Enzo Boschi

L'Italia, sede di alcune tra le più antiche civiltà, è una delle zone più sismiche del Mediterraneo. Questi due fatti, uniti all'impatto da sempre prodotto dal terremoto sulla fantasia popolare, hanno portato alla registrazione di notizie attendibili anche di eventi sismici molto antichi. Infatti, già dai primi secoli dopo Cristo, nei maggiori centri di cultura, sono state redatte cronache degli avvenimenti più rilevanti, sia descrivendoli direttamente, sia riportando notizie raccolte. Tuttavia solo a partire dal XIX secolo gli studiosi di sismologia hanno cominciato a estrarre da queste cronache le informazioni riguardanti i terremoti nel tentativo di "scrivere" una storia sismica italiana. Uno dei primi problemi da affrontare è stato quello di classificare gli eventi. Per far questo, non avendo strumenti di misura, era possibile basarsi soltanto sulla valutazione degli effetti prodotti dai terremoti e di conseguenza sono state introdotte le scale macrosismiche ...

... E., Mazza, S., Morelli, A., Ben Sari, D., Najid, D., Benhallou, H., Bezzeghoud, M., Trabeisi, H., Hfaidh, M., Kebeasy, RM and Ibrahim, EM, 1992. ... over the entire frequency spectrum, which, for an event at regional and teleseismic distances, ranges be-tween a few hertz and a ...

... 2. Seismicity analysis On the basis of the tectonic premise described in the previous section, we first analyzed the dis-tribution of seismicity along the zone comprising Montenegro, Albania and northwestern Greece, which is assumed to be the main collision boundary between ...

ABSTRACT We estimate seismological fracture energies from two subsets of events selected from the seismic sequences of L’Aquila (2009), and Northridge (1994): 57 and 16 selected events, respectively, including the main shocks. Following Abercrombie and Rice (Geophys J Int 162: 406–424, 2005), we postulate that fracture energy (G) represents the post-failure integral of the dynamic weakening curve, which is described by the evolution of shear traction as a function of slip. Following a direct-wave approach, we compute mainshock-/aftershock-source spectral ratios, and analyze them using the approach proposed by Malagnini et al. (Pure Appl. Geophys., this issue, 2014) to infer corner frequencies and seismic moment. Our estimates of source parameters (including fracture energies) are based on best-fit grid-searches performed over empirical source spectral ratios. We quantify the source scaling of spectra from small and large earthquakes by using the MDAC formulation of Walter and Taylor (A revised Magnitude and Distance Amplitude Correction (MDAC2) procedure for regional seismic discriminants, 2001). The source parameters presented in this paper must be considered as point-source estimates representing averages calculated over specific ruptured portions of the fault area. In order to constrain the scaling of fracture energy with coseismic slip, we investigate two different slip-weakening functions to model the shear traction as a function of slip: (i) a power law, as suggested by Abercrombie and Rice (Geophys J Int 162: 406–424, 2005), and (ii) an exponential decay. Our results show that the exponential decay of stress on the fault allows a good fit between measured and predicted fracture energies, both for the main events and for their aftershocks, regardless of the significant differences in the energy budgets between the large (main) and small earthquakes (aftershocks). Using the power-law slip-weakening function would lead us to a very different situation: in our two investigated sequences, if the aftershock scaling is extrapolated to events with large slips, a power law (a la Abercrombie and Rice) would predict unrealistically large stress drops for large, main earthquakes. We conclude that the exponential stress evolution law has the advantage of avoiding unrealistic stress drops and unbounded fracture energies at large slip values, while still describing the abrupt shear-stress degradation observed in high-velocity laboratory experiments (e.g., Di Toro et al., Fault lubrication during earthquakes, Nature 2011).

... 1 Dipartimento di Fisica, Settore di Geofisica, Università di Bologna, Viale Berti Pichat 8, 40127 Bologna, Italy. 2 Istituto Nazionale di Geofisica, Via R. Bonghi 11/B, 00184 Roma, Italy. Received 9 December 1983; revised 12 June 1984; accepted 12 June 1984. ...

