scholarly journals Radiography of a normal fault system by 64,000 high-precision earthquake locations: The 2009 L'Aquila (central Italy) case study

2013 ◽  
Vol 118 (3) ◽  
pp. 1156-1176 ◽  
Author(s):  
L. Valoroso ◽  
L. Chiaraluce ◽  
D. Piccinini ◽  
R. Di Stefano ◽  
D. Schaff ◽  
...  
Keyword(s):  
High Precision ◽  
Central Italy ◽  
Normal Fault ◽  
Fault System ◽  
Earthquake Locations

scholarly journals Workflow of Digital Field Mapping and Drone-Aided Survey for the Identification and Characterization of Capable Faults: The Case of a Normal Fault System in the Monte Nerone Area (Northern Apennines, Italy)

2020 ◽  
Vol 9 (11) ◽  
pp. 616
Author(s):  
Mauro De Donatis ◽  
Mauro Alberti ◽  
Mattia Cipicchia ◽  
Nelson Muñoz Guerrero ◽  
Giulio F. Pappafico ◽  
...  
Keyword(s):  
Central Italy ◽  
Three Dimensional ◽  
Normal Fault ◽  
Field Work ◽  
Digital Data ◽  
Fault System ◽  
Seismic Profiles ◽  
Postgraduate Students ◽  
Recent Earthquakes

Field work on the search and characterization of ground effects of a historical earthquake (i.e., the Cagli earthquake in 1781) was carried out using terrestrial and aerial digital tools. The method of capturing, organizing, storing, and elaborating digital data is described herein, proposing a possible workflow starting from pre-field project organization, through reiteration of field and intermediate laboratory work, to final interpretation and synthesis. The case of one of the most important seismic events in the area of the northern Umbria–Marche Apennines provided the opportunity to test the method with both postgraduate students and researchers. The main result of this work was the mapping of a capable normal fault system with a great number of observations, as well as a large amount of data, from difficult outcrop areas. A GIS map and a three-dimensional (3D) model, with the integration of subsurface data (i.e., seismic profiles and recent earthquake distribution information), allowed for a new interpretation of an extensional tectonic regime of this Apennines sector, similar to one of the southernmost areas of central Italy where recent earthquakes occurred on 2016.

scholarly journals Surface Faulting Caused by the 2016 Central Italy Seismic Sequence: Field Mapping and LiDAR/UAV Imaging

2018 ◽  
Vol 34 (4) ◽  
pp. 1585-1610 ◽  
Author(s):  
Stefano Gori ◽  
Emanuela Falcucci ◽  
Fabrizio Galadini ◽  
Paolo Zimmaro ◽  
Alberto Pizzi ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Central Italy ◽  
Normal Fault ◽  
Fault System ◽  
Surface Rupture ◽  
Field Mapping ◽  
Central Italy Earthquake ◽  
Levels Of Detail ◽  
Main Fault ◽  
Surface Ruptures

The three mainshock events (M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016) in the Central Italy earthquake sequence produced surface ruptures on known segments of the Mt. Vettore–Mt. Bove normal fault system. As a result, teams from Italian national research institutions and universities, working collaboratively with the U.S. Geotechnical Extreme Events Reconnaissance Association (GEER), were mobilized to collect perishable data. Our reconnaissance approach included field mapping and advanced imaging techniques, both directed towards documenting the location and extent of surface rupture on the main fault exposure and secondary features. Mapping activity occurred after each mainshock (with different levels of detail at different times), which provides data on the progression of locations and amounts of slip between events. Along the full length of the Mt. Vettore–Mt. Bove fault system, vertical offsets ranged from 0–35 cm and 70–200 cm for the 24 August and 30 October events, respectively. Comparisons between observed surface rupture displacements and available empirical models show that the three events fit within expected ranges.

