The Malta Seismic Network : from earthquake monitoring to seismic imaging of groundwater

Abstract

Following the setting up of the Malta Seismic Network, new opportunities for research arise which go beyond the conventional monitoring of local and regional earthquakes. The new data is used to carry out site response studies as well as high-resolution subsurface studies such as velocity profiles and groundwater imaging of the aquifers below. These studies have significant importance for Malta, particularly because it is a small island country 15 km wide by 30 km long in the centre of the Mediterranean Sea (about 100 km south of Sicily, Italy). The network operated by the Seismic Monitoring and Research Group at the University of Malta is being exploited to maximize its full potential aiding the local Department of Civil Protection with earthquake monitoring and tsunami modelling and now the Energy and Water Agency with groundwater monitoring. We present the recent developments of the seismic network, examples of local earthquake recordings, earthquake catalogue and site response studies. In addition, we present SIGMA (Seismic Imaging of Groundwater for Maltese Aquifers), a new project aimed at imaging the spatial and temporal characteristics of aquifers across Malta – a first to cover a whole country that is completely surrounded by sea. The data set is derived from a combination of 13 stations, including those of the Malta Seismic Network and other temporary instruments spanning across the whole archipelago. We use auto/cross-correlation of noise recorded on the stations to extract information about the subsurface and track temporal and spatial changes in water content at different scales. These changes are compared to in situ borehole readings and meteorological parameters.