Various far-field hydrological responses during 2015 Gorkha earthquake at two distant wells

Abstract

Aquifer hydraulic parameter can change during earthquakes. Continuous monitoring of the response of water level to seismic waves or solid Earth tides provides an opportunity to document how earthquakes influence hydrological properties. Here, we use data of two groundwater wells, Dian-22 (D22) and Lijiang (LJ) well, in southeast Tibet Plateau in response to the 2015 Mw 7.8 Gorkha earthquake to illustrate hydrological implications. The coherences of water level and seismic wave before and after the far-field earthquake show systematic variations, which may confirm the coseismic dynamic shaking influence at high frequencies (f > 8 cpd). The tidal response of water levels in these wells shows abrupt coseismic changes of both phase shift and amplitude ratio after the earthquake, which may be interpreted as an occurrence in the vertical permeability of a switched semiconfined aquifer in the D22 well, or an enhancement unconfined aquifer in the LJ well. Using the continuous short-term transmissivity monitoring, we show that the possible coseismic response for about 10 days and instant healing after 10 days to the causal earthquake impact. Thus, the dynamic shaking during the Gorkha earthquake may have caused the short-term aquifer responses by reopening of preexisting vertical fractures and later healing at epicentral distances about 1500 km.

Changes of Hydraulic Transmissivity Orientation Induced by Tele‐Seismic Waves

“…This process does not require special pore pressure conditions, such as near‐lithostatic pressure. Fracture unclogging is often explicitly invoked to explain changes in permeability produced by dynamic stresses, in the lab (e.g., Candela et al., 2015; Elkhoury et al., 2011; Liu & Manga, 2009; Roberts, 2005) or field (e.g., Brodsky et al., 2003; Huang & Zhang, 2021; Shi et al., 2019; Shi & Wang, 2015; Vittecoq et al., 2020; Wang et al., 2004; Weingarten & Ge, 2014), and could result in changes in the apparent mean orientation of conductive fractures. Over time, particles could reclog narrow apertures connecting fractures (Candela et al., 2014; Kocharyan et al., 2011), which could induce the permeability decrease and recovery to pre‐earthquake values (Liu & Manga, 2009), and also could result in changes in the apparent mean orientation of conductive fractures.…”

Using the Tidal Response of Groundwater to Assess and Monitor Caprock Confinement in CO2 Geological Sequestration

“…More plausible is that the fluid flow oscillations caused by seismic waves alter the interconnectivity and apparent orientation of existing fractures (Figure 12) by either clearing or obstructing pre-existing flow channels [92]. The process of fracture unclogging is frequently cited as a mechanism for permeability variations due to dynamic stresses: this phenomenon has been observed in laboratory settings [95][96][97][98], field studies [77,[99][100][101][102][103][104], and numerical simulations [105], potentially leading to shifts in the apparent direction of hydraulically conductive fractures. The shorter lines indicate the pre-earthquake orientation, while the longer lines indicate the postearthquake orientation.…”

Far‐Field Groundwater Response to the Lamb Waves From the 2022 Hunga‐Tonga Volcano Eruption

“…For examples, the Mw 9.0 Tohoku earthquake resulted in significant WL changes (Sun et al., 2015), while the 2004 Mw 9.1 Sumatra earthquake led to groundwater eruption from a well in the mainland China, reaching a height over 30 m (Yan et al., 2022). Additionally, some studies have shown that the far‐field WL can be disturbed after major earthquakes (Huang & Zhang, 2022; Zhang et al., 2019), as stress acts on the rock strata, causing groundwater to move in and out of boreholes.…”