ALBERT

Beschreibung: We find that geodetic strain rate (SR) integrated with the knowledge of active faults points out that hazardous seismic areas are those with lower SR, where active faults are possibly approaching the end of seismic cycle. SR values estimated from GPS velocities at epicentral areas of large historical earthquakes in Italy decrease with increasing elapsed time, thus highlighting faults more prone to reactivation. We have modelled an exponential decrease relationship between SR and the time elapsed since the last largest earthquake, differencing historical earthquakes according to their fault rupture style. Then, we have estimated the characteristic times of relaxation by a non-linear inversion, showing that events with thrust mechanism exhibit a characteristic time (~ 990 yr) about three times larger than those with normal mechanism. Assuming standard rigidity and viscosity values we can infer an average recurrence time of about 600 yr for normal faults and about 2000 yr for thrust faults.

Beschreibung: We describe the main structure and outcomes of the new probabilistic seismic hazard model for Italy, MPS19 [Modello di Pericolosità Sismica, 2019]. Besides to outline the probabilistic framework adopted, the multitude of new data that have been made available after the preparation of the previous MPS04, and the set of earthquake rate and ground motion models used, we give particular emphasis to the main novelties of the modeling and the MPS19 outcomes. Specifically, we (i) introduce a novel approach to estimate and to visualize the epistemic uncertainty over the whole country; (ii) assign weights to each model components (earthquake rate and ground motion models) according to a quantitative testing phase and structured experts’ elicitation sessions; (iii) test (retrospectively) the MPS19 outcomes with the horizontal peak ground acceleration observed in the last decades, and the macroseismic intensities of the last centuries; (iv) introduce a pioneering approach to build MPS19_cluster, which accounts for the effect of earthquakes that have been removed by declustering. Finally, to make the interpretation of MPS19 outcomes easier for a wide range of possible stakeholders, we represent the final result also in terms of probability to exceed 0.15 g in 50 years.

Beschreibung: The INGV RING research infrastructure is based on a permanent GNSS network developed to measure deformation at different spatial and temporal scales in the Mediterranean region. The network (http://ring.gm.ingv.it/) consists of ~250 real-time transmitting remote sites, using standard RTCM format, towards the Irpinia acquisition centres (Southern Italy). Data streaming is managed by a Ntrip Caster (https://igs.bkg.bund.de/ntrip/bkgcaster), whose sourcetable is synchronized with the RING database, thus guaranteeing reliable metadata for the analysis. Within the EWRICA project, the real-time data analysis is performed by using the RTPPP software (Ge et al.,2012) that provides different Precise Point Positioning products with increasing accuracies (standard PPP, PPP-AR and PPP-RA). On 24-h data, the ambiguity resolution (PPP-AR) and the regional augmentation (PPP-RA) allows accuracies of ~1 cm and ~3 cm for the horizontal and vertical components, respectively, at the best sites. Using shorter sliding windows (i.e. 60 s or 120 s, thus simulating a real-time situation), the accuracies are ~0,5 cm and ~1 cm for horizontal and vertical components, respectively. We also tested a homemade algorithm able to detect co-seismic static offsets in real-time in a simulated real-time strategy. The first results make the RING real-time solutions a potential contribution to be tested in earthquake and tsunami warning systems in Italy and surrounding regions. We will show the RING architecture, from the data to the PPP results, an evaluation of the uncertainties, and some examples of offset detection for recent earthquakes.

Beschreibung: The brittle-ductile transition (BDT) separates the lower crust where deformation occurs in steady-state regime, from the upper crust where it is rather dominated by stick-slip. The fault hangingwall above BDT accumulates elastic energy during the interseismic period, without significant evidence of surface strain rate Faults activate in areas of high strain rate gradients along the segments with lower strain rates Fluid discharge varies as a function of the tectonic setting The phenomenology gives insights for the parameters to be monitored in earthquake forecasting

Beschreibung: Italian Presidenza del Consiglio dei Ministri - Dipartimento della Protezione Civile (DPC) within the INGV-DPC 2007-2009 agreement(project S1), Sapienza University and CNR-Eurocores-TopoEurope.

