The Campotosto linkage fault zone between the 2009 and 2016 seismic sequences of central Italy: Implications for seismic hazard analysis

In the last decade central Italy was struck by devastating seismic sequences resulting in hundreds of casualties (i.e., 2009-L′Aquila moment magnitude [Mw] = 6.3, and 2016-Amatrice-Visso-Norcia Mw max = 6.5). These seismic events were caused by two NW-SE−striking, SW-dipping, seismogenic normal faults that were modeled based on the available focal mechanisms and the seismic moment computed during the relative mainshocks. The seismogenic faults responsible for the 2009-L′Aquila Mw = 6.3 (Paganica Fault—PF) and 2016-Amatrice-Visso-Norcia Mw max = 6.5 (Monte Vettore Fault—MVF) are right-stepping with a negative overlap (i.e., underlap) located at the surface in the Campotosto area. This latter was affected by seismic swarms with magnitude ranging from 5.0 to 5.5 during the 2009 seismic sequence and then in 2017 (i.e., a few months later than the mainshocks related with the 2016 seismic sequence). In this paper, the seismogenic faults related to the main seismic events that occurred in the Campotosto Seismic Zone (CSZ) were modeled and interpreted as a linkage fault zone between the PF and MVF interacting seismogenic faults. Based on the underlap dimension, the seismogenic potential of the CSZ is in the order of Mw = 6.0, even in the case that all the faults belonging to the zone were activated simultaneously. This has important implications for seismic hazard assessment in an area dominated by the occurrence of a major NW-SE−striking extensional structure, i.e., the Monte Gorzano Fault (MGF). Mainly due to its geomorphologic expression, this fault has been considered as an active and silent structure (therefore representing a seismic gap) able to generate an earthquake of Mw max = 6.5−7.0. However, the geological evidence provided with this study suggests that the MGF is of early (i.e., pre- to syn-thrusting) origin. Therefore, the evaluation of the seismic hazard in the Campotosto area should not be based on the geometrical characteristics of the outcropping MGF. This also generates substantial issues with earthquake geological studies carried out prior to the recent seismic events in central Italy. More in general, the 4-D high-resolution image of a crustal volume hosting an active linkage zone between two large seismogenic structures provides new insights into the behavior of interacting faults in the incipient stages of connection.

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Preliminary results on the response of some springs of the Sibillini Mountains area to the 2016-2017 seismic sequence

Acque Sotterranee-Italian Journal of Groundwater ◽

10.7343/as-2020-450 ◽

2020 ◽

Cited By ~ 1

Author(s):

Davide Fronzi ◽

Francesca Banzato ◽

Stefano Caliro ◽

Costanza Cambi ◽

Carlo Cardellini ◽

...

Keyword(s):

Central Italy ◽

Fault System ◽

Lower Amount ◽

Western Slope ◽

Seismic Events ◽

Seismic Sequence ◽

General Increase ◽

Discharge Data ◽

Groundwater Levels ◽

Western Side

The dynamic of groundwater systems feeding several springs of the Sibillini Mountains was deeply affected by nine Mw 5.0÷6.5 seismic events occurred in central Italy starting from August 2016. The strongest shock occurred on October 30th 2016 about 5 km NNE of Norcia Town, 9 km below the surface, as a result of upper crust normal faulting on the nearly 30 km-long Mt Vettore - Mt Bove fault system, a NW-SE trending, SW-dipping fault system outcropping on the western slope of Mt Vettore, the highest peak of Sibillini Mountains. Soon after this event, a general increase of springs and rivers discharge and groundwater levels was observed both in the Visso and Norcia areas, west of the Sibillini Mountains. In the Visso area the hydrogeological changes due to the seismic sequence exhausted in the 2019, while nowadays both discharges and groundwater levels are still higher than before in the Norcia area. Discharge data of the main springs located east, south-east of the Sibillini Mountains were analysed to verify whether the general increase observed on the western side was associated to a decrease on the eastern and southern-east area. The results show that the springs located on the eastern side and southern-east side of Mt Vettore experienced a significant long-term discharge decrease. In this preliminary work, the analysis of the historical discharge series of the Pescara di Arquata spring (SE of Mt Vettore), and its relationship with the Standard Precipitation Index (SPI) shows that the very low discharge values recorded during the post-seismic period are not associated with SPI as low as documented in the past for similar discharges. Moreover, the stable isotopic composition of Pescara di Arquata water during the post-earthquake period is slightly different from that measured before the seismic events; this suggests that a lower amount of water having more enriched isotopic δ18O content reaches the spring after the seismic sequence. These aspects seem to indicate that groundwater circulation in the southern-east area of Sibillini Mountains has been affected by the 2016-2017 seismic sequence.

