scholarly journals Instrumental seismicity of the Amatrice earthquake epicentral area: a review 

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

<p><em>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.</em></p><p><em>The review is based on the analysis of the </em><em>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.</em><em></em></p><p><em>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. </em><em>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.</em><em></em></p><p><em>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.</em><em></em></p>

The Global Importance of Continental Seismic Sequences

2020 ◽  
Author(s):  
Richard Walters ◽  
Tim Craig ◽  
Laura Gregory ◽  
Russell Azad Khan
Keyword(s):  
Structural Control ◽  
Initial Conditions ◽  
Moment Tensor ◽  
Central Italy ◽  
Relative Number ◽  
Strike Slip ◽  
Normal Faults ◽  
Centroid Moment Tensor ◽  
Multiple Faults ◽  
Seismic Sequences

&lt;p&gt;Large continental earthquakes necessarily involve cascading rupture of multiple faults or segments (e.g. El Mayor-Cucapah 2010). But these same critically-stressed systems sometimes rupture in drawn-out sequences of smaller earthquakes over days or years (e.g. Central Italy 2016), instead of in a single large event. Due to the similarity in the initial conditions of both scenarios, seismic sequences may be considered as &amp;#8216;failed&amp;#8217; multi-segment earthquakes, whereby cascading rupture is prematurely halted before all available slip deficit is released.&lt;/p&gt;&lt;p&gt;These two modes of strain-release have vastly different implications for seismic hazard. Recent work on the 2016 Central Italy earthquake sequence, which is the first seismic sequence to be studied with modern high-quality geodetic and seismological datasets, showed that complexity in fault structure appeared to exercise a dual control on both the timing and sizes of events throughout this sequence. However, it is unclear if this structural control is common for all continental seismic sequences, how important seismic sequences are for the global seismic moment budget, and how this contribution to moment budget may vary between different tectonic regions.&lt;/p&gt;&lt;p&gt;Here we select shallow crustal continental earthquakes from the Global Centroid Moment Tensor catalog, and identify seismic sequences as agglomerates of clustered pairs of earthquakes where the summed moment (M&lt;sub&gt;0&lt;/sub&gt;) of all aftershocks is greater than 50% of the M&lt;sub&gt;0&lt;/sub&gt; of the first event in the sequence. We analyse the relative number of seismic sequences compared to other earthquakes for normal, reverse, and strike-slip faulting regions, and also calculate the relative M&lt;sub&gt;0&lt;/sub&gt; release of seismic sequences and other earthquakes in these three regimes.&lt;/p&gt;&lt;p&gt;We find that although seismic sequences are equally common by number in all continental tectonic regimes, seismic sequences account for a much higher proportion of M&lt;sub&gt;0&lt;/sub&gt; release for normal faults (~20%) than for reverse faults (~10%), with strike-slip faults intermediate between these two end-members. We also find that the proportion of M&lt;sub&gt;0&lt;/sub&gt; release in seismic sequences is higher for events that occur in regions characterised by a diversity of different earthquake types (e.g. both reverse and strike-slip faulting) than for events that occur in regions characterised by a single earthquake type (e.g. strike-slip faulting only). Together these findings imply that complexity of fault network is an important factor in controlling the occurrence of large-M&lt;sub&gt;0&lt;/sub&gt; seismic sequences, and that &amp;#8216;failed&amp;#8217; multi-segment earthquakes and therefore large-M&lt;sub&gt;0&lt;/sub&gt; seismic sequences are more likely to occur in regions with complex fault networks.&lt;/p&gt;

scholarly journals The Italian Seismic Bulletin: strategies, revised pickings and locations of the central Italy seismic sequence

