on the coseismic static strain, seismic energy density and variation in well water level response to earth tides before and after earthquakes, this research investigates the effects of faults on coseismic well water level responses. The results show that under the effects of static compressive stresses, wells X10 and X11 present opposite water level responses due to the presence of the fault. After the earthquake, the water levels in both wells are elevated due to the increased aquifer permeability induced by the earthquake. Nevertheless, because of the fault, the rate of increase of the postseismic water level in Well X10 is obviously lower than that of Well X11. A seismic energy density analysis shows that only three near-field earthquakes with energy densities greater than 10−3 J/m3 can simultaneously trigger the elevation of coseismic water levels in wells X10 and X11. This paper concludes that the oscillation elevation of the coseismic water levels in wells X10 and X11 should be mainly attributed to the increased aquifer permeability. However, the mechanisms underlying this change are quite complex and cannot be explained by a single mechanism, and the increased permeability may be correlated to various factors, such as the coseismic static strain, seismic energy density and borehole condition.

Characteristics of a Sensitive Well Showing Pre-Earthquake Water-Level Changes

Water-level data recorded at a sensitive well next to a fault in central Japan between 1989 and 1998 showed many coseismic water-level drops and a large (60 cm) and long (6-month) pre-earthquake drop before a rare local earthquake of magnitude 5.8 on 17 March 1997, as well as 5 smaller pre-earthquake drops during a 7-year period prior to this earthquake. The pre-earthquake changes were previously attributed to leakage through the fault-gouge zone caused by small but broad-scaled crustal-stress increments. These increments now seem to be induced by some large slow-slip events. The coseismic changes are attributed to seismic shaking-induced fissures in the adjacent aquitards, in addition to leakage through the fault. The well’s high-sensitivity is attributed to its tapping a highly permeable aquifer, which is connected to the fractured side of the fault, and its near-critical condition for leakage, especially during the 7 years before the magnitude 5.8 earthquake.

EFFECTS OF THE JANUARY 30, 2016, Mw=7.2 ZHUPANOVSKY EARTHQUAKE ON THE WATER LEVEL VARIATIONS IN WELLS YUZ-5 AND E-1 IN KAMCHATKA

This paper describes the water level variations in wells YuZ-5 and E-1 inKamchatkaduring the Zhu­panovsky earthquake that occurred on January 30, 2016 (M w =7.2, Н =180 km). The distances from the Zhupanovsky earthquake epicenter to wells E-1 and YuZ-5 were 70 and 80 km, respectively. In well YuZ-5 , the water level raised by 9.4 cm during 45 minutes after the seismic wave arrival. This effect was caused by a combination of a co-seismic rise in the water level due to the volumetric compression of the water-bearing rocks during fracturing in the earthquake source and an impulse increase in the fluid pressure near the wellbore during the seismic shocks. We estimated the amplitude of the coseismic water level increase (D h =7.3 cm) and the strain value resulting from the volumetric compression of the water-bearing rocks, which is consistent with the estimated value of the coseismic volumetric deformation in the area of the well at the depth of 500m: D 1 = –4.5×10 –8 . This estimation was based on the model of the dislocation source in the homogeneous isotropic elastic half-space with the parameters of the Zhupanovsky earthquake focal mechanism. After the earthquake, the water level dropped for three months at an amplitude of about ~40 cm. In order to estimate the radius of the well sensitivity to the pressure drop source, we used the model of water level lowering that followed the pressure drop in the aquifer at a distance to the well as a result of the improved filtration properties of the water-bearing rocks after the seismic shocks. The estimated radius of the well sensitivity, R is 450 m. For 3.5 months before the Zhupanovsky earthquake, ~20 cm increase in the water level was observed, which is anomalous in comparison with the average seasonal variations of the water level, as shown by the long-term observations. In our opinion, such a rise in the water level occurred in the process of the earthquake preparation, and can thus be viewed as its precursor. In well E-1, a sequence of water level changes manifested a hydrogeodynamic precursor: the water level dropped at an increased rate for 21 days before the earthquake, and raised at an amplitude of 3.7 cm during one month after the earthquake. The hydrogeodynamic precursor detected in real time gave grounds for forecasting a highly probable strong earthquake at a distance of up to 350 km from wells E-1 within a month. This forecast was reported to the Kamchatka Branch of the Russian Expert Council (KB REC) on January 21, 2016. The Zhupanov­sky earthquake occurred on January 30, 2016, and its magnitude, time and location correlated with the prediction. The case of this earthquake shows that the Kamchatka Branch of the Federal Research Center ‘Geophysical Survey of RAS’ has the system of water level observations and data processing, which is capable of diagnosing (close to real time and retrospectively) different types of hydrogeoseismic variations in the water level in wells in case of strong seismic events, and detecting the hydrogeodynamic precursors of strong earthquakes.

