A single-station automated earthquake location system at Wied Dalam Station, Malta

Abstract

The seismicity of the Sicily Channel, bordered by the Sicilian, Tunisian, and Libyan coastlines, is mainly controlled by active faults of the Sicily Channel rift zone (SCRZ). This region is characterized by a moderate level of earthquake activity with magnitudes generally below 5.0. However, most seismicity, especially south of the Maltese islands, has, to date, either gone unreported or been poorly located owing to difficulties in instrumental coverage. Since many earthquakes are recorded only on a single station on Malta (broadband station WDD), it was deemed necessary to develop a routine procedure for detecting and locating earthquakes using three-component polarization analysis. Such a system, nicknamed LESSLA (Local Earthquake Single-Station Location Analyser) has been successfully implemented since 2005. It uses an automated method of recognizing local/regional events based on a weighting scheme applied to triggers in different sampling streams. LESSLA has allowed a lower detection threshold for earthquakes in the Sicily Channel, and as a result provided new insights into the pattern of seismicity on the rift zone. LESSLA has also had a good success rate at rapidly and accurately reporting larger events as far as the Greek subduction zone. The description, performance, and limitations of the system are here discussed.