Sequential modelling of the 2016 Central Italy earthquake cluster using multisource satellite observations and quantitative assessment of Coulomb stress change

2020 ◽  
Vol 221 (1) ◽  
pp. 451-466 ◽  
Author(s):  
Qian Xu ◽  
Qiang Chen ◽  
Jingjing Zhao ◽  
Xianwen Liu ◽  
Yinghui Yang ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Central Italy ◽  
Normal Fault ◽  
Satellite Observations ◽  
Fault System ◽  
Potential Zone ◽  
Seismic Zone ◽  
Seismogenic Fault ◽  
Positive Effects ◽  
Sequence Of Events

SUMMARY A sequence of earthquake events consisting of three large shocks occurred in Central Italy from August to October in 2016 with the duration of almost 2 months. The preliminary study on the seismic mechanism suggests that the sequence of events is the result from the activity of the SW dipping Mt Bove–Mt Vettore–Mt Gorzano normal fault system. For investigation and understanding of the coseismic faulting of the seismogenic fault alignment, we collect a set of comprehensive satellite observations including the Sentinel-1A, ALOS-2/PALSAR-2 and GPS data to map the coseismic surface deformation and estimate the source models in this study. The derived faulting model for the first Amatrice event is characterized by two distinct slip asperities suggesting that it is a predominantly normal dip-slip motion with slight strike-slip component. The second event, Visso earthquake is almost a purely normal rupture. The third Norcia event is dominated by the normal dip-slip rupture of the seismogenic fault, and has propagated up to the ground with significant slip. The three faulting models are then utilized to quantify the Coulomb failure stress (CFS) change over the seismic zone. First, the CFS change on the subsequent two seismogenic faults of the earthquake sequence is estimated, and the derived positive CFS change induced by the preceding earthquakes suggests that the early events have positive effects on triggering the subsequent seismicity. We then explore the response relation of the aftershocks including 961 events with magnitudes larger than M 3.0 to the CFS change over the seismic zone. It suggests that the rupture pattern of the aftershocks is similar to the major shocks with predominantly normal dip-slip. To assess the risk of the future seismic hazard, we analyse quantitatively the spatial distribution of aftershock occurrence and CFS transfer at the seismogenic depth, indicating that the ruptures of the three major shocks do partly release the accumulated strain on the associated fault alignment as well as the dense aftershock, but the CFS increase zone with few aftershocks in the southwest of the eastern Quaternary fault alignment of Central Italy poses the potential of further rupture. In particular, the distribution of aftershock migration also suggests that the north extension of the Mt Bove fault is the potential zone with rupture risk.

Shallow structural setting of an active normal fault zone in the 30 October 2016 Mw 6.5 central Italy earthquake imaged through a multidisciplinary geophysical approach.

2020 ◽  
Author(s):  
Fabio Villani ◽  
Stefano Maraio ◽  
Pier Paolo Bruno ◽  
Lisa Serri ◽  
Vincenzo Sapia ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Fault Zone ◽  
Central Italy ◽  
Normal Fault ◽  
Alluvial Fan ◽  
Fault System ◽  
Depth Range ◽  
Inversion Algorithm ◽  
Data Set ◽  
Refraction Tomography

