Identification of Groundwater Radon Precursory Anomalies by Critical Slowing down Theory: A Case Study in Yunnan Region, Southwest China

Zhiyuan Qiao,Guangcai Wang,Hong Fu,Xiaojing Hu

doi:10.3390/w14040541

Abstract

In this study, we use the critical slowing down (CSD) theory to identify the precursory anomalies of groundwater radon based on the 1000-day continuous data from 8 monitoring stations in Yunnan Province, China during the seismically active period of 1993–1996. The low-frequency and high-frequency information were extracted from raw groundwater radon data to calculate their one-step lag autocorrelation (AR-1) and variance, respectively, in order to identify the precursory anomalies. The results show that the anomaly characteristics can be divided into three categories: sudden jump anomalies, persistent anomalies, and fluctuation anomalies. The highest average seismic recognition rate is 72.78%, based on the high-frequency information’s autocorrelation, while the lowest is 45.08%, based on the low-frequency information’s variance. The crustal activity and the change in hydrogeological conditions are possibly the main factors influencing groundwater radon anomalies in the selected period in the study area. There is a positive correlation between the anomaly occurrence time and epicentral distance when epicentral distance is less than 300 km, which may be related to the seismogenic modes and hydrogeological conditions. This study provides a reference for identifying groundwater radon anomalies before earthquakes by mathematical methods.

Highlights

Received: 19 December 2021Earthquake disasters are important global issues concerning the development of human society, which can often be highly destructive due to the lack of early warning systems [1]
It was first proposed in 1927 that radon anomalies in groundwater were related to earthquakes, but it was not until 30 years later that people collected accurate data showing the change in radon concentrations in groundwater before earthquakes [7,8]
We computed the autocorrelation and variance of high-frequency information and low-frequency information data on groundwater radon for each monitoring well

Summary

Introduction

Received: 19 December 2021Earthquake disasters are important global issues concerning the development of human society, which can often be highly destructive due to the lack of early warning systems [1]. The geochemistry anomalies related to earthquakes are important research directions in the search for earthquake precursors with potential use in earthquake prediction [2]. There are many published studies on the relationship between radon and earthquakes, suggesting that radon has the potential to be a good indicator of the precursory process [6]. It was first proposed in 1927 that radon anomalies in groundwater were related to earthquakes, but it was not until 30 years later that people collected accurate data showing the change in radon concentrations in groundwater before earthquakes [7,8]. It has become a consensus that radon anomalies could be related to earthquakes, it is generally very difficult to identify anomalies because radon

Methods

Results

Discussion

Conclusion