Shallow electrical and seismic imaging of the Pineto Mud Volcano (Central Italy)

Shallow underground electrical and seismic imaging was undertaken at the Pineto (Central Italy) Mud Volcano site using 2D-3D electrical resistivity tomography (ERT) and 2D reflection seismic surveys. This mud volcano or mud lump (known by the local population as “Cenerone Mud Volcano”) appears as a dome of about 15x10 m in size. The height is approximately 2 m with a crater 2.5 m of diameter where emission of fluids and solids (cold brine, mud, gas) occurs. Upper Pliocene-Lower Pleistocene foredeep pelitic deposits (clays with silty-sandy levels) overlain by clayey-silty deposits outcrop in the area. Below the Middle Pliocene deposits, a NNW-SSE anticline which runs approximately 2 kilometers to the WSW of the site represents the main element of the compressional tecnonic setting. Ditchs and streams in the area run along fault systems that are oriented NW-SE and NE-SW. These could be related to the upward migration of deep mud fluids. 2D-ERT results were used to determine the geometry of the high conductivity body related to the uprising of mud fluids and detecting changes in deposits. Detailed geometry reconstruction of the shallow upward migration of mud fluids was obtained by using 3D-ERT. A shear wave reflection seismic survey was undertaken to determine stratigraphic limits and to assess the occurrence of fractured zones along which mud fluids could migrate towards the surface. The survey results revealed that the uprising of deep fluids doesn’t occur exactly below the mud volcano at present. Instead, a high conductivity body occurs at approximately 60 m to the ENE, within a fractured zone in the undercompacted clays. The probable occurrence of a high permeability layer approximately between 20 m and 30 m below ground level, confined by clay layers, gives rise to an overpressured mud reservoir. This is the source of mud fluids which flow to the surface through a mud conduit that appears nearly horizontal at depth and then inclined towards the surface up to the mud volcano crater

Reliability Assessment of Digital Terrain Models drawn from Digital Photogrammetry

The modern techniques of Digital Photogrammetry are used to reconstruct Digital Terrain Models (DTMs) from photosets taken by commercial digital cameras. The algorithms are based on the Multiview Stereo Vision (MVS) which draw a 3D model in the space through the internal setting of the digital photosets. In this study, two open source codes, VisualSfM and CMP-MVS are used to combine the photosets to build the DTM of the Civitaluparella (CH) quarry wall. This latter is compared with the reference DTM reconstructed by a Laser Scanner device (in this application the Long-Range Topcon GLS-1500 laser scanner has been used). The comparison evidences spatial errors about ±0.1m along y and z directions and ±0.2m along x direction for the DTM drawn by the Digital Photogrammetry for the vertical quarry wall. Hence, these outcomes confirm the reliability of the Digital Photogrammetry codes as fast and cheap tool for drawing accurate Digital Terrain Models. These DTMs can be used for generating Digital Elevation Models (DEMs) for engineering geological applications such as slope stability analyse

Application of 1D-2D electrical resistivity surveys to the identification and investigation of shallow paleochannels in the Chamelecòn Valley (Honduras)

Il lavoro confronta i risultati ottenuti dall’utilizzo di due differenti metodi di prospezione elettrica, nell’ambito di uno studio finalizzato alla ricerca e caratterizzazione di paleoalvei presenti in due siti opportunamente selezionati lungo la valle del Rio Chamelecòn (Honduras). L’applicazione di sondaggi elettrici verticali (1D) ha permesso di determinare la presenza di paleoalvei; la caratterizzazione geometrica e litologica di questi è stata invece ottenuta mediante applicazione di indagini di tomografia elettrica 2D (ERT)

Indagini geotecniche e geofisiche per la caratterizzazione del sito di Castelnuovo Garfagnana (Lucca)

Il presente articolo riporta i risultati relativi alle indagini geofisiche e geotecniche condotte per la definizione del modello atto a descrivere la risposta sismica locale nel centro di Castelnuovo Garfagnana. Tali indagini si inquadrano nel progetto VEL, intrapreso dalla Regione Toscana per lo studio degli effetti sismici locali nei territori della Garfagnana e della Lunigiana. Il comune di Castelnuovo (6500 abitanti distribuiti su un territorio di ca. 28 km2) costituisce in tale ambito un caso pilota per la definizione delle metodologie di indagine e di modellazione. Il piano di indagine definito per la caratterizzazione dei depositi ha preso spunto dalle informazioni riguardanti la geologia locale ed è stato sviluppato con l'uso di tecniche geofisiche in sito e l'esecuzione di prove geotecniche di laboratorio su campioni indisturbati prelevati dai siti in esame. In particolare vengono riportati alcuni aspetti metodologici riguardanti le prove eseguite ed i risultati ottenuti, ponendo l'attenzione principalmente sui seguenti aspetti: - Interrelazione tra indagini geofisiche e geotecniche - Confronto tra diverse tecniche geofisiche sismiche (Down-Hole, SASW e Sismica a Rifrazione per onde SH) - Confronto tra differenti prove in laboratorio (Triassiali Monotoniche e Cicliche, Colonna Risonante, Taglio Torsionale Ciclico) - Definizione dei parametri di modello per lo studio dell'amplificazione locale sulla base dei risultati sperimentali Gli obiettivi principali dell'articolo sono: i) definire potenzialità e limiti delle differenti metodologie di prova in sito e in laboratorio ii) riportare informazioni dettagliate riguardanti un esempio ben documentato di studio degli effetti sismici local

Indagini geotecniche e geofisiche per la caratterizzazione del sito di Castelnuovo Garfagnana (Lucca)