2016 ◽  
Vol 59 ◽  
Author(s):  
Alessandro Marchetti ◽  
Maria Grazia Ciaccio ◽  
Anna Nardi ◽  
Andrea Bono ◽  
Francesco Mariano Mele ◽  
...  
Keyword(s):  
Focal Mechanism ◽  
Main Shock ◽  
Moment Tensor ◽  
Central Italy ◽  
Seismic Sequence ◽  
Centroid Moment Tensor ◽  
Moment Tensors ◽  
Emergency Group ◽  
First Motion ◽  
New Procedures

<p>The central Italy seismic sequence, started with the Mw = 6.0 Amatrice earthquake on August 24th 2016, is the first significant one after the Italian Seismic Bulletin (BSI) changed its analysis strategies in 2015. These new strategies consist on the release of the BSI every four months, the review of the events with ML ≥ 1.5 and the priority on the review of events with ML ≥ 3.5. Furthermore, in the last year we improved the bulletin tools and made possible the analysis of all the stations whose data are stored in the European Integrated Data Archive (EIDA). The new procedures and software utilities allowed, during the first month of 2016 emergency, to integrate, in the Bulletin, the temporary stations installed by the emergency group SISMIKO, both in real–time transmission and in stand-alone recording. In the early days of the sequence many of the BSI analysts were engaged in the monitoring room shifts, nevertheless at the end of August all events occurred in those days with ML ≥ 4 were analyzed; the largest event recovered and localized is a ML = 4.5 event immediately following the main shock. In September 2016, 83 events with ML ≥ 3.5 were analyzed and re-checked, the number of pickings greatly improved. The focal mechanism of the main shock was evaluated using first motion polarities, and compared with the available Time Domain Moment Tensors and Regional Centroid Moment Tensor. The first eight hours of the day on August 24th, the most critical for the INGV surveillance room, were carefully analyzed: the number of located events increased from 133 to 408. The magnitude of completeness, after the analysis of the BSI, has dropped significantly from about 3.5 to 2.7. The mainshock focal mechanism and the relative locations of the first 8 hours’ aftershocks give clues on the initial fault activation. The seismic sequence in November 2016 is still ongoing; it included a mainshock of Mw = 6.5 on October 30th and 3 events of magnitude greater than 5.0 one on August 24th and two on October 26th.</p>

scholarly journals The first month of the 2016 central Italy seismic sequence: fast determination of time domain moment tensors and finite fault model analysis of the ML 5.4 aftershock

2016 ◽  
Vol 59 ◽  
Author(s):  
Laura Scognamiglio ◽  
Elisa Tinti ◽  
Matteo Quintiliani
Keyword(s):  
Time Domain ◽  
Moment Tensor ◽  
Central Italy ◽  
Model Analysis ◽  
Fault Model ◽  
Normal Faults ◽  
Seismic Sequence ◽  
Moment Tensors ◽  
Finite Fault ◽  
Finite Fault Model

<p>We present the revised Time Domain Moment Tensor (TDMT) catalogue for earthquakes with M_L larger than 3.6 of the first month of the ongoing Amatrice seismic sequence (August 24th - September 25th). Most of the retrieved focal mechanisms show NNW–SSE striking normal faults in agreement with the main NE-SW extensional deformation of Central Apennines. We also report a preliminary finite fault model analysis performed on the larger aftershock of this period of the sequence (M_w 5.4) and discuss the obtained results in the framework of aftershocks distribution.</p>

scholarly journals Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy) seismic sequence

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Silvia Pondrelli ◽  
Simone Salimbeni ◽  
Paolo Perfetti ◽  
Peter Danecek
Keyword(s):  
Moment Tensor ◽  
Mediterranean Area ◽  
Northern Italy ◽  
Seismic Sequence ◽  
Centroid Moment Tensor ◽  
Strong Earthquakes ◽  
Magnitude Range ◽  
The Mediterranean ◽  
Centroid Moment Tensor Solutions