Beschreibung: Unpublished

Beschreibung: Brisbane Australia

Beschreibung: 3.2. Tettonica attiva

Beschreibung: open

Beschreibung: It is commonly believed that the Po Plain is an area of low seismic haz- ard. This conclusion is essentially a combination of two factors: (1) the historical record of earthquakes, which shows a relatively small number of events of moderate magnitude, and only two significant earthquakes, which occurred in the Middle Ages; and (2) the lack of ad-hoc research on the geology of earthquakes in this area, as although many studies have highlighted the local Quaternary tectonics, only a very few of them have discussed the observed evidence in terms of seismic hazard. In contrast, the data presented in the present study strongly suggest that the level of earthquake hazard in the Po Plain is comparable to that of the well- known seismic areas of the Apennine range, at least in terms of maxi- mum magnitudes. Indeed, the high population density and the concentration of industrial facilities make the Po Plain today one of the more high-risk areas of the Italian territory. The Po Plain represents the foredeep of two growing mountain belts, the southern Alps and the north- ern Apennines. Recently, modern active tectonics studies have been con- ducted along its margins to the south, along the northern Apennine Piedmont belt, and to the northeast, along the eastern southern Alpine Piedmont belt. However, in the central and western sectors of the Po Plain, where the south-verging western southern Alpine front links up with the north-verging Monferrato, Emilia and Ferrara arcs, the Qua- ternary history of tectonic deformation and faulting are still relatively poorly understood. These lie beneath the relatively flat alluvial surface of the Po River, and provide the evidence for paleoseismicity and the result- ing seismic hazard. In this review, we compile the data from the literature to reassess the style and magnitude of the ongoing crustal deformation and the associated earthquake faulting. This includes detailed informa- tion on historical and instrumental seismicity, extensive subsurface in- formation from the ENI industrial exploration, structural interpretation of three regional seismic reflection profiles, analysis of novel global posi- tioning system data, field mapping at selected key areas, and new paleo- seismological investigations. We show that along the western southern Alpine belt between Lake Garda and Lake Maggiore, the active tectonic setting is characterized by a segmented belt of fault-propagation folds. These are 50 km wide, and are controlled by the growth of out-of-se- quence, 10-to-20-km-long, north and south verging thrusts. Regional global positioning system data show ongoing shortening rates of the order of 1 mm/yr. Quaternary fault slip rates typically range between 0.2 mm/yr and 0.4 mm/yr. Pleistocene shortening is obvious not only along the western southern Alpine outer fronts that are buried beneath the Po Plain, but also along the south Alpine foothills between Brescia and Varese. Similar styles and rates of active folding and thrusting have also been documented along the frontal sector of the northern Apennine arcs, from Torino to Ferrara, and along the base of the Apennine mountain front between Piacenza and Bologna. We selected the Brescia and Como sectors in the western southern Alps and the Monferrato and Mirandola structures in the northern Apennines as examples to illustrate the seismic landscape of the study area, in terms of typical active structural, geo- morphic and paleoseismic features. We argue that the level of earthquake hazard in the Po Plain is comparable to that of the Apennine range. On May 20, 2012, a few days after this review was formally accepted for pub- lication, a M W 5.9 earthquake ruptured the Mirandola structure. The seismic sequence following this mainshock is ongoing, and we have added further information about this event (updated on June 3rd, 2012), which substantially confirms the conclusions arrived at here.

Beschreibung: Published

Beschreibung: 969-1001

Beschreibung: 3.2. Tettonica attiva

Beschreibung: JCR Journal

Beschreibung: open

Beschreibung: Field surveys performed by different research groups after the April 6, 2009 L’Aquila earthquake (Mw 6.1; CHIARALUCE et alii, 2011) identified the occurrence of surface faulting along the Paganica normal fault, the causative seismogenic source of the event. The different researchers provided patterns of surface rupture that slightly differ as for the northern and southern portion of the Paganica fault. We here integrated coseismic geodetic data – DInSAR and GPS – with geological observations in order to discriminate what, among the different surface rupture patterns, can be considered as evidence of primary surface faulting. Our results indicated that the Mt. Stabiata-Mt. Castellano faults, to the north, and the San Demetrio fault, to the south – along to which BONCIO et alii (2010) and GALLI et alii (2010) detected ground ruptures, respectively – probably activated solely as sympathetic (sensu SleMMONS & DEPOLO, 1986; DEPOLO, 1994) tectonic structures during the 2009 earthquake. These observations allowed to constrain the extension of the primary surface faulting from the Collebrincioni sector to the area of San Gregorio, thus representing the northern and the southern tips of the Paganica fault, respectively. This defines a total surface rupture length of 12-13 km. Our results highlight the effectiveness of entwining geological and geodetic data to discriminate primary surface faulting from secondary fault ruptures, particularly in cases of moderate magnitude earthquakes, i.e. when modest and rather subtle surface faulting can occur.

Beschreibung: Part of this work has been carried out within the ASI-SIGRIS project, funded by the Italian Space Agency and Istituto Nazionale di Geofisica e Vulcanologia

Beschreibung: Published

Beschreibung: 389-402

Beschreibung: 3.2. Tettonica attiva

Beschreibung: JCR Journal

Beschreibung: restricted

Beschreibung: On April 6, 2009, 01:32:39 GMT, the city of L’Aquila was struck by a Mw 6.3 earthquake that killed 307 people, causing severe destruction and ground cracks in a wide area around the epicenter. Four days before the main shock we augmented the existing permanent GPS network with five GPS stations of the Central Apennine Geodetic Network (CaGeoNet) bordering the L’Aquila basin. The maximum horizontal and vertical coseismic surface displacements detected at these stations was 10.39 ± 0.45 cm and 15.64 ± 1.55 cm, respectively. Fixing the strike direction according to focal mechanism estimates, we estimated the source geometry with a non linear inversion of the geodetic data.Our best fitting fault model is a 13 15.7 km2 rectangular fault,SW-dipping at 55.3 ± 1.8 , consistent with the position of observed surface ruptures. The estimated slip (495 ± 29 mm) corresponds to a 6.3 moment magnitude, in excellent agreement with seismological data.

