Lithological and structural control on the seismicity distribution in Central Italy

2020 ◽  
Author(s):  
Massimiliano R. Barchi ◽  
Lauro Chiaraluce ◽  
Cristiano Collettini
Keyword(s):  
Regional Scale ◽  
Central Italy ◽  
Shear Zones ◽  
Geological Structure ◽  
Rock Properties ◽  
Mountain Range ◽  
Upper Crust ◽  
Seismogenic Layer ◽  
Brittle Ductile Transition ◽  
Seismicity Distribution

<p>In the seismically active region of Central Italy, national (permanent) and local (not-permanent) seismic networks provided very accurate location of the seismicity recorded during the major seismic sequences occurred in the last 25 years (e.g. 1997-1998; 2009; 2016-2017), as well as of the background seismicity registered in the intervening periods.  In the same region, a network of seismic reflection profiles, originally acquired for oil exploration purposes, is also available, effectively imaging the geological structure at depth, to be compared with the seismicity distribution. </p><p>This comparison reveals that, if the position of the brittle/ductile transition exerts a role at regional scale for the occurrence of crustal seismicity, at a more local scale the depth and thickness of the seismogenic layer is mostly controlled by the contrasting rheological properties of the different lithological groups involved in the upper crust. </p><p>The upper crust stratigraphy, including the sedimentary cover and the uppermost part of the basement, consists of alternated strong (rigid, e.g. carbonates and dolostones) end weak (not-rigid, e.g. shales, sandstones, and phyllites) layers. This mechanically complex multilayer is involved in a belt of imbricated thrusts (Late Miocene-Early Pliocene), displaced by subsequent extensional (normal) faults (Late Pliocene-present), responsible for the observed regional seismicity. The top of the basement s.l. (composed of clastic sedimentary and slightly metamorphosed rocks) is involved in major thrusts.  For these different lithological units, combined field and lab studies of fault rock properties have documented localized and potentially unstable deformation occurring in granular mineral phases (carbonates) and distributed and stable slip within phyllosilicate-rich shear zones (shales and phyllites).</p><p>By comparing the geological structure with the seismicity distribution, we observed that:</p><p>-     The seismicity cut-off (i.e. the bottom of the seismogenic layer) is structurally (not thermally) controlled, and grossly corresponds to the top basement; the upper boundary of the seismogenic layer corresponds to the top of carbonates.</p><p>-     Most seismicity occurs within the rigid layers (carbonates and evaporites), and do not penetrate the turbidites and basements rocks.</p><p>-      Close to the axial region of the mountain range, where the larger amount of shortening is observed, the presence thrust sheets from the previous compressional phase, significantly affect the seismicity distribution and propagation.</p><p>-     Major east-dipping extensional detachments, recognized in the seismic profiles, are also marked by distinctive seismicity alignments.</p>

scholarly journals 3D crustal stress state of Germany according to a data-calibrated geomechanical model

Solid Earth ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1777-1799
Author(s):  
Steffen Ahlers ◽  
Andreas Henk ◽  
Tobias Hergert ◽  
Karsten Reiter ◽  
Birgit Müller ◽  
...  
Keyword(s):  
Stress State ◽  
Material Properties ◽  
Regional Scale ◽  
Basic Research ◽  
Horizontal Stress ◽  
Rock Properties ◽  
Upper Crust ◽  
Stress Regime ◽  
Initial Stress State ◽  
Crustal Stress

Abstract. The contemporary stress state in the upper crust is of great interest for geotechnical applications and basic research alike. However, our knowledge of the crustal stress field from the data perspective is limited. For Germany basically two datasets are available: orientations of the maximum horizontal stress (SHmax) and the stress regime as part of the World Stress Map (WSM) database as well as a complementary compilation of stress magnitude data of Germany and adjacent regions. However, these datasets only provide pointwise, incomplete and heterogeneous information of the 3D stress tensor. Here, we present a geomechanical–numerical model that provides a continuous description of the contemporary 3D crustal stress state on a regional scale for Germany. The model covers an area of about 1000×1250 km2 and extends to a depth of 100 km containing seven units, with specific material properties (density and elastic rock properties) and laterally varying thicknesses: a sedimentary unit, four different units of the upper crust, the lower crust and the lithospheric mantle. The model is calibrated by the two datasets to achieve a best-fit regarding the SHmax orientations and the minimum horizontal stress magnitudes (Shmin). The modeled orientations of SHmax are almost entirely within the uncertainties of the WSM data used and the Shmin magnitudes fit to various datasets well. Only the SHmax magnitudes show locally significant deviations, primarily indicating values that are too low in the lower part of the model. The model is open for further refinements regarding model geometry, e.g., additional layers with laterally varying material properties, and incorporation of future stress measurements. In addition, it can provide the initial stress state for local geomechanical models with a higher resolution.

