Advances in seismic fluid geochemistry and its application in earthquake forecasing

Abstract

<p indent="0mm">Earthquakes are one of the most serious natural disasters of the world, with huge potential to cause serious injury and damage to humans and society. Earthquake forecasting, however, still remains a worldwide unsolved problem. The generation and occurrence of an earthquake—Accompanied by material migration, energy transmission and abrupt changes of underground conditions—Can result in the migration and evolution of geochemical elements and isotopes in natural fluids. Active fault zones are not only earthquake-prone areas but also deep fluid overflow channels. The geochemical characteristics of fluids in active faults act as good indicators for tectonic and seismic activities due to their high sensitivities to the changes of stress, temperature and permeability in the crust. The spatial and temporal variations of fluids in the active fault zones are closely related to the deep geological process and as well as the type, scale, and state of the active faults. On the contrary, the state change of an active fault can continue to affect the evolution and migration process of the deep fluids. The close relationship between fluid geochemistry and active faults makes fluid geochemistry not only an important role in earthquake forecasting but also an effective means to explain the changes of materials and conditions that take place during an earthquake. Before the occurrence of an earthquake, the stress and strain can lead to complex changes of chemical elements and isotopes in subsurface water, gas, soil and/or other media, that is, seismic fluid geochemistry anomalies. Therefore, in active fault zones or seismically active areas, monitoring the fluid geochemistry in these surface media and effectively identifying anomalies related to earthquakes have been identified as promising methods for earthquake forecasting. In recent years, seismic fluid geochemistry has been widely used to forecast earthquakes around the world due to its comparatively low costs and the advantages of its timeliness, simplicity, and convenience. Furthermore, with the accumulation of observation data, improved data processing methods and summaries of earthquake cases, more and more fluid geochemistry anomalies are being detected before the occurrence of earthquakes, particularly that of big earthquakes. As a result of the early detection of geochemistry anomalies, some earthquakes have even been successfully predicted. In addition, new analytical techniques play a more significant role in studies of the mechanism of earthquake precursors and seismic physical processes. However, most earthquake predictions are currently based on phenomenon correspondence and/or empirical statistics, and the lack of research on the genetic mechanism of seismic fluid geochemistry anomalies leads to difficulties in the further application of this method. As such, there remains significant room for improvement for the construction of a prediction model based on seismic fluid geochemistry. In this paper, the recent research progress of seismic fluid geochemistry in the field of earthquake forecasting is summarised and combined with our research results and insights to provide guidance for future works in earthquake forecasting methods.