Italian Earthquakes Research Articles

A Ten-Year Earthquake Occurrence Model for Italy

The recent M w 6.3 destructive L’Aquila earthquake has further stimulated the improvement of the Italian operational earthquake forecasting capability at different time intervals. Here, we describe a medium‐term (10‐year) forecast model for M w≥5.5 earthquakes in Italy that aims at opening new possibilities for risk mitigation purposes. While a longer forecast yielded by the national seismic‐hazard map is the primary component in establishing the building code, a medium‐term earthquake forecast model may be useful to prioritize additional risk mitigation strategies such as the retrofitting of vulnerable structures. In particular, we have developed an earthquake occurrence model for a 10‐year forecast that consists of a weighted average of time‐independent and different types of available time‐dependent models, based on seismotectonic zonations and regular grids. The inclusion of time‐dependent models marks a difference with the earthquake occurrence model of the national seismic‐hazard map, and it is motivated by the fact that, at the 10‐year scale, the contribution of time‐dependency in the earthquake occurrence process may play a major role. The models are assembled through a simple averaging scheme whereby each model is weighted through the results of a retrospective testing phase similar to the ones carried out in the framework of the Collaboratory for the Study of Earthquake Predictability. In this way, the most hazardous Italian areas in the next ten years will arise from a combination of distinct models that place more emphasis on different aspects of the earthquake occurrence process, such as earthquake clustering, historical seismic rate, and the presence of delayed faults capable of large events. Finally, we report new challenges and possible developments for future updating of the model.

Discussion 1 on “Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake” by G.P. Cimellaro, A.M.Reinhorn and A. De Stefano

正The thesis of the paper,which is the object of this Discussion,is that the considerable damage suffered by the Basilica,after the earthquake of L'Aquila in 2009,was the exclusive result of the intervention of seismic improvement of the naves,made in 2000;such

Reply to “Discussion 1 on ‘Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake’ by G.P. Cimellaro, A.M. Reinhorn and A.De Stefano” by Vincenzo Ciampi

Reply to “Discussion 1 on ‘Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake’ by G.P. Cimellaro, A.M. Reinhorn and A.De Stefano” by Vincenzo Ciampi

Discussion 2 on “Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake” by G.P. Cimellaro, A.M. Reinhorn and A. De Stefano

正This discussion will address two aspects found in the paper:lack of proper information and some mistakes. Lack of proper information In Section 2 of the paper,a short review of the seismic events suffered by the Basilica and of the interventions of reconstruction which have followed is presented,but the main effects of these events are not

Reply to “Discussion 2 on ‘Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake’ by G.P. Cimellaro, A.M. Reinhorn and A.De Stefano” by Enzo Cartapati

during the review process; therefore more attention and space was given to the historical background of the device and to the equations describing its behavior. A steel hysteretic device using the same principle was tested and evaluated at the laboratory of the University at Buffalo (of second author), and experimental results indicated that it is a useful and reliable solution for energy dissipation. The steel hysteretic damper is never criticized in the paper; the criticism is directed to the global retrofi t solution which also uses the device. If any statement in the paper raised an ambiguous interpretation, this was not the intent of the authors. The paper by Antonacci et al. (2001) explains the

Seismic Analysis of Historic Masonry Buildings: The Vicarious Palace in Pescia (Italy)

Recent Italian earthquakes have underlined the need for wide monitoring and safety assessment of architectonical heritage. This has emerged also from requirements of the new Italian Technical Recommendations for buildings. Within this subject the paper investigates the seismic vulnerability of a specific monumental masonry building: the Vicarious Palace (Palazzo del Vicario) in Pescia, a small town near Florence. The structural behavior of the Palace was investigated using a finite element model in which the non-linearities of the masonry were considered by proper constitutive assumptions. The seismic behavior was evaluated by the pushover method, according to the Italian Technical Recommendations. The results were compared with the ones obtained by a simplified approach based on the kinematic theorem of limit analysis. Comparisons of the expected seismic demand vs the seismic capacity of the Palace confirm the weakness of this type of building to suffer extensive damage under earthquakes, as frequently observed in similar construction typologies. Additionally, the comprehension of the structural behavior under seismic loading allows the identification of a proper retrofitting strategy.