scholarly journals 3D crustal stress state of Western Central Europe according to a data-calibrated geomechanical model – first results

2020 ◽  
Author(s):  
Steffen Ahlers ◽  
Andreas Henk ◽  
Tobias Hergert ◽  
Karsten Reiter ◽  
Birgit Müller ◽  
...  
Keyword(s):  
Stress State ◽  
Central Europe ◽  
Material Properties ◽  
Regional Scale ◽  
Horizontal Stress ◽  
Rock Properties ◽  
Upper Crust ◽  
Stress Regime ◽  
Crustal Stress ◽  
Lithostratigraphic Units

Abstract. The contemporary stress state in the upper crust is of great interest for geotechnical applications and basic research likewise. However, our knowledge of the crustal stress field from the data perspective is limited. For Western Central Europe basically two datasets are available: Orientations of the maximum horizontal stress (SHmax) and the stress regime as part of the World Stress Map (WSM) database (Heidbach et al., 2018) as well as a complementary compilation of stress magnitude data of Germany and adjacent regions (Morawietz et al., 2020). However, these datasets only provide pointwise, incomplete and heterogeneous information of the 3D stress tensor. Here, we present a geomechanical-numerical model that provides a continuous description of the contemporary 3D crustal stress state on a regional scale for Western Central Europe. The model covers an area of about 1000 × 1250 km2 and extends to a depth of 100 km containing seven lithostratigraphic units, with specific material properties (density and elastic rock properties) and laterally varying thicknesses: A sedimentary unit, four different units of the upper crust, the lower crust and the lithospheric mantle. The model is calibrated by the two datasets to achieve a best-fit regarding the SHmax orientations and the minimum horizontal stress magnitudes (Shmin). The modelled orientations of SHmax are almost entirely within the uncertainties of the WSM data used and the Shmin magnitudes fit to various datasets well. Only the SHmax magnitudes show locally significant deviations, primarily indicating too low values in the lower part of the model. The model is open for further refinements regarding model geometry, e.g., additional layers with laterally varying material properties, and incorporation of future stress measurements. In addition, it can provide the initial stress state for local geomechanical models with a higher resolution.

scholarly journals Insights on the seismogenic layer thickness from the upper crust structure of the Umbria-Marche Apennines (central Italy)

Tectonics ◽  
2008 ◽  
Vol 27 (1) ◽  
pp. n/a-n/a ◽  
Author(s):  
F. Mirabella ◽  
M. Barchi ◽  
A. Lupattelli ◽  
E. Stucchi ◽  
M. G. Ciaccio
Keyword(s):  
Layer Thickness ◽  
Central Italy ◽  
Upper Crust ◽  
Crust Structure ◽  
Seismogenic Layer

scholarly journals Comparison between electrical resistivity tomography and tunnel seismic prediction 303 methods for detecting the water zone ahead of the tunnel face: A case study

2020 ◽  
Vol 12 (1) ◽  
pp. 1094-1104
Author(s):  
Nima Dastanboo ◽  
Xiao-Qing Li ◽  
Hamed Gharibdoost
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Geological Structure ◽  
Rock Properties ◽  
Electrical Tomography ◽  
Tunnel Face ◽  
Resistivity Tomography ◽  
Geological Conditions ◽  
Seismic Prediction

