The mine collapse at Lo Tacon (Murcia, Spain), possible cause of the Torre Pacheco earthquake (2nd May 1998, SE Spain)

摘要

On 2nd May 1998, a sudden and rapid collapse occurred in an area of abandoned metal ore mines in La Union (SE Spain). Due to this event, surface subsidence occurred at "Lo Tacon" industrial park resulting in extensive damage to buildings in the affected area. This mine collapse coincided with an earthquake of magnitude 2.4 M_w recorded by seismic stations near the National Geographic Institute of Spain (Spanish acronym, IGN) that situate the epicentre in the town of Torre Pacheco, about 20 km northeast of the city of La Union, at a depth of 2.6 km. The lack of coverage of seismic stations east of Torre Pacheco created uncertainty regarding the precise location of the epicentre which we believe to be reasonable. In this paper, we consider the hypothesis that it was the failure in the mine that triggered the collapse and induced a seismic energy of M_w magnitude equal to the earthquake at Torre Pacheco. The seismic energy of the earthquake came from a percentage of the strain energy stored within the rock (massive grey dolomite) that was released by rupture of a rock volume due to the increase in the roof span when a pillar failed, thus triggering cascading pillar failure (CPF). The results of the study prove that the energy recorded at the Spanish National Geographic Institute (IGN) seismic stations is consistent with the calculated released seismic energy for the mining collapse at Lo Tacon.