Beschreibung: Published

Beschreibung: L17307

Beschreibung: 1.9. Rete GPS nazionale

Beschreibung: JCR Journal

Beschreibung: reserved

Beschreibung: Four days before the 6th April M5.8 L’Aquila main-shock, a few GPS receivers recording at 10Hz and 1Hz sampling rates have been set up by INGV in the area affected by the seismic swarm in place by mid-January 2009. These data allowed us to measure for the first time in Italy the dynamic co-seismic displacements with periods ranging from fractions of seconds to several minutes and the full time spectra of the surface co-seismic and early post-seismic deformation with GPS instruments. We use TRACK, the kinematic module of the GAMIT/GLOBK software package, to perform epoch-by-epoch solutions of GPS raw data to obtain 3D time series of surface displacements. TRACK uses floating point LC (L3) observations between pairs of stations and the Mebourne-Wubena Wide Lane combination, with ionospheric constraints, to determine integer ambiguities at each epoch. It requires a fixed station and one, or more, kinematic stations. Usually, the static station is chosen to be far enough from the epicentral area not to be affected by the co-seismic displacements. Since no automatic processing engine exists for TRACK, we built a new shell script, which take full advantage of the Linux CPU-cluster routinely used to analyze 30 seconds GPS data with the GAMIT at INGV-Bologna. The new tool allows to automatically process pairs of stations (i.e., a network) and getting raw time series of several stations simultaneously (depending on the number of cluster nodes available) in a few seconds or minute, depending on the length of the session analyzed. TRACK uses broadcasted, ultra-rapid (containing predictions), rapid and final IGS orbits, thus making quasi-real time processing possible, and actually limited by the access to remote raw high rate GPS data archives. Since that the only two stations recording 10Hz data in the L’Aquila region are located close to the main shock epicenter and no data were available at other sites in Italy, we built a new tool to generate a virtual far field reference station acquiring 10Hz data by interpolating the available 1Hz RINEX data. The interpolated sites permit to properly solve the epoch-by-epoch position of the epicentral sites with the TRACK module. High frequency GPS data are severely affected by multipath noise, which can reach the same magnitude of the co-seismic displacements, and need to be removed consistently. For this reason, we investigate the effect of time and space-wise filters (sidereal and common mode filters) and set up a Matlab tool to perform time and spatial filtering on the raw time series produced by our processing tool. High rate data allow to measure the real static co-seismic offsets, which are not contaminated by early afterslip, which may occur in the next few hours after the earthquake. We analyze 10Hz data from 2 stations (Fig. 1) belonging to the CAGEONET network (Anzidei et al., 2009), and 1Hz data from 75 continuous GPS stations, located in central, southern and northern Italy, for which data are available for the 6th of April. A data quality inspection of the available high rate rinex files has been used to select the reference station, and single baselines solutions have been then resolved. We apply both spatial (common-mode) and temporal (sideral) filters to improve the signal to noise ratio of the observed displacements and estimate the epoch and the static co-seismic offsets. The 3D co-seismic displacement field has been used to invert, using rectangular (Okada, 1985), uniform-slip dislocations embedded in an elastic, homogeneous and isotropic half-space and a constrained, non-linear optimization algorithm (Burgmann et al., 1997), the best fit rectangular dislocation geometry and fault slip distribution, which has been compared with the fault geometry and slip model obtained from the analysis of standard 30 sec 24 hours data.

Beschreibung: Published

Beschreibung: trieste, italy

Beschreibung: 1.9. Rete GPS nazionale

Beschreibung: 3.2. Tettonica attiva

Beschreibung: open

Beschreibung: Italian penisula is a crucial area in the Mediterranean region to understand the active deformation processes along Nubia-Eurasia plate boundary. We present the velocity and strain rate fields of the Italian area derived from continuous GPS observations of more than 300 sites in the time span 1998-2009. The GPS networks were installed and managed by different institutions and for different purposes; altogether they cover the whole country with a mean inter-site distance of about 50 km and provide a valuable source of data to map the present day kinematics of the region. The data processing is performed by BERNESE software ver. 5.0, adopting a distributed session approach, with more than 10 clusters, sharing common stations, each of them consisting of about 40 stations. Daily loosely constrained solutions are routinely produced for each cluster and then combined into a network daily loose solution. Subsequently daily solutions are transformed on the chosen reference frame and the constrained time series are fitted using the complete covariance matrix, simultaneously estimating site velocities together with annual signals and sporadic offsets at epochs of instrumental changes. In this work we provide an updated detailed picture of the horizontal and vertical kinematics (velocity maps) and deformation pattern (strain rate maps) of the Italian area. The results show several crustal domains characterized by different velocity rates and styles of deformation.

Beschreibung: Published

Beschreibung: Vienna (Austria)

Beschreibung: 1.9. Rete GPS nazionale

Beschreibung: open