<p>In May 2012, a seismic sequence struck the Emilia region (northern Italy). The mainshock, of Ml 5.9, occurred on May 20, 2012, at 02:03 UTC. This was preceded by a smaller Ml 4.1 foreshock some hours before (23:13 UTC on May 19, 2012) and followed by more than 2,500 earthquakes in the magnitude range from Ml 0.7 to 5.2. In addition, on May 29, 2012, three further strong earthquakes occurred, all with magnitude Ml ≥5.2: a Ml 5.8 earthquake in the morning (07:00 UTC), followed by two events within just 5 min of each other, one at 10:55 UTC (Ml 5.3) and the second at 11:00 UTC (Ml 5.2). For all of the Ml ≥4.0 earthquakes in Italy and for all of the Ml ≥4.5 in the Mediterranean area, an automatic procedure for the computation of a regional centroid moment tensor (RCMT) is triggered by an email alert. Within 1 h of the event, a manually revised quick RCMT (QRCMT) can be published on the website if the solution is considered stable. In particular, for the Emilia seismic sequence, 13 QRCMTs were determined and for three of them, those with M &gt;5.5, the automatically computed QRCMTs fitted the criteria for publication without manual revision. Using this seismic sequence as a test, we can then identify the magnitude threshold for automatic publication of our QRCMTs.</p>

scholarly journals Seismogenesis in Central Apennines, Italy: an integrated analysis of minor earthquake sequences and structural data in the Amatrice-Campotosto area

2009 ◽  
Vol 47 (6) ◽  
Author(s):  
P. Boncio ◽  
G. Lavecchia ◽  
G. Milana ◽  
B. Rozzi
Keyword(s):  
Late Quaternary ◽  
Central Italy ◽  
Normal Fault ◽  
Structural Data ◽  
Integrated Analysis ◽  
Fault Plane Solutions ◽  
Small Magnitude ◽  
Fault Surface ◽  
Displacement Profile ◽  
Earthquake Sequences

We present a seismotectonic study of the Amatrice-Campotosto area (Central Italy) based on an integrated analysis of minor earthquake sequences, geological data and crustal rheology. The area has been affected by three small-magnitude seismic sequences: August 1992 (M=3.9), June 1994 (M=3.7) and October 1996 (M=4.0). The hypocentral locations and fault plane solutions of the 1996 sequence are based on original data; the seismological features of the 1992 and 1994 sequences are summarised from literature. The active WSWdipping Mt. Gorzano normal fault is interpreted as the common seismogenic structure for the three analysed sequences. The mean state of stress obtained by inversion of focal mechanisms (WSW-ENE-trending deviatoric tension) is comparable to that responsible for finite Quaternary displacement, showing that the stress field has not changed since the onset of extensional tectonics. Available morphotectonic data integrated with original structural data show that the Mt. Gorzano Fault extends for ~28 km along strike. The along-strike displacement profile is typical of an isolated fault, without significant internal segmentation. The strong evidence of late Quaternary activity in the southern part of the fault (with lower displacement gradient) is explained in this work in terms of displacement profile readjustment within a fault unable to grow further laterally. The depth distribution of seismicity and the crustal rheology yield a thickness of ~15 km for the brittle layer. An area of ~530 km2 is estimated for the entire Mt. Gorzano Fault surface. In historical times, the northern portion of the fault was probably activated during the 1639 Amatrice earthquake (I = X, M~ 6.3), but this is not the largest event we expect on the fault. We propose that a large earthquake might activate the entire 28 km long Mt. Gorzano Fault, with an expected Mmax up to 6.7.

scholarly journals Brief communication: Co-seismic displacement on 26 and 30 October 2016 (<i>M</i><sub>w</sub> = 5.9 and 6.5) – earthquakes in central Italy from the analysis of a local GNSS network

2017 ◽  
Vol 17 (11) ◽  
pp. 1885-1892 ◽  
Author(s):  
Giorgio De Guidi ◽  
Alessia Vecchio ◽  
Fabio Brighenti ◽  
Riccardo Caputo ◽  
Francesco Carnemolla ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Central Italy ◽  
Geodetic Network ◽  
Satellite System ◽  
Fault System ◽  
Seismic Sequence ◽  
Epicentral Area ◽  
Seismic Displacement ◽  
Fault Trace ◽  
Global Navigation Satellite

