Groundwater level changes induced by the 2011 Tohoku earthquake in China mainland

Water-table and discharge changes associated with the 2016–2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers

“…8 Epicentral distance (horizontal axis) vs the discharge changes, expressed as a percentage of the pre-event period mean discharge (left vertical axis) and the water level changes (right vertical axis). Torbidone spring (S5), whose ratio to the pre-event discharge would be infinite (as the spring was dry prior to the earthquake) is marked by an asterisk at water-level changes affecting, in a more permanent way, groundwater flow, is also well described in Yan et al (2014). Whereas the mechanism for explaining the first type of effects is substantially accepted as being transient oscillations due to crustal dynamic poro-elastic deformation in an aquifer during the passage of seismic waves (Rexin et al 1962;Kitagawa et al 2006;Yan et al 2014), the cause of permanent offsets, corresponding to sustained changes, is still debated.…”

“…The effects of earthquakes on groundwater are commonly divided into Btransient oscillations^ (Cooper et al 1965) and Bsustained offset^, which include abrupt rises or falls and sustained gradual rise lasting for several days after the shock (Roeloffs 1998;Yan et al 2014). The most frequent consequences of earthquakes are spring and river discharge increase and water-table rise, which are generally attributed to four general classes of possible explanations: (1) co-seismic static strain increases pore pressure that may contribute to change permeability (e.g.…”

Earth's free oscillations excited by the 2011 TohokuMw9.0 earthquake detected with a groundwater level array in mainland China

“…At 85 out of 216 well sites, maximum amplitude water level oscillations up to 3 m were recorded during the passage of the seismic waves (Yan et al 2014). From these 85 wells, we selected 43 sites for this study ( Fig.…”

“…The amplitudes of the water level oscillations at different sites varied greatly. The maximum amplitude during the passage of the first surface wave was 3 m, with a mean value of Yan et al (2014), where the reader can find additional information about the well-aquifer systems as well as the tidal admittance of each well.…”

“…Before frequency estimation, tidal effects were removed in all 43 wells as in the previous paper (Yan et al 2014). For 27 wells with barometric records, the local barometric effects were corrected (Zürn & Widmer 1995;Zürn & Wielandt 2007;).…”