An augmented seismic network to study off-shore seismicity around the Maltese Islands : the FASTMIT experiment

Appropriate planning and deployment of a seismic network is a prerequisite to efficiently monitor seismic activity, determine the seismic source, and eventually contribute to the seismotectonic interpretation and seismic hazard assessment. The evaluation and effectiveness of a local network on the Maltese islands, recently extended by a further six seismic stations for one year, is presented. We investigate the new temporary network's data and site selection quality, utilizing spectral patterns in the seismic data and also evaluate the network's event location performance by relocating a number of recorded events. The results will be signifi cant for the future installation of permanent seismic stations on the Maltese islands.peer-reviewe

Characteristics of the recent seismic activity on a near-shore fault south of Malta, Central Mediterranean

The tectonic setting of the Maltese islands is mainly influenced by two dominant rift systems belonging to different ages and having different trends. The first and older rift created the horst and graben structure in northern Malta. The second rift generation, in the south, including the Maghlaq Fault, is associated with the Pantelleria Rift. The Maghlaq Fault is a spectacular NW - SE trending and left-stepping normal fault running along the southern coastline of the Maltese islands, cutting the Oligo-Miocene pre to syn-rift carbonates. Its surface expression is traceable along 4 km of the coastline, where vertical displacements of the island's Tertiary stratigraphic sequence are clearly visible and exceed 210m. These displacements have given rise to sheer, slickensided fault scarps, as well as isolating the small island of Filfla 4km offshore the southern coast. Identification and assessment of the seismic activity related with Maghlaq fault, for the recent years, is performed, re-evaluating and redetermining the hypocentral locations and the source parameters of both recent and older events. The earthquakes that have affected the Maltese islands in the historical past, have occurred mainly at the Sicily Channel, at eastern Sicily, even as far away as the Hellenic arc. Some of these earthquakes also have caused considerable damage to buildings. The Maghlaq fault is believed to be one of the master faults of the Sicily Channel Rift, being parallel to the Malta graben, which passes around 20km south of Malta and shows continuous seismic activity. Despite the relationship of this fault with the graben system, no seismic activity on the Maghlaq fault had been documented previous to 2015. On the July 30nth 2015, an earthquake was widely felt in the southern half of Malta and was approximately located just offshore the southern coast. Since then, a swarm of seismic events lasting several days, as well as other isolated events have occurred, indicating the fault to be seismically active. Investigation of the nature of the seismic events and other previous activity that may have been misclassified due to poor location capability, is performed. Such results are of utmost importance in order to reveal the implication of this newly-discovered activity on the seismic hazard to the Maltese islands and also to improve understanding of the local geodynamics, highlighting the mechanisms that contribute to both the crustal deformation and the tectonics of the upper crust. The investigation is carried out using the stations of the recently extended Malta Seismic Network and regional stations. The results are evaluated in the context of the role of the Maghlaq fault in the extensional tectonics associated with the Sicily Channel Rift and the African continental margin.peer-reviewe

An updated seismicity map of the Sicily Channel through improved seismic networks on the Maltese islands and Central Mediterranean

The Sicily Channel, bordered by the Sicilian and Tunisian coastlines, the Sicily-Malta escarpment to the east, and the Maghrebian thrust front to the west, is a tectonically interesting region, encompassing a NE-directed extensional process superimposed on the NW-directed thrust of Africa onto Europe. The extension is bathymetrically represented in the form of deep NW-SE oriented grabens in the sea floor, reaching a depth of over 1000 m. The nature of the rifting process is still controversial. The grabens have been investigated from the geophysical and geological aspects, but poorly studied in terms of active seismicity, which is usually referred to as sparse or insignificant in the scientific literature. [excerpt]peer-reviewe

Coseismic deformation, field observations and seismic fault of the 17 November 2015M=6.5, Lefkada Island, Greece earthquake

On November 17, 2015 07:10:07 UTC a strong, shallow Mw6.5 earthquake, occurred on the island of Lefkada along a strike-slip fault with right-lateral sense of slip. The event triggered widespread environmental effects at the south and western part of the island while, the intensity and severity of these earthquake-induced deformations is substantially decreased towards the eastern part of the island. Relocation of seismicity and inversion of geophysical (GPS, InSAR) data indicate that the seismic fault runs parallel to the west coast of Lefkada, along the Aegean – Apulia plate boundary. The fault plane strikes N20 ± 5°E and dips to east with an angle of about 70 ± 5°. Coseismic deformation was measured in the order of tens of centimeters of horizontal motion by continuous GPS stations of NOANET (the NOA GPS network) and by InSAR (Sentinel 1 A image pairs). A coseismic uniform-slip model was produced from inversion of InSAR data and permanent GPS stations. The earthquake measured Mw = 6.5 using both the geodetic moment produced by the slip model, as well as the PGD relation of Melgar et al. (2015, GRL). In the field we observed no significant vertical motion of the shoreline or surface expression of faulting, this is consistent with the predictions of the model. The interferograms show a large decorrelation area that extends almost along all the western coast of Lefkada. This area correlates well with the mapped landslides. The 2003–2015 pattern of seismicity in the Ionian Sea region indicates the existence of a 15-km seismic gap offshore NW Cephalonia.Published210-2221T. Deformazione crostale attivaJCR Journa

The national seismic network for the Maltese islands : update 2021

The Maltese islands are a small country 15 km wide by 30 km long located about 100 km south of Sicily, Italy. Since 2015 Malta has set up a national seismic network. The primary aim of this network is to monitor in real-time and to locate more accurately the seismicity close to the islands and the seismicity in the Sicily Channel, offshore between Sicily, Tunisia and Libya. This Channel presents a range of interesting and complex tectonic processes that have developed in response to various regional stress fields mainly as a result of the collision between the African plate with Europe. The Maltese islands are known to have been affected by a number of earthquakes originating in the Channel, with some of these events estimated to be very close to the islands. [excerpt]Funding for stations was provided by Interreg Italia-Malta projects (SIMIT and SIMIT-THARSY, Codes B1-2.19/11 and C1-3.2-57) and by Transport Malta.peer-reviewe

The 25 October 2018 Mw = 6.7 Zakynthos earthquake (Ionian Sea, Greece): A low-angle fault model based on GNSS data, relocated seismicity, small tsunami and implications for the seismic hazard in the west Hellenic Arc

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