... DOWNSLOPE FLOW MODELS OF A BINGHAM LIQUID: IMPLICATIONS FOR LAVA FLOWS MICHELE DRAGONI, MAURIZIO BONAFEDE and ENZO BOSCHI Dipartimento di ... of 103 P. Some flood lavas, however, may have greater values of Re (Shaw and Swanson, 1970). ...

ABSTRACT In this paper we describe evidence of strong tectonic deformation affecting two aqueducts of Roman age (II–III century A.D.). The channels are located approximately 20 km northeast of Rome along the ancient Via Tiburtina. Brittle and ductile deformation affects these two structures, including extensional joint systems, NE-oriented faults, and horizontal distortion. This deformation is consistent with right-lateral movement on major N-striking faults, and represents the first evidence that tectonic deformation took place in historical times in the vicinity of Rome, with local strike–slip movement superimposed on a regional extensional fault system.

A continuous global positioning system station (CGPS) provides accurate coordinate time series, while episodic GPS stations (EGPSs), which operate throughout short measurement sessions, are generally used to improve the monitoring spatial density. In an urban environment, EGPSs are typically equipped with removable mounts (topographical tripod or bipod). In this paper, a method is proposed to evaluate vertical surface motions by

The 17 January 2002 fissure eruption of Mount Nyiragongo, Democratic Republic of Congo, produced lava flows which entered and devastated the densely inhabited town of Goma. The 2002 and previous 1977 eruptions demonstrate the high level of volcanic risk in the area. We present an analysis of the susceptibility to lava flow invasion in Goma, by means of computer simulations

A new 2D/3D Lagrangian particle model (named LPAC) for the dynamics of clasts ejected during explosive eruptions is presented. The novelty of the model lies in the one-way coupling of the carrier flow field, given by a Eulerian multiphase flow code, and the particles. The model is based on a simplification of the Basset-Boussinesq-Oseen equation, expressing the Lagrangian equation of

We perform an extensive analysis of the low-degree gravity field harmonics measured by the GRACE mission, in order to find a signature of the postseismic relaxation following the 2004 Sumatra earthquake. We find a statistically significant perturbation in the secular trend of low-degree zonal coefficients (Jl) in correspondence of the 2004 Sumatra earthquake and a similar perturbation, but with weak associated statistical significance, also in the nonzonal coefficients. Technical features and results of such analysis are discussed. The time-dependent postseismic evolution of harmonic coefficients is modeled for various asthenosphere viscosity values, using a theoretical model of global postseismic deformation. The observed change in secular trend is found to be consistent with our modeling results but it cannot be used to discriminate between viscosities. A forward modeling of the perturbations to time-dependent zonal variation rates following the Sumatra earthquake for various asthenospheric viscosities is provided. As a result, an evident signature of the Sumatra earthquake on $\dot{J}$l time series is expected for asthenospheric viscosity values below 1018 Pa s. Therefore, long term $\dot{J}$l time histories from satellite laser ranging will be able to put constraints on the asthenosphere viscosity, if such a signature is evidenced from data or, at least, put lower limits if no significant perturbation will be observed.

... the rose window, still visible on the façade, potentially belonged to the church of Santa Tecla, demolished in 1222; • in 1289 the Accursio residence was used as granary in case of famine or siege, as reported in the “Liber Terminorum”; ...

ABSTRACT Monitoring damaged buildings in an area where an earthquake has occurred requires the use of techniques which provide rapid and safe measurements even in emergency conditions. In particular, remote sensing techniques like terrestrial laser scanning (TLS) can satisfy these requirements, since they produce very dense point clouds in little time and also allow an accurate geometric modeling of observed buildings. Nevertheless, strong constraints on TLS data acquisition geometry, such as acquisition distance and incidence angles, typically characterize an area in seismic emergency conditions. In order to correctly interpret the data, it is necessary to estimate errors affecting TLS measurements in these critical conditions. A reliable estimation can be achieved by means of experiments and numerical simulations aimed at quantifying a realistic noise level, with emphasis on reduction of artifacts due to data acquisition, registration and modeling. This paper proposes a data analysis strategy in which TLS-based morphological maps computed as point-to-primitive differences are created. The method can be easily used for accurate surveying in emergency conditions. In order to demonstrate the proposed method in very diverse situations, it was applied to rapidly detect deformation traces in the San Giacomo Roncole Campanile (Modena), the Asinelli tower (Bologna) and the Cantalovo Church (Verona), three buildings damaged by the Mw 5.9 Emilia Romagna 2012 earthquake (Italy).