Abstract. On 24 August 2016 a strong earthquake (Mw = 6.0) affected central Italy and an intense seismic sequence started. Field observations, DInSAR (Differential INterferometry Synthetic-Aperture Radar) analyses and preliminary focal mechanisms, as well as the distribution of aftershocks, suggested the reactivation of the northern sector of the Laga fault, the southern part of which was already rebooted during the 2009 L'Aquila sequence, and of the southern segment of the Mt Vettore fault system (MVFS). Based on this preliminary information and following the stress-triggering concept (Stein, 1999; Steacy et al., 2005), we tentatively identified a potential fault zone that is very vulnerable to future seismic events just north of the earlier epicentral area. Accordingly, we planned a local geodetic network consisting of five new GNSS (Global Navigation Satellite System) stations located a few kilometres away from both sides of the MVFS. This network was devoted to working out, at least partially but in some detail, the possible northward propagation of the crustal network ruptures. The building of the stations and a first set of measurements were carried out during a first campaign (30 September and 2 October 2016). On 26 October 2016, immediately north of the epicentral area of the 24 August event, another earthquake (Mw = 5.9) occurred, followed 4 days later (30 October) by the main shock (Mw = 6.5) of the whole 2016 summer–autumn seismic sequence. Our local geodetic network was fully affected by the new events and therefore we performed a second campaign soon after (11–13 November 2016). In this brief note, we provide the results of our geodetic measurements that registered the co-seismic and immediately post-seismic deformation of the two major October shocks, documenting in some detail the surface deformation close to the fault trace. We also compare our results with the available surface deformation field of the broader area, obtained on the basis of the DInSAR technique, and show an overall good fit.

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

2020 ◽  
Author(s):  
Emanuele Tondi ◽  
Danica Jablonská ◽  
Tiziano Volatili ◽  
Maddalena Michele ◽  
Stefano Mazzoli ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Fault Zone ◽  
Central Italy ◽  
Seismic Events ◽  
Seismic Gap ◽  
Seismic Zone ◽  
Seismic Sequence ◽  
Geological Evidence ◽  
Seismic Sequences ◽  
Seismogenic Faults

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.

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

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 M<sub>W</sub> 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.

scholarly journals The May-June 2012 Ferrara Arc earthquakes (northern Italy): structural control of the spatial evolution of the seismic sequence and of the surface pattern of coseismic fractures

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Giusy Lavecchia ◽  
Rita de Nardis ◽  
Daniele Cirillo ◽  
Francesco Brozzetti ◽  
Paolo Boncio
Keyword(s):  
Structural Control ◽  
Moment Tensor ◽  
Italian Literature ◽  
Northern Italy ◽  
Surface Pattern ◽  
Spatial Evolution ◽  
Seismic Sequence ◽  
Ongoing Activity ◽  
Centroid Moment Tensor ◽  
Thrust System

The Ferrara 2012 seismic sequence was characterized by two main compressional events, which occurred on May 20 and 29, 2012, with Mw 6.1 and Mw 6.0, respectively (quick Regional Centroid Moment Tensor [RCMT] at http://autorcmt.bo.ingv.it/quicks.html). These events were followed by five events with Mw &gt;5.0 (two on May 20 and three on May 29, 2012) and by hundreds of events of lower magnitudes distributed along a WNW-ESE-elongated area of ca. 500 km2 (ISIDe database at http://iside.rm.ingv.it/ iside/standard/index.jsp.). The ongoing activity of the northward-verging fold-and-thrust structures of the Ferrara-Romagna Arc (Figure 1A) and the eastward-verging Coastal Adriatic Arc (referred to as the Outer Thrust System [OTS] in Lavecchia et al. 2003) has been a debated topic in the Italian literature. […]

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