Showing papers by "Cesare Comina published in 2022"

Geotechnical Screening of Linear Earth Structures: Electric and Seismic Streamer Data for Hydraulic Conductivity Assessment of the Arignano Earth Dam, Italy

Abstract: River embankments and small earth dams are linear retaining structures commonly used to protect densely populated areas from flood phenomena and to provide water reservoirs for human or agricultural use. Their continuity and uniformity are fundamental to their structural efficiency. Due to their significant length and the localized nature of potential weakness points, their characterization cannot rely only on local geotechnical investigations: it requires the application of efficient and affordable investigation methods. The need for new screening tools is becoming increasingly important worldwide because most river embankments and small earth dams are reaching their design life limit due to aging. This study used a new electric streamer and a seismic streamer for the combined measurement of resistivity and shear wave velocity to investigate the Arignano earth dam (Piedmont Region, northwestern Italy), a historical reservoir used for agricultural purposes. A procedure is also proposed to assess hydraulic conductivity from the measured geophysical parameters. The results of this assessment were compared with available geotechnical investigations and also used for calibrating the proposed procedure. Results are in good agreement when compared with local geotechnical investigations. The proposed procedure can therefore provide engineers and local authorities with information to plan maintenance or urgent measures for reducing flood risk.

A multidisciplinary approach to detect the seismogenic source of the Tortona 1828 earthquake (Piedmont, Northwest Italy)

Abstract: In areas with flat morphologies formed at the expense of soft rocks, detecting capable faults requires a field- based multidisciplinary approach to help bridge the knowledge gap. In this paper, we present the results of an investigation in the Tortona area (Northwest Italy), where, in 1828, an earthquake caused several casualties and significant diffused damages. Considering the relative “agedness” of this event and the absence of particularly intense seismic activity during recent years, the seismic risk of the epicentral area has not been investigated in detail. To obtain an evaluation of it, twenty-two archives and libraries have been consulted, searching for published and unpublished documentation containing the description of the coseismic effects. The obtained information has been compared with the most updated catalogues. An intensity in the Mercalli intensity scale has been assigned to each new macroseismic data point. Instrumental seismicity has been evaluated to get an estimate of the current released seismic energy. A field survey, coupled with aerial photo interpretation and Digital Elevation Model analysis, has been carried out to verify the presence of tectonic, as well as lithological, influence on the drainage pattern distribution. In this way, geomorphic evidence related to active tectonics has been investigated in the study area. Sharp deviations of the hydrographic network have been detected in the sectors crossing the Staffora and Curone Rivers. Geophysical surveys were used to evaluate the thickness of Quaternary successions and whether they document the presence of geological elements ascribable to capable faults. The investigations suggest the possible presence of a high angle, E-W striking fault affecting Late Pleistocene alluvial deposits.