Pre‐Earthquake Observations and Their Application in Earthquake Prediction in China

Developments in observing and interpreting pre-earthquake phenomena in mainland China are summarized in this paper. The investigated pre-earthquake phenomena include changes in crustal deformation and seismicity, as well as geoelectric, geomagnetic, and groundwater properties. These phenomena are related to crustal deformation changes in and near seismogenic zones prior to an earthquake mainshock. Some general characteristics of pre-earthquake phenomena are listed below, based on case studies of earthquakes that have occurred in mainland China in recent decades. Pre-earthquake phenomena display two different patterns of temporal changes: gradual changes over several months or years and rapid changes over a few days or months. Significant variations in pre-earthquake phenomena usually occur prior to large earthquakes. The pre-earthquake phenomena can be characterized by the amplitude and duration of the anomalous changes, as well as by the spatial and temporal distribution of these changes. Pre-earthquake phenomena are usually observed close to the epicenters of mainshocks. The pre-earthquake phenomena associated with three earthquakes that occurred along the southeastern margin of the Tibetan Plateau in recent years are re-examined. Retrospective studies show that, although preliminary mechanical models provide possible physical explanations for these pre-earthquake phenomena, it is very difficult to use these models to predict earthquakes.