AbstractIn deep tunnels with hydro-geological conditions, it is paramount to investigate the geological structure of the region before excavating a tunnel; otherwise, unanticipated accidents may cause serious damage and delay the project. The purpose of this study is to investigate the geological properties ahead of a tunnel face using electrical resistivity tomography (ERT) and tunnel seismic prediction (TSP) methods. During construction of the Nosoud Tunnel located in western Iran, ERT and TSP 303 methods were employed to predict geological conditions ahead of the tunnel face. In this article, the results of applying these methods are discussed. In this case, we have compared the results of the ERT method with those of the TSP 303 method. This work utilizes seismic methods and electrical tomography as two geophysical techniques are able to detect rock properties ahead of a tunnel face. This study shows that although the results of these two methods are in good agreement with each other, the results of TSP 303 are more accurate and higher quality. Also, we believe that using another geophysical method, in addition to TSP 303, could be helpful in making decisions in support of excavation, especially in complicated geological conditions.

scholarly journals Semi-Automatic Identification and Pre-Screening of Geological–Geotechnical Deformational Processes Using Persistent Scatterer Interferometry Datasets

2019 ◽  
Vol 11 (14) ◽  
pp. 1675 ◽  
Author(s):  
Tomás ◽  
Pagán ◽  
Navarro ◽  
Cano ◽  
Pastor ◽  
...  
Keyword(s):  
Regional Scale ◽  
Central Italy ◽  
Geographical Information ◽  
External Information ◽  
Automatic Identification ◽  
Persistent Scatterer Interferometry ◽  
Active Deformation ◽  
Persistent Scatterers ◽  
Persistent Scatterer ◽  
Map Scale

This work describes a new procedure aimed to semi-automatically identify clusters of active persistent scatterers and preliminarily associate them with different potential types of deformational processes over wide areas. This procedure consists of three main modules: (i) ADAfinder, aimed at the detection of Active Deformation Areas (ADA) using Persistent Scatterer Interferometry (PSI) data; (ii) LOS2HV, focused on the decomposition of Line Of Sight (LOS) displacements from ascending and descending PSI datasets into vertical and east-west components; iii) ADAclassifier, that semi-automatically categorizes each ADA into potential deformational processes using the outputs derived from (i) and (ii), as well as ancillary external information. The proposed procedure enables infrastructures management authorities to identify, classify, monitor and categorize the most critical deformations measured by PSI techniques in order to provide the capacity for implementing prevention and mitigation actions over wide areas against geological threats. Zeri, Campiglia Marittima–Suvereto and Abbadia San Salvatore (Tuscany, central Italy) are used as case studies for illustrating the developed methodology. Three PSI datasets derived from the Sentinel-1 constellation have been used, jointly with the geological map of Italy (scale 1:50,000), the updated Italian landslide and land subsidence maps (scale 1:25,000), a 25 m grid Digital Elevation Model, and a cadastral vector map (scale 1:5,000). The application to these cases of the proposed workflow demonstrates its capability to quickly process wide areas in very short times and a high compatibility with Geographical Information System (GIS) environments for data visualization and representation. The derived products are of key interest for infrastructures and land management as well as decision-making at a regional scale.

Comprehensive study of the geological structure Verkhneyakovlev deposits of the Tagul field in the process of justifications for operational drilling

2021 ◽  
pp. 85-97
Author(s):  
A. S. Titenkov ◽  
Yu. N. Utyashev ◽  
A. A. Evdoshchuk ◽  
V. A. Belkina ◽  
D. V. Grandov
Keyword(s):  
Complex Structure ◽  
Geological Structure ◽  
Reservoir Rock ◽  
Rock Properties ◽  
Capital Costs ◽  
Complex Geological Structure ◽  
Well Correlation ◽  
Effective Development ◽  
The Cost ◽  
Available Information

Currently, most of the fields being put into development are characterized by a complex geological structure, both in terms of section and in terms of plan. The solution of all geological tasks, including such important ones as the preparation of exploration projects, operation and effective development management, is impossible without creating models that reflect the main features of the variability of target parameters. The construction of adequate models of objects with a complex structure requires the involvement of all available information. The accuracy of the geological model is mostly determined by the accuracy of the well correlation. Paleosols are a new marker for the complex-built layers of the VAk-2 and VAk-3(1) of the Tagul field, which contributes to the validity of the correlation of the section of these layers. The reliability of the model was also improved by the use of the results of facies analysis. This analysis showed that the sedimentation of the studied objects includes channel and floodplain facies. Reservoir rock properties of these facies differ significantly. The updated model is characterized by a reduction in the oil-bearing area and the amount of reserves. The implementation of the model will optimize the project fund of wells and reduce the cost of well intervention. Economically, this means reducing capital costs and increasing the profitability of the project.