Coseismic water level changes induced by two distant earthquakes in multiple wells of the Chinese mainland

Coseismic water level oscillations, or step-like rises and step-like drops were recorded in 159 wells throughout the Chinese mainland due to the 2015 Nepal Mw 7.8 earthquake, and 184 wells for the 2011 Japan Mw 9.0 earthquake. The earthquake magnitude, and the associated dynamic stresses, has positive roles in both the sensitivity of water level to earthquake induced change, and the amplitude and duration of resulting coseismic water level changes. Wells whose water levels are sensitive to Earth tides have high potential to response to earthquakes. Polarities of step-like changes (rises or drops) are locally controlled and spatially variable, with artesian wells generally recording water-level rises. Permeability enhancement was assessed as a mechanism responsible for step-like changes by analyzing the tidal phase responses. Permeability variations are inferred for 17 out of 95 wells with step-like changes during the Nepal earthquake and for 32 out of 105 wells following the Japan earthquake; however, only 6 wells have permeability variations after both earthquakes.

Co-seismic water level changes in response to multiple large earthquakes at the LGH well in Sichuan, China

We examined the water level data at the LGH well in Sichuan, China, from December 2007 to July 2015 and their responses to multiple large earthquakes with seismic energy densities greater than 10−4J/m3. Co-seismic water level declines were observed in response to eleven earthquakes out of twelve in the farfield, and co-seismic water level increase was observed in one nearfield case. The water level declines in the farfield showed a linear relation with the common logarithm of the seismic energy densities, whereas the water level increase in the nearfield fell away from this relation, indicating that the farfield responses and the nearfield response were produced by distinct mechanisms. We used the phase shift of tidal responses as a proxy for permeability and found that permeability enhancements were observed both in the farfield and nearfield. The co-seismic water level declines in response to the distant earthquakes could be explained by permeability enhancements caused by the passage of seismic waves through the mobilization of colloidal particles; the co-seismic water level increase in response to the nearfield case could be caused both by the compression of the static stress and by the seismic waves.

Mechanism of co-seismic water level change following four great earthquakes – insights from co-seismic responses throughout the Chinese mainland

We analyze the co-seismic groundwater level responses to four great earthquakes recorded by China's network of groundwater monitoring wells. The large number of operational wells (164 wells for the 2007 Mw 8.5 Sumatra earthquake, 245 wells for the Mw 7.9 Wenchuan earthquake, 228 wells for the Mw 9.0 Tohoku earthquake and 223 wells for 2012 Mw 8.6 Sumatra earthquake) and co-seismic responses provide an opportunity to test hypotheses on mechanisms for co-seismic water level changes. Overall, the co-seismic water level responses are complex over large spatial scales, and there is great variability both in the sign and amplitude of water level responses in the data set. As shown in previous studies, permeability change, rather than static strain, is a more plausible mechanism to explain most of the co-seismic responses. However, we find through tidal analysis of water level responses to solid Earth tide that only one third of these wells that showed a sustained post-seismic response can be explained by earthquake-induced permeability change in aquifers, and these wells had sustained (>30 days) water level changes. Wells that did not show sustained changes are more likely affected by permeability changes only immediately adjacent to the wellbore.

