The 2009 L’Aquila (central Italy) MW6.3 earthquake: Main shock

A MW 6.3 earthquake struck on April 6, 2009 the Abruzzi region (central Italy) producing vast damage in the L’Aquila town and surroundings. In this paper we present the location and geometry of the fault system as obtained by the analysis of main shock and aftershocks recorded by permanent and temporary networks. The distribution of aftershocks, 712 selected events with ML 2.3 and 20 with ML 4.0, defines a complex, 40 km long, NW trending extensional structure. The main shock fault segment extends for 15–18 km and dips at 45 to theSW, between 10 and 2 km depth. The extent of aftershocks coincides with the surface trace of the Paganica fault, a poorly known normal fault that, after the event, has been quoted to accommodate the extension of the area.We observe a migration of seismicity to the north on an echelon fault that can rupture in future large earthquakes.PublishedL183083.1. Fisica dei terremotiJCR Journalreserve

Emergenza “L’Aquila2009”: la campagna di acquisizione dati della Rete Sismica Mobile stand-alone del Centro Nazionale Terremoti

Il 6 aprile 2009 (3.32 locali) un terremoto di Mw 6,3 ha colpito la regione Abruzzo (Italia centrale) producendo un enorme danno alla città de L'Aquila e ai paesi limitrofi causando circa 300 morti e 60.000 senza fissa dimora. A seguito di questo evento sismico, la struttura di Pronto Intervento dell’INGV (Istituto Nazionale di Geofisica e Vulcanologia), si è rapidamente attivata installando in area epicentrale due reti sismiche temporanee (Re.Mo.Tel. in real-time e Re.Mo. in stand-alone) ed il Centro Operativo Emergenza Sismica. In questo lavoro presentiamo come si e’ svolta la campagna sismica della Re.Mo., avente l’obiettivo di acquisire dati di alta qualità e dettaglio per studiare le sorgenti sismiche, l’evoluzione spazio temporale della sequenza e caratterizzare attraverso la microsismicita’ le strutture di faglia attivate ed le proprieta’ del mezzo circostante. Saranno descritte nel dettaglio l’installazione compiuta a poche ore dal mainshock, il suo sviluppo legato all’evoluzione della sequenza sismica, fino alla sua dismissione nel Marzo 2010.Istituto Nazionale di Geofisica e VulcanologiaPublished1.1. TTC - Monitoraggio sismico del territorio nazionaleope

Emergenza “L’Aquila2009”: la campagna di acquisizione dati della Rete Sismica Mobile stand-alone del Centro Nazionale Terremoti

Il 6 aprile 2009 (3.32 locali) un terremoto di Mw 6,3 ha colpito la regione Abruzzo (Italia centrale) producendo un enorme danno alla città de L'Aquila e ai paesi limitrofi causando circa 300 morti e 60.000 senza fissa dimora. A seguito di questo evento sismico, la struttura di Pronto Intervento dell’INGV (Istituto Nazionale di Geofisica e Vulcanologia), si è rapidamente attivata installando in area epicentrale due reti sismiche temporanee (Re.Mo.Tel. in real-time e Re.Mo. in stand-alone) ed il Centro Operativo Emergenza Sismica. In questo lavoro presentiamo come si e’ svolta la campagna sismica della Re.Mo., avente l’obiettivo di acquisire dati di alta qualità e dettaglio per studiare le sorgenti sismiche, l’evoluzione spazio temporale della sequenza e caratterizzare attraverso la microsismicita’ le strutture di faglia attivate ed le proprieta’ del mezzo circostante. Saranno descritte nel dettaglio l’installazione compiuta a poche ore dal mainshock, il suo sviluppo legato all’evoluzione della sequenza sismica, fino alla sua dismissione nel Marzo 2010

Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary

Deep Structure of Northern Apennines Subduction Orogen (Italy) as Revealed by a Joint Interpretation of Passive and Active Seismic Data

The Apennines is a well-studied orogeny formed by the accretion of continental slivers during the subduction of the Adriatic plate, but its deep structure is still a topic of controversy. Here we illuminated the deep structure of the Northern Apennines belt by combining results from the analysis of active seismic (CROP03) and receiver function data. The result from combining these two approaches provides a new robust view of the structure of the deep crust/upper mantle, from the back-arc region to the Adriatic subduction zone. Our analysis confirms the shallow Moho depth beneath the back-arc region and defines the top of the downgoing plate, showing that the two plates separate at depth about 40 km closer to the trench than reported in previous reconstructions. This spatial relationship has profound implications for the geometry of the shallow subduction zone and of the mantle wedge, by the amount of crustal material consumed at trench

Change-point analysis ofVP/VSratio time-series using a trans-dimensional McMC algorithm: applied to the Alto Tiberina Near Fault Observatory seismic network (Northern Apennines, Italy)

This article has been accepted for publication in Geophysical Journal International ©: The Authors 2019. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.Time-series of VP/VS ratio have been used to track local changes in elastic properties of rock volumes. Identifying such variations can provide information on the geophysical processes taking place inside a rock volume during the seismic cycle. A value of VP/VS ratio can be computed from traveltime of P and S waves generated from a single local event and it is representative of the value of the VP/VS ratio for the rocks traversed by the seismic ray, between the source and the receiver. It is straightforward, during a seismic sequence, to generate timeseries of VP/VS ratio for events located close together and a single station. Such time-series should be able to monitor temporal variations of elastic parameters in the rock volume. Due to the very small nature of the expected changes in P- and S-wave velocity, the evaluation of VP/VS ratio time-series has been problematic in the past, and subjective choices about, for example the time-averaging scheme applied or event selection for constructing the timeseries, have been proven to strongly affect the outcomes of the analysis. In this contribution, we present the application of a new methodology for a statistical evaluation of changes in VP/VS ratio time-series. The new methodology belongs to the wide class of ‘change-point analysis’ algorithms and is developed in the framework of Bayesian inference. The posterior probability distribution (PPD) of the change-point locations is obtained using a trans-dimensional Markov chain Monte Carlo (trans-D McMC) algorithm, where the existence and number of changepoints is directly dictated by the data themselves. We apply the new algorithm to the seismic catalogue produced by the Alto Tiberina Near Fault Observatory seismic network (Northern Apennines, Italy). Here the high rate of background seismic release and the dense seismic network allow for a robust statistical analysis. The occurrence of change-points in VP/VS timeseries identified with the proposed procedure is represented in space and time. The space–time distributions of change-points in the study area shows a clear peak of change-points following the occurrence of local main events, clustered along the main fault system activated. The robustness of the proposed approach makes it appropriate as an automatic, real-time tool for monitoring rock property changes related to seismic activity.Published1217-12317T. Variazioni delle caratteristiche crostali e precursori sismiciJCR Journa