Groundwater Radon in the Taiwan Subduction Zone: A Natural Strain-Meter for Earthquake Prediction (Advances in Geological Science)

This book presents the mechanism of in-situ radon volatilization and outlines the geological requisites to site a radon monitoring well for earthquake warning. A small fractured aquifer under undrained conditions is an effective natural strain meter for earthquake prediction. It shows significant merit on a local basis, and most importantly, the analysis can also be applied globally in subduction zones with similar tectonic settings and physical–chemical relationships. Between 2003 and 2010, anomalous declines in groundwater radon concentration were recurrently recorded at Antung, Taiwan, which are considered as precursory to local major earthquakes. The correlations between radon decline and earthquake magnitude are useful for early warning of local main earthquakes. The book consists of 7 chapters. Chapter 1 presents background information and the objectives of the book. Chapter 2 illustrates the methods of monitoring groundwater radon and a brief review of earthquake prediction research using groundwater radon. Chapter 3 provides the details of anomalous decrease in groundwater radon before the Taiwan Mw 6.8 Chengkung Earthquake of 2003. Chapter 4 provides the description of the mechanism of groundwater-radon volatilization. Chapter 5 shows the recurrent anomalous declines in groundwater radon concentration consistently recorded at Antung, Taiwan, prior to local main earthquakes that occurred between 2003 and 2010. Monitoring groundwater radon in small, unconfined fractured aquifers is explained in Chapter 6, followed by an analysis of correlating precursory declines in groundwater radon, precursory time with earthquake magnitudes for small, confined fractured aquifers in Chapter 7. Preface 6 Acknowledgments 8 Contents 9 About the Author 11 List of Figures 12 List of Tables 17 1 Introduction 18 1.1 Background and Objectives 18 1.2 Organization of the Book 19 References 21 2 Methods of Monitoring Groundwater Radon 22 2.1 Introduction 22 2.2 Collection of Groundwater Samples 23 2.2.1 Single-Phase Groundwater Samples 23 2.2.2 Two-Phase Samples of Geo-Fluids 24 2.3 Determination of Radon Activity 26 2.3.1 Liquid Scintillation Counting Method 26 2.3.2 ZnS Scintillation Counting Method 27 2.3.3 Continuous Measurement of Radon in Groundwater 30 2.4 Radon Distributions in Groundwater Near an Active Fault 31 2.5 Application of Groundwater Radon for Earthquake Prediction Research 33 References 36 3 Anomalous Radon Decline at Antung Hot Spring Before the 2003 Mw 6.8 Chengkung Earthquake 38 3.1 Introduction 38 3.2 Radon Monitoring at Antung Near the Longitudinal Valley Fault 39 3.3 Radon Anomaly Before the 2003 Mw 6.8 Chengkung Earthquake 41 3.4 Criticism of Radon as a Precursor 42 References 44 4 A Physical Mechanism of Groundwater-Radon Volatilization 45 4.1 Introduction 45 4.2 Suitable Geological Conditions 46 4.3 In-Situ Radon-Volatilization Mechanism 47 4.4 In-Situ Volatilization Mechanism for Groundwater-Dissolved Gas 50 References 51 5 Recurrences of Radon Anomalies Precursory to Local Main Earthquakes at Antung Hot Spring 53 5.1 Introduction 53 5.2 Recurrences of Radon Anomalies Observed at Antung D1 Well 55 5.3 Aquifer Transmissivity as a Complementary Earthquake Precursor* 60 5.4 Confirmation of In-Situ Volatilization Mechanism: Ruling Out Hypothesis of Groundwater Mixing* 64 5.5 Favorable Geological Conditions for In-Situ Gas-Bubble Development 64 References 65 6 Anomalous Radon Declines in Small Unconfined Aquifers: Corroboration of Favorable Geological Conditions 67 6.1 Introduction 67 6.2 Geological Settings of Paihe Spring Versus Antung Hot Spring* 68 6.3 Anomalous Radon Declines Before the 2010 Mw 6.3 Jiasian and 2016 Mw 6.4 Meinong Earthquakes: Paihe Spring, Taiwan* 71 6.4 Anomalous Gas Declines Before the 1984 M 6.8 Western Nagano Earthquake: Byakko Spring, Japan 76 References 79 7 Anomalous Radon Declines in Small Confined Aquifers: Evaluation of Global Data 80 7.1 Introduction 80 7.2 Japan: Radon Anomaly Before the 1978 Izu-Oshima-Kinkai Earthquake (M 7.0) 81 7.3 Iceland: Radon Anomaly Before the 1978 Southern Iceland Earthquake (ML 4.3) 85 7.4 Taiwan: Correlations for Earthquake Prediction on the Longitudinal Valley Fault 89 7.5 Future Prospects 95 References 97