Earthquakes prime landscapes for typhoon-induced permeability loss

Source abstract

Bedrock aquifers supply drinking water to half the global population, and earthquakes can disrupt this resource for years by changing their permeability. Previous studies proposed several mechanisms to explain coseismic permeability changes but lacked an observational tool to distinguish them; moreover, all assumed an immediate onset. Here, we analyse groundwater and seismic data from eastern Taiwan capturing the responses of the aquifer and the surrounding rock substrate to the 2024 M7.2 Hualien earthquake. Tracking substrate and aquifer responses separately enables us to distinguish permeability changes driven by mechanisms confined to the aquifer from those affecting the entire subsurface. We observe two distinct ways in which earthquakes modify aquifer permeability: coseismic shaking produces immediate permeability increases that co-evolve with substrate changes. Months later, two consecutive typhoons triggered abrupt permeability decreases - an observation unique to the postseismic period. As the substrate remains unaffected by these typhoons, we attribute this response to the combined effect of the earthquake, which increased sediment availability and enhanced infiltration capacity, and typhoon-induced overland flow, delivering the sediment into the aquifer, clogging fractures. Our results demonstrate that large earthquakes can prime landscapes for delayed hydrological disruption, with potentially long-lasting consequences for groundwater supply and landslide susceptibility.