Applicability of the Decision Matrix of North Eastern Atlantic, Mediterranean and connected seas Tsunami Warning System to the Italian tsunamis

Abstract. After the 2004 Indian Ocean tsunami catastrophe, UNESCO through the IOC (Intergovernmental Oceanographic Commission) sponsored the establishment of Intergovernmental Coordination Groups (ICG) with the aim to devise and implement Tsunami Warning Systems (TWSs) in all the oceans exposed to tsunamis, in addition to the one already in operation in the Pacific (PTWS). In this context, since 2005, efforts have begun for the establishment of TWSs in the Indian Ocean (IOTWS), in the Caribbean area (CARIBE EWS) and in the North Eastern Atlantic, the Mediterranean and Connected Seas (NEAMTWS). In this paper, we focus on a specific tool that was first introduced in the PTWS routine operations, i.e., the Decision Matrix (DM). This is an easy-to-use table establishing a link between the main parameters of an earthquake and the possible ensuing tsunami in order to make quick decision on the type of alert bulletins that a Tsunami Warning Center launches to its recipients. In the process of implementation of a regional TWS for the NEAM area, two distinct DMs were recently proposed by the ICG/NEAMTWS, one for the Atlantic and the other for the entire Mediterranean area. This work applies the Mediterranean NEAMTWS DM to the earthquakes recorded in Italy and compares the action predicted by the DM vs. the action that should be appropriate in view of the observed tsunami characteristics with the aim to establish how good the performance of the Italian TWS will be when it uses the DM for future events. To this purpose, we make use of the parametric catalogue of the Italian earthquakes (CPTI04) compiled in 2004 and the most recent compilation of the Italian tsunami, based on the Italian Tsunami Catalogue of 2004 and the subsequent revisions. In order to better compare the TWS actions, we have identified four different kinds of action coding them from 0 to 3 according to the tsunami severity and have further considered three different distance ranges where these actions apply, that is local, regional and basin-wide, that refer to the distance of the message recipients from the tsunami source. The result of our analysis is that the actions prescribed by the DM are adequate only in 45%–55% of the cases, overestimations are about 37% and underestimations are the rest. As a whole, the predictive ability of the DM is not satisfactory, which implies that recipients have the difficult task in managing bulletins carrying a great deal of uncertainty and on the other hand also suggests that strategies to improve the DM or to go beyond the DM need to be found.

Abruzzo, Italy, Earthquakes of April 2009: Heterogeneous Fault-Slip Models and Stress Transfer from Accurate Inversion of ENVISAT-InSAR Data

Abstract The seismic sequence that occurred in the Abruzzo Apennines near L’Aquila (Italy) in April 2009 caused extensive damage and a large number of casualties (more than 300). The earthquake struck an area in the Italian Apennines chain where several faults, belonging to adjacent seismotectonic domains, create a complex tectonic regime resulting from the interaction among regional stress buildup, local stress changes caused by individual earthquakes, and viscous-elastic stress relaxation. Understanding such complex interaction in the Apennines can lead to a large step forward in the seismic risk mitigation in Italy. The Abruzzo earthquake has been very well recorded by interferometric synthetic aperture radar (InSAR) data, much better than the first Italian earthquake ever recorded by satellites, namely, the 1997 Umbria–Marche earthquake. ENVISAT (ENVIronmental SATellite) data for the Abruzzo earthquake are, in fact, very clear and allow an accurate reconstruction of the faulting mechanism. We present here an accurate inversion of vertical deformation data obtained by ENVISAT images, aimed to give a detailed reconstruction of the fault geometry and slip distribution. The resulting fault models are then used to compute, by a suitable theoretical model based on the elastic dislocation theory, the stress changes induced on the neighboring faults. The correlation of the subsequent mainshocks and aftershocks of the Abruzzo sequence with the volumes undergoing increasing Coulomb stress clearly evidence the triggering effect of coseismic stress changes on further seismicity. Moreover, this analysis put in evidence which seismotectonic domains have been more heavily charged by stress released by the Abruzzo mainshocks. The most important faults significantly charged by the Abruzzo sequence belong to the Sulmona and Avezzano tectonic domains. Taking into account the average regional stress buildup in the area, the positive Coulomb stress changes caused by this earthquake can be seen as anticipating the next earthquakes in the neighboring domains of 15–20 yr.

