ANOMALOUS OF LOW-VELOCITY ZONE, THERMAL WATER AND SEISMICITY IN THE ELBASAN-DIBRA FAULT ZONE

Abstract

A detailed investigation of the hypocenter distribution beneath Elbasani, Albania, reveals a NE-SW-trending linear alignment of seismicity within the Elbasani-Dibra transversal zone. In the zone of Elbasani, hot mineral water (thermal waters) spot out from natural springs which have been known since the 19th century. We estimate the 3D seismic velocity structure in the Elbasani zone to understand the factors controlling the genesis of such earthquakes. A narrow low-velocity zone is imaged within the transversal fault zone over a length of ∼50 km, which partly penetrates into the mantle. The low-velocity zone correlates in space with the NE-SW trending earthquake cluster. A reactivation of thermal water fracture zone is probably related to the low-velocity anomaly.Where geological conditions are favourable, rainwater seeps through the surface and becames trapped in vast underground reservoirs so deep below the Earth”s surface that it becomes heated to high temperatures by the LVFZ. The typology of earthquakes in Elbasan-Dibra comprises all three main well-known types of earthquakes: the earthquakes with main-shock followed by aftershocks, the earthquakes with foreshocks, the compound earthquakes, and the swarms. Seismic hazard for series of earthquakes in this urban area is very high and direct connection with the geology and hydrogeology of the location.