Coseismic water-level changes in a well induced by teleseismic waves from three large earthquakes

Three large earthquakes (the 2007 Mw 8.4 Sumatra, the 2008 Mw 7.9 Wenchuan, and the 2011 Mw 9.0 Tohoku) induce coseismic water-level increment at far fields (epicentral distances>1000km) in the Fuxin well located in the Fuxin City, northeastern China (the well with the observation of both water levels and volume strains). A comprehensive analysis for the mechanism of far-field coseismic water-level changes is performed by analyzing the in-situ permeability, Skempton's coefficient B, and with the broadband seismograms from a nearby station. We observe an undrained compaction with a decreasing permeability induced by the shaking of teleseismic waves in the far field. Shaking by teleseismic waves can induce compaction or dilatation in the aquifer of Fuxin well; is able to enhance permeability and thus build a new pore-pressure equilibrium system between the Fuxin well and the nearby Sihe reservoir (150m away from the Fuxin well). The resulting interstitial fluid flow across the region increases coseismic water levels in the aquifer of Fuxin well.

Analysis of the Water Level Fluctuation in Koyna-Warna Region, India

ABSTRACT Koyna region in India is known to be the largest case of the Reservoir Triggered Seismicity (RTS) in the world with Magnitude 6.3 (M 6.3) earthquake in 1967. The region is seismically active even after forty five years with occurrences of earthquakes up to M 5.0. The porous crustal rocks of Koyna – Warna region respond to changes in the prevailing stress / strain regime. These changes induce variations in the water level in bore wells before; during and after an earthquake and their study can help in understanding the earthquake genesis in the region. In this work the observed water levels in the bore wells have been analyzed and found the co-seismic water level changes in some wells. The earthquake on 14 th March 2005 with M 5.1 in Koyna – Warna region has been studied by using wavelet transformations and the results reveals the significant co-seismic changes in some of the bore wells. The Ukalu well has showed the maximum change in the water level since the epicenter is close to the well. The focal mechanism and the distance of the epicenter play important role in the variation of the water level fluctuations.

Tidal response variation and recovery following the Wenchuan earthquake from water level data of multiple wells in the nearfield

Tidal response variation and recovery following the Wenchuan earthquake from water level data of multiple wells in the nearfield

Co-Seismic Groundwater Level Changes Induced by the May 12, 2008 Wenchuan Earthquake in the Near Field

The large scales of co-seismic water level changes in mainland China were observed in response to the tragic 2008 Ms 8.0 Wenchuan earthquake. To better understand the mechanism of these hydrogeological phenomena, groundwater-level data at 17 confined wells, with an epicentral distance of <500 km, were collected. We compare the static strain predicted by dislocation theory with the volumetric strain calculated by the tide effect of the groundwater based on poroelastic theory. The results show that the sign of the co-seismic groundwater level change is consistent with the sign predicted by dislocation theory. Additionally, the magnitude of the strain calculated by the two methods is also concordant in half of the wells. In the rest of the wells, the strains inversed from the groundwater level are one or two orders of magnitude larger than the fault dislocation model. These wells mostly have an epicenter distance larger than 300 km; therefore, the dynamic stress induced by the seismic wave may be responsible for the co-seismic water level changes in these wells. According to these results, we roughly estimate that the effect range of the static stress is approximately 300 km for the Wenchuan earthquake, and the dynamic stresses dominate beyond this epicenter distance. In addition, geological and hydrogeological conditions and other mechanisms may be responsible for these changes.