Analysis of a database of landslides triggered by the 2016 Central Italy seismic sequence  

2021 ◽  
Author(s):  
Giovanni Forte ◽  
Melania De Falco ◽  
Federica Iannicelli ◽  
Antonio Santo
Keyword(s):  
Central Italy ◽  
Google Earth ◽  
Mountain Range ◽  
Seismic Sequence ◽  
Large Area ◽  
Geometrical Characterization ◽  
Seismic Parameters ◽  
Main Shocks ◽  
Ground Effects ◽  
Transportation Routes

<p>The seismic sequence that struck Central Italy in 2016 was characterized by three main shocks respectively occurred on August 24<sup>th</sup> Mw 6.0; October 26<sup>th</sup> Mw5.9 and October 30<sup>th</sup> Mw 6.5. The seismic sequence caused several ground effects over a large area of ​​the central Apennine mountain range, mainly affecting transportation routes.</p><p>In the aftermath of the sequence, several research groups mapped around 820 landslides involving road cuts in rock and fill slopes over an area of about 2000 km<sup>2</sup> (GEER,ISPRA, C.E.R.I. by Roma La Sapienza). These data are summarized in the CEDIT catalog by Martino et al., (2017), where almost 150, 250 and 420 instability phenomena were respectively triggered by each mainshock. Further updates were carried out by the Authors in the framework of the Reluis projects of the Department of Civil Protection. In particular, other 550 phenomena were mapped by interpretation of aero photos provided by google-earth. For some of the largest ones, field surveys were carried out for mechanical, structural, and geometrical characterization.</p><p>The dataset distribution was analyzed with geological, geomorphological, and seismic parameters, such as lithology, fault distance, landslide run-out, estimates of mobilized volumes, distance from the epicenter, PGA, and damages.</p><p>The triggered events are mainly characterized by Category I of Keefer (1984) classification, namely rockfalls and rockslides. The maximum triggering distance resulted as high as 50 km far from the epicenter. The most affected areas are characterized by ridge crests or flanks of valleys in carbonate rocks.</p><p>This study permitted to highlight the most relevant parameters for the assessment of earthquake-triggered susceptibility for the study area and identify some meaningful and critical case studies for the future development of the research.</p><p> </p>

Chapter 8 Outboard-migrating accretionary orogeny at 1.9–1.8 Ga (Svecokarelian) along a margin to the continent Fennoscandia

2020 ◽  
Vol 50 (1) ◽  
pp. 237-250 ◽  
Author(s):  
Michael B. Stephens
Keyword(s):  
Base Metal ◽  
Regional Scale ◽  
Volcanic Rocks ◽  
Shear Zones ◽  
Strike Slip ◽  
Base Metal Sulphide ◽  
Metal Sulphide ◽  
Time Period ◽  
Ductile Shear Zones ◽  
Strike Slip Movement

AbstractAn intimate lithostratigraphic and lithodemic connection between syn-orogenic rock masses inside the different lithotectonic units of the 2.0–1.8 Ga (Svecokarelian) orogen, Sweden, is proposed. A repetitive cyclic tectonic evolution occurred during the time period c. 1.91–1.75 Ga, each cycle lasting about 50–55 million years. Volcanic rocks (c. 1.91–1.88 Ga) belonging to the earliest cycle are host to most of the base metal sulphide and Fe oxide deposits inside the orogen. Preservation of relict trails of continental magmatic arcs and intra-arc basins is inferred, with differences in the depth of basin deposition controlling, for example, contrasting types of base metal sulphide deposits along different trails. The segmented geometry of these continental magmatic arcs and intra-arc basins is related to strike-slip movement along ductile shear zones during transpressive events around and after 1.88 Ga; late orogenic folding also disturbed their orientation on a regional scale. A linear northwesterly orogenic trend is suggested prior to this structural overprint, the strike-slip movement being mainly parallel to the orogen. A solely accretionary orogenic model along an active margin to the continent Fennoscandia, without any trace of a terminal continent–continent collision, is preferred. Alternating retreating and advancing subduction modes that migrated progressively outboard and southwestwards in time account for the tectonic cycles.

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