The analysis of historical seismograms: an important tool for seismic hazard assessment. Case histories from French and Italian earthquakes

AbstractSeismic hazard assessment relies on the knowledge of the source characteristics of past earthquakes. Unfortunately, seismic waveform analysis, representing the most powerful tool for the investigation of earthquake source parameters, is only possible for events occurred in the last 100–120 years, i.e., since seismographs with known response function were developed. Nevertheless, during this time significant earthquakes have been recorded by such instruments and today, also thanks to technological progress, these data can be recovered and analysed by means of modern techniques.In this paper, aiming at giving a general sketch of possible analyses and attainable results in historical seismogram studies, I briefly describe the major difficulties in processing the original waveforms and present a review of the results that I obtained from previous seismogram analysis of selected significant historical earthquakes occurred during the first decades of the XXth century, including (A) the December 28, 1908, Messina straits (southern Italy), (B) the June 11, 1909, Lambesc (southern France) – both of which are the strongest ever recorded instrumentally in their respective countries –and (C) the July 13, 1930, Irpinia (southern Italy) events. For these earthquakes, the major achievements are represented by the assessment of the seismic moment (A, B, C), the geometry and kinematics of faulting (B, C), the fault length and an approximate slip distribution (A, C). The source characteristics of the studied events have also been interpreted in the frame of the tectonic environment active in the respective region of interest. In spite of the difficulties inherent to the investigation of old seismic data, these results demonstrate the invaluable and irreplaceable role of historical seismogram analysis in defining the local seismogenic potential and, ultimately, for assessing the seismic hazard. The retrieved information is crucial in areas where important civil engineering works are planned, as in the case of the single-span bridge to be built across the Messina straits and the ITER nuclear fusion power plant to be built in Cadarache, close to the location of the Lambesc event, and in regions characterized by high seismic risk, such as southern Apennines.

Italian strong motion records in ITACA: overview and record processing

The published version 1.0 of the new Italian strong-motion database ITACA (Italian ACcelerometric Archive, http://itaca.mi.ingv.it) includes to date (December 2010) about 4,000 three-component waveforms up to M 6.9, from more than 1,800 earthquakes up to 6.9, recorded by about 400 stations in the period 1972–2009. The uncorrected and corrected strong motion data are archived and can be retrieved with their metadata, concerning events, stations and waveforms. The aim of this paper is to present the procedures for processing the records included in ITACA, accounting for the heterogeneity of this data set, both in terms of quality and amplitude of records as well as illustrating the main features of the ITACA strong-motion dataset. Later, we focus on the “exceptional” ground-motion records, that we, conventionally, denote as those having peak acceleration and peak velocity larger than 300 cm/s2 and 15 cm/s, respectively. These records are less than 2% of the whole ITACA dataset but they are the most relevant for the seismic hazard and engineering implications. Such large peak values, recorded at distances up to 30 km, are related not only to the strongest Italian earthquakes, but also to events with magnitude down to 4. Furthermore, we investigate the dependence of the largest peak values on horizontal and vertical directions and on source-to-site distance.

Around the World

In science news around the world this week, a judge has decided that seven Italian earthquake scientists and technicians will be tried on charges of manslaughter, Germany and Switzerland have nixed nuclear energy, NASA's next medium-class science mission will bring back dirt from an asteroid, an amended forest law favorable to ranchers and loggers has brought an outpouring of concern from Brazil's environmentalists, and public health experts in Germany are scrambling to bring the world's deadliest outbreak ever of enterohemorrhagic Escherichia coli under control.

Rapid Simulation of Seismic Intensity for Civil Protection Purposes: Two Recent Cases in Italy

After a destructive earthquake, civil protection agencies need to know within a matter of minutes where people who are buried alive by rubble can be found. Moreover, they must also be informed as soon as possible—in a matter of hours—about the scope of the disaster, in order to organize rescue teams, provide emergency aid, set up field hospitals and tents for the homeless or displaced, etc. In addition, a financial estimate of damage must be made available to the government. Finally, fast and easily presentable information must be provided to the world at large; ShakeMap (Wald et al. 1999; Wald et al. 2006) and the Prompt Assessment of Global Earthquakes for Response (PAGER; Earle and Wald 2007) accomplish this task. Governing bodies, and also some experts, end up hoping that these calculation products can provide, in almost real time, results that are so detailed they can even be used for the instant needs of civil protection. In other words, in these times of virtual reality, some people hope that the very first rescue teams and other forms of aid can be sent automatically, based on the coordinates of where the model has predicted the worst damage. Now it is true that there has been an impressive increase in seismic networks and in our ability to produce damage scenarios, but unfortunately, no algorithm has the ability to make virtual reality coincide with true reality. In fact, certain losses are also due to factors not predictable by a model (see Discussion and Conclusions). In this work, we investigate the potentialities and limitations of three types of scenarios, produced after the occurrence of two Italian earthquakes of M 5.2 and 6.3. Five out of six scenarios were of acceptable quality for providing generic information to the public; no scenario was sufficient for …

Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake

The 2009 L’Aquila, Italy earthquake highlighted the seismic vulnerability of historic masonry building structures due to improper “strengthening” retrofit work that has been done in the last 50 years. Italian seismic standards recommend the use of traditional reinforcement techniques such as replacing the original wooden roof structure with new reinforced concrete (RC) or steel elements, inserting RC tie-beams in the masonry and new RC floors, and using RC jacketing on the shear walls. The L’Aquila earthquake revealed the numerous limitations of these interventions, because they led to increased seismic forces (due to greater additional weight) and to deformation incompatibilities of the incorporated elements with the existing masonry walls. This paper provides a discussion of technical issues pertaining to the seismic retrofit of the Santa Maria di Collemaggio Basilica and in particular, the limitations of the last (2000) retrofit intervention. Considerable damage was caused to the church because of questionable actions and incorrect and improper technical choices.