Preliminary results of simultaneous ozone and aerosol lidar measurements taken in the period July‐early October 1991 are presented. The main problem for retrieving the ozone profile is the correction of the on and off DIAL signals. The backscattering ratio obtained by the off ...

A simple linear relation can be used to link time averaged discharge rate (TADR) and lava flow area (A). The relation applies to given insulation conditions, as described by the characteristic flow surface temperature (Te), and will vary from case-to-case depending on rheological and topographic influences on flow spreading. Most flows have insulation conditions that change through time, modifying the

... For instance, the Apennines on the west and the Dinarides on the east seem to mark the boundaries of the almost rectangular Adriatic ... the base of the plate, being capable of building up fracture stresses along the plate boundaries (Hanks 1977; Bonafede & Dragoni 1982); it ...

We analysed the time evolution of the decay parameters of the L'Aquila aftershock sequence, neglecting spatial variability. During the first two months after the main shock, the sequence showed quite unusual properties: a particularly slow decay of the aftershock rate that progressively accelerated and a very scarce sensitivity to the occurrence of strong aftershocks. In the first few days, the

ABSTRACT A strike-slip plate boundary is considered with non-uniform strength. Depth-dependent slip on the fault surface is assumed to occur aseismically in the lower fault section, in response to a basal shear stress, and seismically in the brittle upper section. The upper fault section acts as a barrier, preventing aseismic slip from reaching shallower depths. If, however, friction decreases in the proximity of the Earth's surface, brittle fracture may occur beyond the barrier. It is found that, when friction in the uppermost fault section exceeds the applied shear stress, fault slip occurs there with a smaller amplitude than at larger depth. This may explain the discrepancies, which have been sometimes reported, between fault offsets observed at the Earth's surface and fault offsets inferred from seismograms by using simpler dislocation models.

ABSTRACT With the goal of constructing a homogeneous data set of moment magnitudes (Mw) to be used for seismic hazard assessment, we compared Mw estimates from moment tensor catalogues available online. We found an apparent scaling disagreement between Mw estimates from the National Earthquake Information Center (NEIC) of the US Geological Survey and from the Global Centroid Moment Tensor (GCMT) project. We suspect that this is the effect of an underestimation of Mw > 7.0 (M0 > 4.0 × 1019 Nm) computed by NEIC owing to the limitations of their computational approach. We also found an apparent scaling disagreement between GCMT and two regional moment tensor catalogues provided by the 'Eidgenössische Technische Hochschule Zürich' (ETHZ) and by the European-Mediterranean Regional Centroid Moment Tensor (RCMT) project of the Italian 'Istituto Nazionale di Geofisica e Vulcanologia' (INGV). This is probably the effect of the overestimation of Mw < 5.5 (M0 < 2.2 × 1017 Nm), up to year 2002, and of Mw < 5.0 (M0 < 4.0 × 1016 Nm), since year 2003, owing to the physical limitations of the standard CMT inversion method used by GCMT for the earthquakes of relatively low magnitude. If the discrepant data are excluded from the comparisons, the scaling disagreements become insignificant in all cases. We observed instead small absolute offsets (≤0.1 units) for NEIC and ETHZ catalogues with respect to GCMT whereas there is an almost perfect correspondence between RCMT and GCMT. Finally, we found a clear underestimation of about 0.2 units of Mw magnitudes computed at the INGV using the time-domain moment tensor (TDMT) method with respect to those reported by GCMT and RCMT. According to our results, we suggest appropriate offset corrections to be applied to Mw estimates from NEIC, ETHZ and TDMT catalogues before merging their data with GCMT and RCMT catalogues. We suggest as well to discard the probably discrepant data from NEIC and GCMT if other Mw estimates from different sources are available for the same earthquakes. We also estimate approximately the average uncertainty of individual Mw estimates to be about 0.07 magnitude units for the GCMT, NEIC, RCMT and ETHZ catalogues and about 0.13 for the TDMT catalogue.