Seismic Waves Could Decrease the Permeability of the Shallow Crust

Abstract

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.

Earthquakes and extreme rainfall induce long term permeability enhancement of volcanic island hydrogeological systems

“…Nevertheless, quantifying relationship between the intensity of ground motion and hydrological or hydrogeological responses remains partly unclear. On one hand, a clear correlation between peak ground velocity (PGV) and a permeability change is highlighted in California 9 , but in another hand this correlation was not observed by others studies 27 , 60 – 62 . Threshold effects have also to be considered, as permeability changes should occur mainly above a threshold value 63 .…”

“…Aquifer transmissivity can be determinated from earth tide analysis 9 , 17 , 27 , 28 , 38 , considering the time lag (phase shift) between the tidal dilatation of the aquifer and the water level response in the well 6 . Geologic or topographic heterogeneity may affect the tidal response of an area 39 , but these effects did not vary over the duration of our study 10 , and should not affect the phase lag evolution.…”

“…The permeability increase highlighted over the last twelve years is corroborated over geological ages thanks to the statistical analysis of existing pumping tests data in comparable aquifers of the island. Since we highlight over twelve years that permeability globally increase over the period, but that some earthquakes can also decrease permeability, it follows that permeability decrease should be transient because of: i) the tropical climate with hurricane and extreme rainfall regularly flushing particles and thus unclogging fractures, ii) the possible effect of successive earthquakes (as in 2018), considering that stress/strain from consecutive earthquakes may generate a stronger permeability increase following the second earthquake 54 , and iii) on a long-term scale, earthquakes increasing permeability may be more numerous than earthquakes decreasing permeability, with possible azimuthal 27 and compression/extension effects dependences.…”

“…A decrease in permeability triggered by earthquakes is much less documented 24 – 27 . In this last case, fractures clogging by particles or fine sediments is often involved, with a possible link with earthquake azimuth relative to fracture orientation 27 . Over time, permeability increase and decrease can be observed in the same boreholes 27 .…”

“…In this last case, fractures clogging by particles or fine sediments is often involved, with a possible link with earthquake azimuth relative to fracture orientation 27 . Over time, permeability increase and decrease can be observed in the same boreholes 27 . Lastly, permeability variations not only concern aquifers but also aquitards 18 , 28 whose hydraulic properties increase can have significant environmental consequences, an example is a leak off from polluted subsurface water to underground water.…”