Progress report on the ongoing activity for constructing a catalogue of geological/geotechnical information at accelerometric stations

The main goals within Task2 are: • the development of the new standard format for station monograph; • collection, organization and synthesis of geological, geomorphological, geotechnical and geophysical data; • evaluation of the reliability of the existing data; • compilation of station monographs; • a site classification. All the research units are involved in the collection and elaboration of data relevant to the compilation of the monographs. RU2 (INGV-RM1) and RU6 (UniRM1-DISG) have directly contributed in the development of the structure and content of the new monograph, and in the release of the first proposal of site classification. Additional contributions from other RUs concern the assessment of the reliability of the existing shear wave velocity data (RU4 - PoliTO), the preparation of the geomechanical section of the new monograph (RU7 - UniSI-UniRM1-DST) and for web support to data collection and online monograph compilation (RU1 (INGV-MI)

The new ITACA monograph: main features and data compiling

The activities carried out within Task 2 aim to collect, organize and synthesize geological, geomorphological, geotechnical and geophysical data for the location site of the Accelerometric National Network (RAN) stations in Italy, managed by the Department of Civil Protection. Knowledge of geological and geomorphological context, and the mechanical and dynamic characteristics of the stations subsoil is an important factor for studies on the attenuation laws and the choice of accelerograms related to the subsoil category provided by seismic code. Having to produce on a large number of sites (over 600), this knowledge have to be rationalized and homogenized so as to arrive at a common and comparable level of information. With this goal has been organized and implemented the activities within Task 2

Summary of recent gaseous reactor fluid mechanics experiments

Summaries of recent gaseous reactor fluid mechanics experiment

Seismic Response Analysis of Historical Towns Rising on Rock Slabs Overlying a Clayey Substratum

Two case histories are presented which refer to the historical towns of Orvieto and Bisaccia, both located on top of rock buttes overlying a more deformable clayey substratum. The comparison of the two case histories indicates that apparently similar geological conditions do not lead to the same type of seismic response. In fact, the specific physical and dynamic properties of the substratum and the overlying slab can determine different seismic behaviour at the hill top and at the rock-clay interface. In particular, at Bisaccia a deamplification of the seismic motion at the hill top was predicted, as well as the development of excess pore pressures in the clay deposit underneath the conglomerate. On the other hand, at Orvieto significant amplification of surface motion is expected, due to the impedance contrast between the different pyroclastic materials of the rock slab and to the topography effect at the slab edge as well

Seismic Response Analysis of Historical Towns Rising on Rock Slabs Overlying a Clayey Substratum

Two case histories are presented which refer to the historical towns of Orvieto and Bisaccia, both located on top of rock buttes overlying a more deformable clayey substratum. The comparison of the two case histories indicates that apparently similar geological conditions do not lead to the same type of seismic response. In fact, the specific physical and dynamic properties of the substratum and the overlying slab can determine different seismic behaviour at the hill top and at the rock-clay interface. In particular, at Bisaccia a deamplification of the seismic motion at the hill top was predicted, as well as the development of excess pore pressures in the clay deposit underneath the conglomerate. On the other hand, at Orvieto significant amplification of surface motion is expected, due to the impedance contrast between the different pyroclastic materials of the rock slab and to the topography effect at the slab edge as well

Evaluation of site effects by means of 3D numerical modeling of the Palatine Hill, Roman Forum, and Coliseum archaeological area

