Chapter 5 - Earthquake Precursors

Abstract

This chapter draws attention toward devastating earthquakes. To reduce catastrophic (human and financial) losses, scientists and engineers are trying to develop techniques of predicting future earthquakes. Short-term seismic forecasting is the concept of precursors—events that supposedly precede and indicate oncoming earthquakes. It is believed that an earthquake occurs because the accumulated stresses exceed a certain frictional resistance limit, therefore, if at a particular point, the accumulation of stresses at the fault is detected, then it can be inferred that there is a possibility of an earthquake occurrence. A short-term forecast is important to reduce and mitigate potential damage caused by a large earthquake. Possible precursors are cosmic events, abnormal animal behavior, electrical phenomena associated with earthquakes, crustal movement, stresses, and strains, seismic activity, changes in the velocity ratio of the seismic waves, hydraulic resistivity, hydrodynamics anomalies, and acidity and chemical composition of groundwater, radon concentration in the groundwater and soil air, and changes in the concentrations of various gases.