Investigating a Temperature Increase before and During a Magnitude 8 Earthquake Affecting the Portuguese Territory

Abstract

Historical and registered earthquakes of great magnitude have caused destruction with injuries and deaths in mainland Portugal. This work uses data not yet used to investigate a possible increase of the temperature of the water in the region and possible consequences when materials with different thermal properties are in physical contact. A temporal link between geomagnetic anomalies recorded by Permanent Geomagnetic Observatories and earthquakes detected in the Iberian Peninsula and adjacent regions during the month of February in 1969 was found using data from 3 Observatories located in the Iberian Peninsula. The anomaly recorded on February 27,1969 is due to large alterations in the direction (inclination) of the geomagnetic field and associated variations in the electric field of the atmosphere recorded in Lisbon. The source of the first earthquake filled and registered in the early morning of February 28 was in the Atlantic Ocean. The variations in the geomagnetic inclination, detected in the records, may have led to rotations of the water molecules to align their electric dipoles with the electric field in the region, originating heat release. As consequence, an increase of temperature occurred. The analysis of the arrival times of the first seismic waves at the seismic stations located in Lisbon, Coimbra and Porto (cities located near the Atlantic Ocean at different latitude values) combined with the distances of the cities to the earthquake source, shows different values of the average speed of propagation of the seismic waves. The values found decrease from Porto to Lisbon. Seismic velocity values change with temperature and pressure. As we are talking about the same earthquake, different temperature values found in the last part of the wave paths seems to be responsible for this fact. This means that temperature values at lower latitude values (Lisbon city and earthquake source) are higher. The increase of the temperature values of water contributes to the opening of cracks and faults in the region with the entry of hot water that can reach great depths, increasing the temperature, the volume, and the pressure of the materials. When materials with different values of thermodynamic properties like specific heat, thermal conductivity and thermal expansion coefficient are in physical contact, the heat received from the water can originate perturbations like pressure gradients of thermal origin whose value can increase causing rupture of the materials. The presence of water with elevated temperatures in deep regions can also change the velocity of chemical reactions with heat release, increasing the described effect.