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Characteristics of the Seismogenic Faults in the 2018 Lombok, Indonesia, Earthquake Sequence as Revealed by Inversion of InSAR Measurements

Seismological Research Letters ◽

10.1785/0220190002 ◽

2020 ◽

Vol 91 (2A) ◽

pp. 733-744 ◽

Cited By ~ 1

Author(s):

Chisheng Wang ◽

Xinyu Wang ◽

Wenqun Xiu ◽

Bochen Zhang ◽

Guohong Zhang ◽

...

Keyword(s):

Seismic Hazard ◽

Synthetic Aperture Radar ◽

Fault Plane ◽

Earthquake Sequence ◽

Synthetic Aperture ◽

Seismic Gap ◽

Interferometric Synthetic Aperture Radar ◽

Thrust Faults ◽

Aftershock Distribution ◽

Seismogenic Faults

Abstract We invert Interferometric Synthetic Aperture Radar observations for the slip models of the 28 July Mw 6.4, 5 August Mw 6.9, and 19 August Mw 6.9 earthquakes in the 2018 Lombok earthquake sequence. The geodetic measurements and aftershock distribution suggest three south-dipping fault planes with shallow depths for the three events. They are likely associated with the imbricate thrust faults above the main Flores fault. Obvious strike and dip differences were found on the seismogenic faults, which implies probable fault segmentation and explains the cascading fault behaviors with moderate magnitudes. The three events peaked at depths of 12.38, 16.9, and 25.9 km. The estimated moments reach 7.59×1018, 3.33×1019, and 4.61×1019 N·m, equal to Mw 6.52, Mw 6.95, and Mw 7.04 events, respectively. The derived slip distribution covers most of the area in the Lombok fault plane. Future seismic hazard on the seismic gap to the east of Lombok should be noted.

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Recent seismicity before the 24 August 2016 Mw 6.0 Central Italy Earthquake as recorded by the ReSIICO seismic network

Annals of Geophysics ◽

10.4401/ag-7191 ◽

2016 ◽

Vol 59 ◽

Author(s):

Simone Marzorati ◽

Marco Cattaneo ◽

Massimo Frapiccini ◽

Giancarlo Monachesi ◽

Chiara Ladina

Keyword(s):

Central Italy ◽

Seismic Network ◽

Seismic Sequence ◽

L’Aquila Earthquake ◽

Preliminary Results ◽

Seismic Sequences ◽

Seismic Swarm ◽

Central Italy Earthquake ◽

2009 L’Aquila Earthquake ◽

Preparatory Phase

The seismicity of the last four years before the August 24 2016 01:36 UTC MW 6.0 earthquake that struck central Italy is presented with the aim to understand the preparatory phase of the event. In contrast with the 2009 L’Aquila earthquake that was preceded by a seismic sequence and the 2013-2015 Gubbio seismic swarm that, to date, is ended without any strong event, our preliminary results don’t show seismic sequences in the last months previous the mainshock of the August 24 2016 and a low similarity between seismicity clusters in the last four years and the foreshocks.

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The Campotosto Seismic Gap in Between the 2009 and 2016-2017 Seismic Sequences of Central Italy and the Role of Inherited Lithospheric Faults in Regional Seismotectonic Settings

Tectonics ◽

10.1029/2017tc004844 ◽

2018 ◽

Vol 37 (8) ◽

pp. 2425-2445 ◽

Cited By ~ 18

Author(s):

E. Falcucci ◽

S. Gori ◽

C. Bignami ◽

G. Pietrantonio ◽

D. Melini ◽

...

Keyword(s):

Central Italy ◽

Seismic Gap ◽

Seismic Sequences

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Historic City Centers After Destructive Seismic Events, The Case of Finale Emilia During the 2012 Emilia-Romagna Earthquake: Advanced Numerical Modelling on Four Case Studies

The Open Civil Engineering Journal ◽

10.2174/1874149501711011059 ◽

2017 ◽

Vol 11 (1) ◽

pp. 1059-1078 ◽

Cited By ~ 3

Author(s):

Simone Tiberti ◽

Gabriele Milani

Keyword(s):