Static stress drop as determined from geodetic strain rates and statistical seismicity

[1] Two critical items in the energetic budget of a seismic province are the strain rate, which is measured geodetically on the Earth's surface, and the yearly number of earthquakes exceeding a given magnitude. Our study is based on one of the most complete and recent seismic catalogs of Italian earthquakes and on the strain rate map implied by a multiyear velocity solution for permanent GPS stations. For each of 36 homogeneous seismic zones we use the appropriate Gutenberg-Richter relation, which is based on the seismicity catalog, to estimate a seismic strain rate, which is the strain rate associated with the mechanical work due to a coseismic displacement. We show that for each seismic zone, the volume storing most of the elastic energy associated with the long-term deformation, and hence the seismic strain rate, is inversely proportional to the static stress drop. The GPS-derived strain rate for each seismic zone limits the corresponding seismic strain rate, and an upper bound for the average stress drop is estimated. We show that the implied regional static stress drop varies from 0.1 to 5.7 MPa for catalog earthquakes in the moment magnitude range [4.5–7.3]. The stress drop results are independent of the regional a and b parameters and heat flow but are very sensitive to the assumed maximum magnitude of a seismic province. The data do not rule out the hypothesis that the stress drop positively correlates with the time elapsed after the largest earthquake recorded in each seismic zone.

Retrospective evaluation of the five-year and ten-year CSEP-Italy earthquake forecasts

On August 1, 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP) launched a prospective and comparative earthquake predictability experiment in Italy. The goal of this CSEP-Italy experiment is to test earthquake occurrence hypotheses that have been formalized as probabilistic earthquake forecasts over temporal scales that range from days to years. In the first round of forecast submissions, members of the CSEP-Italy Working Group presented 18 five-year and ten-year earthquake forecasts to the European CSEP Testing Center at ETH Zurich. We have considered here the twelve time-independent earthquake forecasts among this set, and evaluated them with respect to past seismicity data from two Italian earthquake catalogs. We present the results of the tests that measure the consistencies of the forecasts according to past observations. As well as being an evaluation of the time-independent forecasts submitted, this exercise provides insight into a number of important issues in predictability experiments with regard to the specification of the forecasts, the performance of the tests, and the trade-off between robustness of results and experiment duration. We conclude with suggestions for the design of future earthquake predictability experiments.

Building self-consistent, short-term earthquake probability (STEP) models: improved strategies and calibration procedures

We present here two self-consistent implementations of a short-term earthquake probability (STEP) model that produces daily seismicity forecasts for the area of the Italian national seismic network. Both implementations combine a time-varying and a time-invariant contribution, for which we assume that the instrumental Italian earthquake catalog provides the best information. For the time-invariant contribution, the catalog is declustered using the clustering technique of the STEP model; the smoothed seismicity model is generated from the declustered catalog. The time-varying contribution is what distinguishes the two implementations: 1) for one implementation (STEP-LG), the original model parameterization and estimation is used; 2) for the other (STEP-NG), the mean abundance method is used to estimate aftershock productivity. In the STEP-NG implementation, earthquakes with magnitude up to ML= 6.2 are expected to be less productive compared to the STEP-LG implementation, whereas larger earthquakes are expected to be more productive. We have retrospectively tested the performance of these two implementations and applied likelihood tests to evaluate their consistencies with observed earthquakes. Both of these implementations were consistent with the observed earthquake data in space: STEP-NG performed better than STEP-LG in terms of forecast rates. More generally, we found that testing earthquake forecasts issued at regular intervals does not test the full power of clustering models, and future experiments should allow for more frequent forecasts starting at the times of triggering events.

