Groundwater trace elements change induced by M5.0 earthquake in Yunnan

Abstract

Geochemical compositions changes in groundwater in response to earthquakes have been documented for decades, and most such studies have documented the changes in major ions or geochemical gases (e.g., Radon). Changes in trace elements, however, have received less attention. In this paper, we collected groundwater samples from a wellbore in Yunnan Province weekly and analyzed both the major and trace chemical compositions from February 2018 to September 2018. Combined with well water level records, we found that the August 2018 Tonghai M5.0 earthquake caused changes in both water levels and trace elements but caused no significant changes in the stable isotope and major ions. Such a response indicates that trace elements are more sensitive to crustal strain than are the major elements and isotopes. And We considered that earthquake-induced shaking caused a breach in the hydraulic barrier of the isolated reservoir that led to the mixing of water with low concentrations of trace elements as the mechanism to explain the coseismic response. This study demonstrate that some trace elements are more sensitive to earthquake strain than the commonly used chemical constitutents and that trace element monitoring should considered to be a priority in the future to provide a complete assessment of the sensitivity of different chemical constitutents to earthquake stresses.