Seismic Vulnerability ◽

Numerical Models ◽

Central Italy ◽

Actual Condition ◽

Actual State ◽

Seismic Events ◽

Seismic Sequence ◽

Masonry Churches ◽

Historic City ◽

The Village

Introduction:The recent wave of seismic shocks in Central Italy (2016) had once more disastrous consequences for the local monuments, which consisted of old masonry churches and towers. The permanent, seismic-induced damage to cultural heritage has become a serious issue that can no longer be downsized, and questions have been raised about how to satisfactorily assess the vulnerability of such heritage in advance. This paper deals with the investigations into the actual condition of a historic city center partially destroyed by the seismic sequence occurred in May 2012 in Emilia-Romagna. Namely, the case of Finale Emilia – a small to medium-sized village located at the very center of the stricken area – is considered.Methods:Three important heritage masterpieces were numerically analyzed using Finite Element meshes to deepen the knowledge of their seismic vulnerability and try to avoid similar disasters in the future. The first structure is a masonry castle known as “Castello delle Rocche”, which underwent severe damages during the seismic sequence. The second and third examples deal with the structural analysis of two towers, both collapsed due to the quakes: the Fortified Tower of the castle and the Clock Tower of the village. The last analysis is devoted to study the seismic behavior of a medium-sized masonry church (Santa Maria del Rosario), heavily damaged by the seismic sequence and whose bell tower collapsed due to the formation of a hinge at mid-height.Results and Conclusion:Numerical models were created for all the buildings involved, and a variety of advanced analyses were carried out, including nonlinear static and dynamic ones, to have a deep insight into their expected vulnerability, also finding reasonable correspondence between the numerical results and the actual state of damage observed during the surveys made in the aftermath of the seismic events.

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Geological Evidence of Paleo-seismic Events Occurred along the Chelungpu Fault Zone, Taiwan

Terrestrial Atmospheric and Oceanic Sciences ◽

10.3319/tao.2003.14.1.13(t) ◽

2003 ◽

Vol 14 (1) ◽

pp. 013

Author(s):

Aiming Lin ◽

Allen Chen ◽

Toru Ouchi ◽

Tadashi Maruyama

Keyword(s):

Fault Zone ◽

Seismic Events ◽

Geological Evidence ◽

Chelungpu Fault

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Instrumental seismicity of the Amatrice earthquake epicentral area: a review

Annals of Geophysics ◽

10.4401/ag-7283 ◽

2016 ◽

Vol 59 ◽

Author(s):

Maria Grazia Ciaccio

Keyword(s):

Moment Tensor ◽

Central Italy ◽

Central Area ◽

Seismic Sequence ◽

Centroid Moment Tensor ◽

Fault Plane Solutions ◽

Small Magnitude ◽

Epicentral Area ◽

Seismic Sequences ◽

Seismogenic Structures

This study presents a review of the instrumental seismicity of the Norcia-Amatrice area (central Italy) where a still on-going seismic sequence started on August 24th 2016 with a Mw6.0 earthquake.The review is based on the analysis of the seismic catalogs 1981-2016, the CMT (Centroid Moment Tensor) solutions and the TDMT (Time Domain Moment Tensor) solutions, dividing the area into three regions based on the main seismic sequences preceding the Amatrice 2016 mainshock.The seismicity of this region is characterized by different types of activity: single events, minor sequences and swarms with hypocenters within the upper 15 km of the crust. Small-magnitude seismic sequences on March 2007 with maximum Mw3.9, and one earthquake on March 2012, Mw37, not followed by significant seismicity, affected the area east of the Norcia, close to the Mw 5.4 aftershock of the Amatrice 2016 sequence. In the central area, near Accumoli, and in the southern sector close to Amatrice, minor seismic sequences occurred on February 2014 Ml3.5 and on November 2013 Mw3.7 respectively.We integrated hypocentral locations and fault plane solutions to give a first look at the main features of the instrumental seismicity compared to the present seismic sequence in order to relate the seismicity patterns to seismogenic structures of this area of the central Italy.

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Geochemical Characteristics of Soil Gas and Strong Seismic Hazard Potential in the Liupanshan Fault Zone (LPSFZ)

Geofluids ◽

10.1155/2020/4917924 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Huiling Zhou ◽

Hejun Su ◽

Hui Zhang ◽

Chenhua Li ◽

Dongzheng Ma ◽

...

Keyword(s):

Seismic Hazard ◽

Fault Zone ◽

Seismic Activity ◽

Soil Gas ◽

Seismic Gap ◽

Strong Earthquakes ◽

Hazard Potential ◽

The North ◽

Soil Gas Radon ◽

Northern Segment

Eight soil gas measurements were performed in the Liupanshan fault zone (LPSFZ) to observe the concentration and flux of soil gas radon (Rn) and CO2 in October 2017 and October 2018. By combining the historical strong earthquake background and modern seismic activity of the fault zone, the relation between the geochemical distribution characteristics of soil gas and the seismicity of the fault zone was studied herein. Furthermore, the strong seismic hazard potential of the fault zone was discussed. Results show that the concentration of soil gas Rn and CO2 considerably varies in the northern segment of the LPSFZ and is relatively stable in the southern segment. The spatial distribution of the concentration intensity and flux is strong in the north and weak in the south. However, the southern segment of the LPSFZ has a seismic gap that has not been ruptured by strong earthquakes with Ms ≥ 6.5 for the last 1400 years, whereas the seismic activity in the northern segment is relatively frequent, indicating that the fault zone locking degree of the southern segment is higher than that of the northern segment. This observation is completely consistent with the geochemical characteristic distribution of soil gas. Therefore, the southern segment of the LPSFZ should be considered a hazardous segment, where major or strong earthquakes can occur in the future.

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