HAZGRIDX: earthquake forecasting model for ML≥ 5.0 earthquakes in Italy based on spatially smoothed seismicity

We present a five-year, time-independent, earthquake-forecast model for earthquake magnitudes of 5.0 and greater in Italy using spatially smoothed seismicity data. The model is called HAZGRIDX, and it was developed based on the assumption that future earthquakes will occur near locations of historical earthquakes; it does not take into account any information from tectonic, geological, or geodetic data. Thus HAZGRIDX is based on observed earthquake occurrence from seismicity data, without considering any physical model. In the present study, we calculate earthquake rates on a spatial grid platform using two declustered catalogs: 1) the Parametric catalog of Italian earthquakes (Catalogo Parametrico dei Terremoti Italiani, CPTI04) that contains the larger earthquakes from MW 7.0 since 1100; and 2) the Italian seismicity catalogue (Catalogo della Sismicita Italiana, CSI 1.1) that contains the small earthquakes down to ML 1.0, with a maximum of ML 5.9, over the past 22 years (1981-2003). The model assumes that earthquake magnitudes follow the Gutenberg-Richter law, with a uniform b-value. The forecast rates are presented in terms of the expected numbers of ML>5.0 events per year for each grid cell of about 10 km × 10 km. The final map is derived by averaging the earthquake potentials that come from these two different catalogs: CPTI04 and CSI 1.1. We also describe the earthquake occurrences in terms of probabilities of occurrence of one event within a specified magnitude bin, DM0.1, in a five year time period. HAZGRIDX is one of several forecasting models, scaled to five and ten years, that have been submitted to the Collaboratory for the Study of Earthquake Probability (CSEP) forecasting center in ETH, Zurich, to be tested for Italy.

Seismic response of a non-symmetric rigid block on a constrained oscillating base

In this paper the influence of base isolation on the behaviour of rigid blocks which represent works of art has been analyzed. The work of art has been modelled with a non-symmetric rigid body, sitting on a base which is connected to a visco-elastic device which represents the passive control system. Two types of security stops have been considered and their effects on the system investigated. The first is able to prevent isolation device breakage by limiting the displacement of the oscillating base to a maximum safety value, the others are introduced to prevent the rigid body from falling off the base. Alternatively the possibility of the rigid block partially coming away from the base was considered. Original equations of motion describing the slide-rocking motion of the rigid block when it is partially outside the support have been obtained. Seismic excitation has been considered by using two registered Italian earthquakes. Collapse due to falling from the oscillating base and due to the overturning of the rigid block has been taken into account. The analysis has been mainly focused on the effects of the friction coefficient, the influence of the slenderness of the body and the role of the two different security stops on the behaviour of the system.

Earthquake-induced landslide displacement attenuation models and application in probabilistic seismic landslide displacement analysis

A landslide displacement (DLL) attenuation model has been developed using spectral intensity and a ratio of critical acceleration coefficient to ground acceleration coefficient. In the development of the model, a New Zealand earthquake record data set with magnitudes ranging from 5.0 to 7.2 within a source distance of 175 km is used. The model can be used to carry out deterministic landslide displacement analysis, and readily extended to carry out probabilistic seismic landslide displacement analysis. DLL attenuation models have also been developed by using earthquake source terms, such as magnitude and source distance, that account for the effects of earthquake fault type, source type, and site conditions. Sensitivity analyses show that the predicted DLL values from the new models are close to those from the Romeo model that was developed from an Italian earthquake record data set. The proposed models are also applied to an analysis of landslide displacements in the Wenchuan earthquake, and a comparison between the predicted and the observed results shows that the proposed models are reliable, and can be confidently used in mapping landslide potential.

Analisi critica su le profondità ipocentrali.

The aim of this study is to point out the difficulties in the analytical determination of hypocentral depth h and the consequent uncertainty in its reliability. The former attempt was realized at world-wide level (december 1964), the latter in the Mediterranean Area (19 reigons, accordingly to the division proposed by Flin, Engdal, Hill, 1974). We considered hypocentral data of the earthquakes occurred in that area during the 1964-1974 decade, with a great care to the h values and their standard deviations. First we pointed out the depth features of every region: afterwards we looked into the standard deviations (E) and their respective h values Data analysis suggested us to calculate a series of exponential functions E = P h- showing standard deviations as a function of focal depth; every region is characterized by a and 3 coefficients calculated by a least squares fit. We analysed results and also made an attempt to explain the standard deviations scatter. We also made an attempt by only Italian earthquakes data (ioining the four sections Northern, Central, Southern Italy, and Sicily), and we calculated the t = f(h) function. Both the world-wide analysis and the Mediterranean one pointed out some interesting elements. — Focal depth data, even if joined with their standard deviations, are very unrealiable particularly for crustal earthquakes; in that case standard deviations often are too large and focal depth lose their physical meaning. — In the upper mantle the data are more reliable. Obviously the choise of the travel-times used to calculate focal depth influences data reliability, particularly in the most heterogeneous layers in the crust.