In this study we perform 3D nonlinear analyses of seismic site response of the Central Archaeological Area of Rome, which includes the Palatine Hill, Roman Forum, Circus Maximus, and Coliseum. The geological bedrock of the study area is constituted by a Pliocene marine sandy-clayey unit (MonteVaticano Formation, MVA). At top of this unit a continental Quaternary succession is superimposed. Previous studies available for this area (Pagliaroli et al. 2014a; Mancini et al. 2014; Moscatelli et al. 2014) enabled to define a detailed three-dimensional reconstruction of the subsoil conditions, characterized by complex surficial and buried morphology, lateral heterogeneities and dynamic properties of involved material, natural as well as anthropogenic. The area of Rome is affected by earthquakes from different seismogenic districts: i) the central Apennine mountain chain (D = 90–130km and M = 6.7–7.0); ii) the Colli Albani volcanic district (D = 20km and M=5.5); iii) Rome area itself, which is characterized by rare, shallow, low-magnitude events (M < 5). Both natural and artificial signals have been considered to define the input motion for the numerical modeling of the site response of the whole archeological area. This was accomplished by means of the finite differences code FLAC3D. To evaluate the seismic hazard and, consequently, to assess possible priorities for seismic retrofitting of the monuments, contour maps of Housner intensity amplification ratio FH (defined as the ratio between Housner intensity at the top of the model and the corresponding input at the bedrock outcrop), are carried out. To cover the entire range of natural periods pertaining to the monuments in the examined area, FH was evaluated over three ranges of period: 0.1–0.5s, 0.5–1.0s, and 1.0–2.0s. Numerical results shown that: 1) within the range of periods 0.1–0.5s, high values of FH = 2.2–2.6 occur both in correspondence of narrow valleys filled with soft alluvial deposits and at top of Palatine Hill; 2) within the range of periods 0.5–1.0s, high values of FH occur in correspondence of the deepest valleys; 3) within the range of periods 1.0–2.0s, low values of FH occur except in correspondence of the deepest valleys.Results show a good agreement with the previous 2D numerical modeling and with the microzonation maps (Pagliaroli et al 2014a, b), even if interesting differences show up highlighting the usefulness of 3D modeling in such complex settings. Such results are significantly relevant for the monumental and archaeological heritage of this area, as it is highly vulnerable due to its old age and state of conservation

The safety assessment of Campotosto Lake dams following 2016-2017 seismic sequence in Central Italy. Focus on Poggio Cancelli embankment dam

The Campotosto Lake is one of the biggest reservoirs of Europe, with a storage capacity exceeding 200 million of m3. The natural original lake was confined with three large dams owned by Enel. In the recent past, the lake and the dams have been subjected to a series of seismic events known as the seismic sequence of L'Aquila in 2009 and the seismic sequence of Central Italy in 2016-17. Following the last one, Enel promptly decided to temporarily lower the water level to carry out surveys, measurements and automatic monitoring activities. Based on available data, in order to verify, ensure and asseverate the safety conditions of the dams and the lake’s slopes, a series of multi-disciplinary studies and in-depth analysis were specifically conducted. Detailed studies were developed for the Poggio Cancelli embankment dam: geotechnical surveys, geophysical in situ tests and “advanced” laboratory tests in order to define at best the foundation soil characteristics, thus reasonably excluding the liquefaction risk applying sophisticated methods of analysis. Moreover, InSAR analysis allowed to retrieve the displacement history of the sites and confirmed the topographic measurements taken before and after the earthquakes. Displacement data, together with the real accelerograms recorded at the dam toe were used for a back analysis of the settlements by means of a FEM model of the dam. With this validated model, it was possible to simulate the seismic response of the embankment in the catastrophic scenario represented by the worst expected earthquake at the site. However, recent and important research contributed to establish the position and associated potential magnitude of the Campotosto fault. They indicate that the seismic scenario adopted by our analysis is precautionary, therefore our results are conservative. Seismic assessments on the other dams and InSAR analysis of the slopes surrounding the reservoir were also carried out. All these studies were concluded in 2020 showing good results and satisfactory safety factors, allowing Enel to set up again Campotosto reservoir to normal water levels

Revised seismic classification of the ITACA stations, according to the EC8 and the Italian norms site classes

