An instrumental earthquake catalogue for the offshore Maltese Islands region, 1995-2014

Abstract

We present the first instrumental earthquake catalogue for Malta using 20 years of broadband seismic data recording. For about two decades Malta had only one station (WDD) which formed part of regional networks. Its location in the eastern part of the Sicily Channel puts the station at the periphery of these networks with the result that weak, off-shore earthquakes that occur between Malta and Libya, are in many cases recorded on WDD only and are undetected or unlisted by the regional networks. We adopt the single-station earthquake location method to process the continuously recorded seismic data of station WDD from 1995 to 2014. We combine our earthquake list with the bulletins of INGV and IRIS to catalogue 550 earthquakes. We statistically quantify the uncertainties of the earthquake epicentres and establish that many earthquake locations differ from INGV/IRIS locations by < 20 km at local epicentral distances from WDD and that earthquake magnitudes determined from single station are overestimated by 0.2. We find that the Malta and Linosa grabens are seismically active, and a high concentration of seismic activity is located 80–120 km SSE of Malta at around 35° N latitude. Closer to land, clusters of epicentres are also located, within 40 km to the east and south of Malta. This new earthquake catalogue shows that the regional seismicity is higher than previously observed and that a number of submarine structures in the area are active as part of the ongoing extension in the Sicily Channel.