Mechanism of Different Coseismic Water-Level Changes in Wells with Similar Epicentral Distances of Intermediate Field

Water-level changes at different monitoring stations are observed during the Wenchuan earthquake ( M S 8.0) in the Chinese mainland. In the intermediate field, we observed coseismic water-level changes of different amplitude in wells with similar epicentral distances. In order to study the mechanism of those coseismic water-level changes, we calculated the static strain change with the Okada dislocation model (Okada, 1992; Lin and Stein, 2004; Toda et al. , 2005). By comparing the calculated coseismic water-level change based on the poroelastic theory with the observed water-level change, we can judge whether the poroelastic theory can be applied to the aquifer of the well. From our research, we find the poroelastic theory can be applied to the area with epicentral distance≲1.5 fault rupture length. Bearing this in mind, we find that when the water-level change of those wells can be explained by the poroelastic theory and that the difference of the water-level change in wells with similar epicentral distances is mostly related to the difference of Skempton’s coefficient B . Otherwise, the water-level change may be induced by the transition of the seismic waves because it is usually larger than the one induced by the undrained dilatation and consolidation, and changes more gradually.

Analysis of Coseismic Water-Level Changes in the Wells in the Koyna-Warna Region, Western India

Abstract We test the hypothesis that coseismic water-level changes in wells are proportional to coseismic volumetric strain by analyzing available data from the Koyna–Warna region of western India. A total of 18 cases of water-level changes have been reported at ten wells corresponding to six earthquakes of M ≥4.3 that occurred in the region from 1997 to 2005. Out of these, clear unambiguous steplike coseismic water-level changes have been observed in ten cases at five confined wells. We used basic poroelastic theory to simulate volumetric strain and corresponding water-level changes and find that all cases show consistency in sign between reported coseismic water-level changes and simulated volumetric strain. All confined wells with high strain sensitivity that are located near earthquake epicenters show good agreement in magnitude between simulated and reported volumetric strain, thereby supporting this hypothesis.

Characteristics of coseismic water level changes at Tangshan well for the Wenchuan MS8.0 earthquake and its larger aftershocks

Coseismic water level changes which may have been induced by the Wenchuan MS8.0 earthquake and its 15 larger aftershocks (MS≥5.4) have been observed at Tangshan well. We analyze the correlation between coseismic parameters (maximum amplitude, duration, coseismic step and the time when the coseismic reach its maximum amplitude) and earthquake parameters (magnitude, well-epicenter distance and depth), and then compare the time when the coseismic oscillation reaches its maximum amplitude with the seismogram from Douhe seismic station which is about 16.3 km away from Tangshan well. The analysis indicates that magnitude is the main factor influencing the induced coseismic water level changes, and that the well-epicenter distance and depth have less influence. MS magnitude has the strongest correlation with the coseismic water level changes comparing to MW and ML magnitudes. There exists strong correlation between the maximum amplitude, step size and the oscillation duration. The water level oscillation and step are both caused by dynamic strain sourcing from seismic waves. Most of the times when the oscillations reach their maximum amplitudes are between S and Rayleigh waves. The coseismic water level changes are due to the co-effect of seismic waves and hydro-geological environments.

Implications of coseismic groundwater level changes observed at multiple-well monitoring stations

SUMMARY Earthquake-related groundwater level changes have been recorded by a dense network of monitoring well stations in Taiwan. At most multiple-well stations, the direction and magnitude of coseismic water level changes vary in wells of different depths. Comprehensive water level data recorded in 209 wells in the vicinity of the seismogenic fault during the 1999 M L7.3 earthquake demonstrate a preliminary 3-D distribution of coseismic changes. The largest coseismic rise at a station observed typically in a confined gravel aquifer indicates the association of the magnitude of coseismic change with characteristics, rather than depth, of the aquifer. The variation of coseismic changes in the vertical direction implies possible inconsistency between the observed water level changes and the volumetric strains calculated from simple dislocation models. At a given hypocentral distance, the coseismic change in the footwall of the ruptured segment of the fault was much greater than that of the unruptured segment. This phenomenon suggests that fault displacement plays an important role in the generation of coseismic changes. While hypocentral distance correlates well with coseismic rise or fall in the vicinity of the ruptured seismogenic fault, poor correlation is found for coseismic change further from the earthquake epicentre.