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L. Moratto B. Orlecka-Sikora G. Costa P. Suhadolc Ch. Papaioannou C.B. Papazachos 《Tectonophysics》2007,442(1-4):66-82
The maximum expected ground motion in Greece is estimated for shallow earthquakes using a deterministic seismic hazard analysis (DSHA). In order to accomplish this analysis the input data include an homogeneous catalogue of earthquakes for the period 426 BC–2003, a seismogenic source model with representative focal mechanisms and a set of velocity models. Because of the discrete character of the earthquake catalogue and of errors in location of single seismic events, a smoothing algorithm is applied to the catalogue of the main shocks to get a spatially smoothed distribution of magnitude. Based on the selected input parameters synthetic seismograms for an upper frequency content of 1 Hz are computed on a grid of 0.2° × 0.2°. The resultant horizontal components for displacement, velocity, acceleration and DGA (Design Ground Acceleration) are mapped. The maps which depict these results cannot be compared with previously published maps based on probabilistic methodologies as the latter were compiled for a mean return period of 476 years. Therefore, in order to validate our deterministic analysis, the final results are compared with PGA estimated from the maximum observed macroseismic intensity in Greece during the period 426 BC–2003.Since the results are obtained for point sources, with the frequency content scaled with moment magnitude, some sensitivity tests are performed to assess the influence of the finite extent of fault related to large events. Sensitivity tests are also performed to investigate the changes in the peak ground motion quantities when varying the crustal velocity models in some seismogenic areas. The ratios and the relative differences between the results obtained using different models are mapped and their mean value computed. The results highlight the importance in the deterministic approach of using good and reliable velocity models. 相似文献
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Carla Barnaba Giovanna Laurenzano Luca Moratto Monica Sugan Alessandro Vuan Enrico Priolo Marco Romanelli Paolo Di Bartolomeo 《Bulletin of Earthquake Engineering》2014,12(5):2165-2178
Strong-motion data consisting of peak ground acceleration and velocity and 5 % damped response spectra are presented for 46 earthquakes of the Emilia seismic sequence which occurred in the Po Plain (northern Italy) in 2012. The data were recorded by the OGS temporary network installed close to the town of Ferrara following the main shock of May 20, 2012. Ground-motion peak parameters and spectral responses are compared with the ground-motion prediction equation (GMPE) of Bindi et al. (Bull Earthq Eng 9:1899–1920, 2011) for soft soils and reverse faults. Peak ground accelerations are in general in good agreement with those predicted by GMPE, while predicted peak ground velocities underestimate the observed data, especially for stronger events at more distant stations. The response spectra follow the trend in peak ground velocities, with observed values higher than predicted values at longer periods. This behavior has been interpreted as a site effect due to the deep soft alluvial cover of the Po Plain, which promotes ground motion characterized by a large low-frequency spectral content that is not yet well modeled by the Italian GMPE. A peculiar behavior was shown by the event occurring on June 6, 04:08:33 UTC, \(\hbox {M}=4.5\) , located at the eastern edge of the Po Plain, which produced peak ground accelerations exceeding three times the values estimated by attenuation laws. Such a great discrepancy could be related to post-critically reflected S-waves and multiples from the Moho (SmSM). 相似文献
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The first stations of the Friuli Venezia Giulia (NE Italy) Accelerometric Network (Rete Accelerometrica del Friuli Venezia
Giulia—RAF) were installed by the Department of Earth Sciences, University of Trieste, in the early nineties in the framework
of international scientific projects. Today RAF is configured, taking in to account also other network stations operating
in Italy as well as in Austria and Slovenia, to record accelerations at several important sites in the seismic area of Friuli
Venezia Giulia and near its borders with Slovenia and Austria. This allows an immediate estimate of peak ground acceleration
as well as a first evaluation of possible damages. In the year 2000, DST and the Friuli Venezia Giulia Direction of the Civil
Defence signed an agreement for the RAF management and its use for civil defence purposes, like the prompt estimate of the
damage level after an earthquake occurrence, the emergency management, the reconstruction planning, and the validation and
updating of seismic hazard maps. Moreover, RAF recordings are used also for prevention purposes by the civil defence. This
is performed with the computation of real time shake maps, possible ground-shaking scenarios, studies of the physics of the
seismic source, site effects estimates and microzonation analyses. 相似文献
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The ShakeMap software automatically generates maps of the peak ground motion parameters (shakemaps) and of instrumental intensity
soon after an earthquake. Recorded data are fundamental to obtaining accurate results. In case observations are not available,
ShakeMap relies on ground motion predictive equations, but due to unmodelled site conditions or finite fault effects, large
uncertainties may appear, mainly in the near-source area where damage is relevant. In this paper, we aim to account for source
effects in ShakeMap by computing synthetics to be used for integrating observations and ground motion predictive equations
when near-source data are not available. To be effective, the computation of synthetics, as well as of the finite fault, should
be done in near real time. Therefore, we computed rapid synthetic seismograms, by a stochastic approach, including the main
fault features that were obtained through inversion of regional and teleseismic data. The rapidity of calculation is linked
to a number of assumptions, and simplifications that need testing before the procedure can run in automatic mode. To assess
the performance of our procedure, we performed a retrospective validation analysis considered as case study of the M
w = 6.3 earthquake, which occurred in central Italy on April 6, 2009. In that case, the first shakemaps, generated a few minutes
after the earthquake, suffered large uncertainties on ground motion estimates in an area closer to the epicenter due to the
lack of near-field data. To verify our approach, we recomputed shakemaps for the L’Aquila earthquake, integrating data available
soon after the earthquake at different elapse times with synthetics, and we compared our shaking map with the final shakemap,
obtained when all the data were available. Our analysis evidences that (1) when near-source data are missing, the integration
of real data with synthetics reduces discrepancies between computed and actual ground shaking maps, mainly in the near-field
zone where the damage is relevant and (2) the approach that we adopted is promising in trying to reduce such discrepancies
and could be easily implemented in ShakeMap, but some a priori calibration is necessary before running in an automatic mode. 相似文献
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