Tectonomagnetic Effects in the Tajikistan's Seismic Regions

Observations of local variations of the geomagnetic field in the seismic regions of Tajikistan during the last two decades exhibit regular anomalies prior to earthquakes with a magnitude of 5.0 or greater. These anomalies may be a valuable predictive tool, and important step forward in earthquake hazard mitigation. Four main types of anomalies have been found, depending on how far they are from the epicentral zone; namely in the focus, near, intermediate or far zone. Analyses of the characteristics of the anomalies have been carried out in terms of the piezomagnetic and electrokinetic mechanisms. The dominance of electrokinetic effects in the generation of tectonomagnetic anomalies is suggested by: (1) a phase delay effect in the local geomagnetic field from the far to the near zone; (2) coincidence of the main earthquake shock with the time when the anomaly begins to return to the background level; (3) relatively low magnetic properties of rocks in the region of observation; and (4) detection of tectonomagnetic signals from the deep crust, below the active magnetic layer.

earthquake prediction, tectonomagnetism, rock magnetism, electrokinetics