<p>We investigate the shallow structure of an active normal fault-zone that ruptured the surface during the 30 October 2016 Mw 6.5 Norcia earthquake (central Italy) using a multidisciplinary geophysical approach. The survey site is located in the Castelluccio basin, an intramontane Quaternary depression in the hangingwall of the SW-dipping Vettore-Bove fault system. The Norcia earthquake caused widespread surface faulting affecting also the Castelluccio basin, where the rupture trace follows the 2 km-long Valle delle Fonti fault (VF), displaying a ~3 m-high fault scarp due to cumulative surface slip of Holocene paleo-earthquakes. We explored the subsurface of the VF fault along a 2-D transect orthogonal to the coseismic rupture on recent alluvial fan deposits, combining very high-resolution seismic refraction tomography, multichannel analysis of surface waves (MASW), reflection seismology and electrical resistivity tomography (ERT).</p><p>We acquired the ERT profile using an array of 64 steel electrodes, 2 m-spaced. Apparent resistivity data were then modeled via a linearized inversion algorithm with smoothness constraints to recover the subsurface resistivity distribution. The seismic data were recorded by  a190 m-long single array centered on the surface rupture, using 96 vertical geophones 2 m-spaced and a 5 kg hammer source.</p><p>Input data for refraction tomography are ~9000 handpicked first arrival travel-times, inverted through a fully non-linear multi-scale algorithm based on a finite-difference Eikonal solver. The data for MASW were extracted from common receiver configurations with 24 geophones; the dispersion curves were inverted to generate several S-wave 1-D profiles, subsequently interpolated to generate a pseudo-2D Vs section. For reflection data, after a pre-processing flow, the picking of the maximum of semblance on CMP super-gathers was used to define a velocity model (VNMO) for CMP ensemble stack; the final stack velocity macro-model (VNMO) from the CMP processing was smoothed and used for post-stack depth conversion. We further processed Vp, Vs and resistivity models through the K-means algorithm, which performs a cluster analysis for the bivariate data set to individuate relationships between the two sets of variables. The result is an integrated model with a finite number of homogeneous clusters.</p><p>In the depth converted reflection section, the subsurface of the VF fault displays abrupt reflection truncations in the 5-60 m depth range suggesting a cumulative fault throw of ~30 m. Furthermore, another normal fault appears in the in the footwall. The reflection image points out alternating high-amplitude reflections that we interpret as a stack of alluvial sandy-gravels layers that thickens in the hangingwall of the VF fault. Resistivity, Vp and Vs models provide hints on the physical properties of the active fault zone, appearing as a moderately conductive (< 150 Ωm) elongated body with relatively high-Vp (~1500 m/s) and low-Vs (< 500 m/s). The Vp/Vs ratio > 3 and the Poisson’s coefficient > 0.4 in the fault zone suggest this is a granular nearly-saturated medium, probably related to the increase of permeability due to fracturing and shearing. The results from the K-means cluster analysis also identify a homogeneous cluster in correspondence of the saturated fault zone.</p>

scholarly journals Machine-Learning-Based High-Resolution Earthquake Catalog Reveals How Complex Fault Structures Were Activated during the 2016–2017 Central Italy Sequence

2021 ◽  
Vol 1 (1) ◽  
pp. 11-19
Author(s):  
Yen Joe Tan ◽  
Felix Waldhauser ◽  
William L. Ellsworth ◽  
Miao Zhang ◽  
Weiqiang Zhu ◽  
...  
Keyword(s):  
Central Italy ◽  
Normal Fault ◽  
Earthquake Sequence ◽  
Fault System ◽  
Earthquake Catalog ◽  
Earthquake Triggering ◽  
Aftershock Activity ◽  
Arrival Times ◽  
Complex Fault ◽  
Fault Structures

Abstract The 2016–2017 central Italy seismic sequence occurred on an 80 km long normal-fault system. The sequence initiated with the Mw 6.0 Amatrice event on 24 August 2016, followed by the Mw 5.9 Visso event on 26 October and the Mw 6.5 Norcia event on 30 October. We analyze continuous data from a dense network of 139 seismic stations to build a high-precision catalog of ∼900,000 earthquakes spanning a 1 yr period, based on arrival times derived using a deep-neural-network-based picker. Our catalog contains an order of magnitude more events than the catalog routinely produced by the local earthquake monitoring agency. Aftershock activity reveals the geometry of complex fault structures activated during the earthquake sequence and provides additional insights into the potential factors controlling the development of the largest events. Activated fault structures in the northern and southern regions appear complementary to faults activated during the 1997 Colfiorito and 2009 L’Aquila sequences, suggesting that earthquake triggering primarily occurs on critically stressed faults. Delineated major fault zones are relatively thick compared to estimated earthquake location uncertainties, and a large number of kilometer-long faults and diffuse seismicity were activated during the sequence. These properties might be related to fault age, roughness, and the complexity of inherited structures. The rich details resolvable in this catalog will facilitate continued investigation of this energetic and well-recorded earthquake sequence.

Sign in / Sign up

Export Citation Format

Share Document