Sensitivity of hydraulic properties to dynamic strain within a fault damage zone

Several experiments and field observations have demonstrated seismic waves‐induced permeability increases. However, a few experiments have revealed significant decreases in the permeability of fractured sandstone after shaking produced by dynamic stresses. In this paper, we analyze the tidal responses of the water level in two wells (Junan and Dingyuan) situated on and near, respectively, the Tan‐Lu fault in China. The results sampled by a single well indicate that seismic waves could both increase and decrease the permeability. In addition, our results indicate that the earthquakes that decreased the permeability in a single well were distributed in certain azimuthal zones. Given the azimuthal distribution of distant earthquakes, the observed permeability decrease could be attributed to the seismic wave‐induced clogging of fractures that compose the flow paths in the shallow crust. Our research contributes to an enhanced overall understanding of the effects of earthquakes on the permeability of the shallow crust.

Section: Discussionmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seismic Waves Could Decrease the Permeability of the Shallow Crust

Shi

Liao

et al. 2019

“…Many previous studies document that fault zone properties will change under the static and dynamic stresses produced by earthquakes (Kinoshita et al, ; Kitagawa et al, ; Shi et al, ; Xue, ), which will cause changes in subsurface transport (Wang et al, ). Such changes can be captured and observed through monitoring the variation in physical and chemical parameters in groundwater wells and springs (Manga & Rowland, ; Yan et al, ). Thus, monitoring the hydrological changes in fault zones provides a way to obtain the spatial and temporal changes of fault zone properties in response to earthquakes and other tectonic activities.…”

Section: Introductionmentioning

confidence: 99%

Fault Zone Permeability Decrease Following Large Earthquakes in a Hydrothermal System

Shi

Zhang

Yan

et al. 2018

Self Cite

Seismic wave shaking‐induced permeability enhancement in the shallow crust has been widely observed. Permeability decrease, however, is seldom reported. In this study, we document coseismic discharge and temperature decrease in a hot spring following the 1996 Lijiang Mw 7.0 and the 2004 Mw 9.0 earthquakes in the Balazhang geothermal field. We use three different models to constrain the permeability change and the mechanism of coseismic discharge decrease, and we use an end‐member mixing model for the coseismic temperature change. Our results show that the earthquake‐induced permeability decrease in the fault zone reduced the recharge from deep hot water, which may be the mechanism that explains the coseismic discharge and temperature responses. The changes in the hot spring response reflect the dynamic changes in the hydrothermal system; in the future, the earthquake‐induced permeability decrease should be considered when discussing controls on permeability.

“…It is well known that earthquakes can result in changes to the well water level or spring flow (Rojstaczer et al, ; Skelton et al, ; Manga & Wang, ; Shi & Wang, ), with these changes reflecting interactions between tectonic activities and hydrological systems (Manga et al, ; Shi, Wang, et al, ; Wang & Barbour, ). Studies have shown that static or dynamic stresses generated during earthquake genesis and occurrence can cause permeability changes to fault zones (Kinoshita et al, ; Kitagawa et al, ; Shi et al, ), which in turn cause changes in groundwater flow conditions (Wang et al, ), thus making it possible to effectively obtain permeability changes of fault zones by monitoring changes in the well water level or the spring flow in faults (Manga & Rowland, ; Yan et al, ).…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Permeability Changes along a Fault Zone Caused by the Xingwen M5.7 Earthquake in SW China

Sun

Xiang

2019

Earthquakes can change permeability. Continuous monitoring of the response of water level to solid Earth tides or changes in barometric pressure provides an opportunity to document how earthquakes influence permeability. Here we document spatial variations in changes in a fault zone in SW China. The response of the water level to barometric pressure and the Earth tide in four observation wells was used to calculate the relative changes in permeability at different locations on the fault before and after the Xingwen M5.7 earthquake. The results revealed that the earthquake resulted in a spatial heterogeneity in permeability changes along the Huarongshan fault. Moreover, permeability changes in the horizontal and vertical directions differed from one another at the same well location; that is, there was anisotropy at each location. These findings will help to enhance the understanding of earthquake-induced changes of permeable fault structure and fault segment deformation.Plain Language Summary Earthquakes can increase and sometimes decrease the permeability of crustal materials and fault zones. Most of these reports have been based on analyses of the response of the well water level to the Earth tide. In this study, characteristics of the permeability change in the Huarongshan fault before and after the Xingwen M5.7 earthquake were obtained based on the responses of the characteristic parameters of well water level to barometric pressure in the fault zone. The results revealed that the earthquake-induced permeability changes were spatially heterogeneous at different locations and anisotropic at each location. The relative permeability changes before and after the earthquake do not show a direct correlation with the coseismic response of the well water level. The strategy of simultaneously obtaining the vertical and horizontal permeabilities based on the response of the well water level to the barometric pressure used in this study will provide a new method for analyzing the anisotropy of permeability changes in shallow crustal media.