The activities carried out within Task 2 aim to collect, organize and synthesize geological, geomorphological, geotechnical and geophysical data for the location site of the Accelerometric National Network (RAN) stations in Italy, managed by the Department of Civil Protection, to improve the knowledge about the subsoil (see Delverable D05) and to permit a subsoil and topographic site classification based on EC8 categories. At the end of the project the subsoil of 695 stations have been classified using an hybrid approch, based on surface geology, spectral classification and Vs profils from different recording tecniques (DH, CH, MASW, ESAC). These activities have been useful to link the ITACA database with the software REXEL to select natural accelerograms, compatible with Norme Tecniche per le Costruzioni (NTC2008) and EUROCODE 8 (EC8) spectra, which may also reflect characteristics of the source in terms of magnitude and epicentral distance. For 688 station sites have been provided also a topographic classification using a GIS based semiautomatic method with “by-hand” corrections using topographic maps and/or Google Earth software. A Microsoft Excel Database which also allows to track all changes that have been made since the beginning of the project related to the site classification has been developed

Seismological and geotechnical aspects of the Mw=6.3 l’Aquila earthquake in central Italy on 6 April 2009

The L’Aquila earthquake occurred on April 6 2009 at 03:32:39 local time. The earthquake (Mw=6.3) was located in the central Italy region of Abruzzo. Much of the damage occurred in the capital city of L’Aquila, a city of approximate population 73000, although many small villages in the surrounding region of the middle Aterno river valley were also significantly damaged. In the weeks following the earthquake, the Geo-Engineering Extreme Events Reconnaissance (GEER) international team, comprised of members from different European countries and the U.S., was assembled to provide post-earthquake field reconnaissance. The GEER team focused on the geological, seismological, and geotechnical engineering aspects of the event. We describe the principal seismological findings related to this earthquake including moment tensors of the main shock and two triggered events, the aftershock pattern and its variation with time, tectonic deformations associated with the main shock, surface fault rupture, and the inferred fault rupture plane. We describe damage patterns on a village-to-village scale and on a more local scale within the city of L’Aquila. In many cases the damage patterns imply site effects, as neighbouring villages on rock and soil had significantly different damage intensities (damage more pronounced on softer sediments). The April 6 mainshock was the best-recorded event to date in Italy. We present metadata related to the recording sites and then present preliminary comparisons of the data to GMPEs. Those comparisons support the notion of faster distance attenuation in Italy relative to the average for active regions as reflected in NGA GMPEs. Several incidents of ground failure are then discussed, including a number of rockfalls and minor landslides. Perhaps the most significant incidents of ground failure occurred at Lake Sinizzo, for which we describe a number of slumps and spreads around the lake perimeter. This is documented using field observations as well as LIDAR and bathymetric data

Definition of the standard format to prepare descriptive monographs of ITACA stations

In the previous S6 Project (2004-2007 DPC-INGV Framework Program) a monograph was carried out, that was drawn up for many stations, that were part of the former ENEL accelerometric network. In these monographs all the ENEL documentation about geological information as well as geognostic and geophysical data was included. Knowledge of geological and geomorphological context, and the mechanical and dynamic characteristics of the stations subsoil is fundamental for studies on the attenuation laws and the selection of accelerograms to be used as a seismic input for dynamic analyses for which a classification of the stations subsoil according to the EC8 and national code provisions is necessary. Considering the huge number of sites (over 600), this knowledge have to be rationalized and homogenized so as to arrive at a common and comparable level of information. The station monograph carried out within the past S6 INGV Project had tried to fill the gap in the knowledge of the recording station characteristics, with the advantage of providing a first screening on the quantity and quality of available data; however the collected data included in the monograph turned out to be uneven and incomplete since a robust standard for the collection, homogenization, representation and synthesis of data was not provided. Moreover, expert judgment for assessing quality of data, especially those derived from geotechnical and geophysical tests, was not taken into consideration. This problem has been addressed by Task 2, which has produced a new standard monograph for the ITACA stations. The new release of the station monograph is the first product of the 5 S4 Project (deliverable D3) and can be downloaded from the project website (http://esse4.mi.ingv.it). The new ITACA monograph provides a minimum level of information, homogeneous for all station sites, including multi-disciplinary data to satisfy the needs of different users and duly considers information previously not included. In detail, the new ITACA monograph consists in the following 12 cognitive modules, and various sub-modules