Robust analysis for the characterization of the seismo-electromagnetic signals observed in southern Italy

Seismo‐electromagnetic signals (SES) are anomalous electromagnetic signals generated as a response to the propagation of a mechanical perturbation within the subsoil. Fluid presence plays a key role in determining SES generation and characteristics, therefore SES study could be useful for subsoil characterization. In a more general framework, it can give insight about the role of fluids in the earthquake generation and seismic wave propagation. A systematic study on SES and the related data analysis techniques is fundamental to define the characteristics of these signals which are superimposed to the natural electromagnetic field induced by the external variable magnetic field. To this aim, the Pollino seismic swarm was a great opportunity because continuous MagnetoTelluric (MT) data were recorded in a period in which numerous seismic events of various magnitudes occurred. During the observational period, SES have also been recorded in correspondence to earthquakes far from the MT stations over 800km. In this paper, we present a procedure aimed to improve the SES detectability and gather as much information as possible on these signals. The procedure is especially tuned for the analysis of MT time series and is based on the application of the Continuous Wavelet Transform (CWT) and frequency filters. As will be shown, the operational scheme allows minimizing the background variability of the MT signal facilitating SES detection and the characterization in terms of amplitude and duration

Integrated methodologies for assessing the provenance of building materials from the Roman pier of San Cataldo (Adriatic coast, southern Italy)

A multidisciplinary and multiparametric approach is proposed with the purpose of establishing the original quarries of the building materials used in a monumental pier of the Roman age located in San Cataldo (Lecce, Apulia Region), the main harbour of the Roman town of Lupiae. The pier, dug up after a three years long archaeological campaign, shows a massive structure and consists of two outer curtains made up by large squared limestone blocks and a core in opus caementicium. In the manufacture of the outer curtains, three different calcarenite varieties have been recognized, all belonging to the Pietra Leccese Fm., a Miocene calcarenite, greenish-straw or yellow-whitish in colour, which crops out in a broad geographical area of the Salento Peninsula. About 50% of the rock blocks, used mainly in the upper part of the structure, generally presents a greenish colour and is very rich in glauconite and phosphatic nodules. These are limestone blocks belonging to the “Piromafo” variety, a well-known rock type of Pietra Leccese which lies in the higher stratgraphic level of the formation. Micropalaeontological content allows to classify the material as a biomicrite rich in planktonic Foraminifera of the Miocene (Tortonian-Messinian). In addition, the biostratigraphical characteristics are very similar to some outcrops at Acaya-Strudà, a locality some 10 km south of the ancient harbour. Comparative analyses, biostratigraphical and physical (density and micropore structure) in types, have been performed, supporting a clear identification of the geological origin of the limestone blocks. In respect of the hydraulic concrete used in the opus caementicium, different lithic materials have been used and mixed with a strong mortar. Macroscopic field observations clearly define that the limestone clasts, very heterogeneous in size, derive from the Uggiano la Chiesa Fm. (Pliocene) that widely crops out locally at San Cataldo; the granular fractions of the mortar probably derive from beaches and/or sandy dunes, available in the surrounding area, as well

SWAN: A surface-towed modular controlled-source electromagnetic system for mapping submarine groundwater discharge and offshore groundwater resources

Offshore freshened groundwater (OFG) and submarine groundwater discharge (SGD) are important components of coastal hydrologic systems. A lack of understanding of offshore groundwater systems and their interactions with onshore systems along the majority of global coastlines still exists due to a general paucity of field data. Recently, controlled-source electromagnetic (CSEM) techniques have emerged as a promising noninvasive method for identifying and characterizing OFG and SGD. Unfortunately, only a few systems are available in academic and research institutions worldwide, and applications are limited to specific regions. These systems are often limited by relatively high deployment costs, slow data acquisition rates, logistical complexity, and lack of modification options. A relatively inexpensive and user-friendly CSEM system is needed to overcome these limitations. We present the initial theoretical and practical developments of SWAN — a low-cost, modular, surface-towed hybrid time-frequency domain CSEM system capable of detecting OFG and SGD to water depths of 100 m. A field test of the system was carried out in the central Adriatic Sea at water depths between several tens to approximately 160 m to illustrate its capabilities. Through its ability to facilitate continuous measurements in both the time and frequency domain, the system has demonstrated its effectiveness in acquiring high-quality data while operating at towing speeds ranging from 2.5 to 3 kn. The resulting data coverage enables the system to detect variations in subsurface resistivity to depths of approximately 150–200 m below seafloor. With its modular, user-friendly design, SWAN provides an accessible, cost-efficient means to investigate the hydrogeology of shallow offshore environments