Il presente articolo riporta i risultati relativi alle indagini geofisiche e geotecniche condotte per la definizione del modello atto a descrivere la risposta sismica locale nel centro di Castelnuovo Garfagnana. Tali indagini si inquadrano nel progetto VEL, intrapreso dalla Regione Toscana per lo studio degli effetti sismici locali nei territori della Garfagnana e della Lunigiana. Il comune di Castelnuovo (6500 abitanti distribuiti su un territorio di ca. 28 km2) costituisce in tale ambito un caso pilota per la definizione delle metodologie di indagine e di modellazione. Il piano di indagine definito per la caratterizzazione dei depositi ha preso spunto dalle informazioni riguardanti la geologia locale ed è stato sviluppato con l'uso di tecniche geofisiche in sito e l'esecuzione di prove geotecniche di laboratorio su campioni indisturbati prelevati dai siti in esame. In particolare vengono riportati alcuni aspetti metodologici riguardanti le prove eseguite ed i risultati ottenuti, ponendo l'attenzione principalmente sui seguenti aspetti: - Interrelazione tra indagini geofisiche e geotecniche - Confronto tra diverse tecniche geofisiche sismiche (Down-Hole, SASW e Sismica a Rifrazione per onde SH) - Confronto tra differenti prove in laboratorio (Triassiali Monotoniche e Cicliche, Colonna Risonante, Taglio Torsionale Ciclico) - Definizione dei parametri di modello per lo studio dell'amplificazione locale sulla base dei risultati sperimentali Gli obiettivi principali dell'articolo sono: i) definire potenzialità e limiti delle differenti metodologie di prova in sito e in laboratorio ii) riportare informazioni dettagliate riguardanti un esempio ben documentato di studio degli effetti sismici locali

Site resonance frequency assessment through dynamic load testing (DLT): early results of a test carried out in the experimental site of Fivizzano (MS, Italy)

The assessment of the local seismic response is one of the fundamental phases when it comes to defining the levels of seismic hazard at a detailed scale. These are typically known as seismic zonation studies. The estimation of the site specific resonance frequency is a parameter of relevant interest within such studies as it is associated with the maximum seismic amplification which has to be related to the frequency of resonance of buildings. The ambient noise based methods and other experimental methods for measuring this parameter are not always applicable because they are strongly influenced by contrasts of impedence and by lateral subsurface heterogeneities. Furthermore, they sometimes present limits that are not always clearly known. On the other hand, the classic analytical approach that makes use of integrated and multidisciplinary investigation methods, which estimate the local amplification parameters, mainly in terms of amplification factors and response spectrums, currently presents uncertainties and limitations. These are essentially associated with the difficulty of modelling the mechanisms of propagation of the seismic waves within a 3D system. The authors of this paper propose the experimental measurement of the site resonance frequency by means of Dynamic Load Testing (DLT). This is done by presenting the operative procedures, the data processing and the results obtained from a test undertaken at the experimental site of Fivizzano (Massa-Carrara, Italy) where a detailed study of the local seismic response was also undertaken. The test involved the delivery of sinusoidal forces with maximum amplitude of 20 kN and a range of frequencies between 0 and 15 Hz by means of an electro-mechanical generator. Simultaneous seismic monitoring was undertaken through a multichannel acquisition system. Velocimeters were placed on the ground and in a nearby strategic building. The measured frequency of resonance was compared to the predicted value obtained from empirical-analytical solutions and application of horizontal to vertical spectral ratios (HVSR) method and to the value measured by a seismic station equiped with two coupled accelerometers, one at the surface and one at depth; these sensors allowed an accurate analysis of the effects of the drift deposits overlying the bedrock, that is the transfer function of the stratigraphic column at the site

Geological and geotechnical investigations for the seismic response analysis at Castelnuovo Garfagnana in Central Italy

The Tuscany regional government has started a comprehensive project for the evaluation of site effects in about 60 municipalities, located in the territories of Garfagnana and Lunigiana that are under its authority. For this purpose a multidisciplinary task force has been working in order to assess the elastic response spectra taking into account both topographic and stratigraphic amplifications. The main objective is to provide a tool for land use planning, design of new structures and retrofitting of the existing ones. This kind of activity is nowdays completed for Castelnuovo Garfagnana, that is a town of about 6500 inhabitants with a territory of about 28 square Km. The paper mainly focuses on the geological, geophysical and geotechnical investigations concerning the town of Castelnuovo Garfagnana. The results are summarised with special attention to the following aspects: interplay between geological, geophysical and geotechnical investigations; comparison among different geophysical testing methods (Down-Hole, SASW, Seismic refraction); comparison among different laboratory tests (Monotonic and cyclic triaxial tests, resonant column tests, cyclic torsional shear tests); treatment of the experimental results in order to define a model for the subsequent seismic analysis; creation of a database. The main objectives are i) to point out capabilities and limitations of different in situ and laboratory testing methods and ii) to provide enough information on a well-documented case history. The results of seismic analysis at Castelnuovo Garfagnana are reported in a companion paper

Italian accelerometric archive: geological, geophysical and geotechnical investigations at strong – motion stations

Geological, geophysical and geotechnical investigations, for the characterization of the strong-motion recording sitesmanaged by the ItalianCivil Protection, have been carried out in the framework of the project “Italian strong-motion database in the period 1972–2004”. The project aimed at creating an updated database of strong-motion data acquired in Italy by different institutions in the time span 1972–2004, and at improving the quality of disseminated data. This article illustrates the state of the recording site characterization before the beginning of the project, explains the criteria adopted to select the sites where geophysical/ geotechnical investigation have been performed and describes the results of the promoted field surveys