epicentral distance (km)

Figure 10. a) RSR for the radial component of motion versus epicentral distance andfrequency; b) RSRs for the vertical component of motion versus epicentral distance andfrequency; c) H/V RSR versus epicentral distance and frequency. Strike-section angle equal to80° (from Romanelli and Vaccari, 1999). d) model of S10. The gray scale in part c) isdifferent from the ones in parts a) and b).

19

4.3 Evaluation of the damage potential of synthetic signals

Even though a number of parameters have been proposed in the literature for measuring thecapacity of earthquake ground motion to damage structures, most of them are not consistentwith building damage observed during earthquakes (Uang and Bertero, 1990).

Among all the different parameters proposed for defining the damage potential, perhaps oneof the most promising is the Earthquake Input Energy (Ei) and associate parameters (thedamping energy E^ and the plastic hysteretic energy EH) that has been studied by Uang and

Bertero (1990). This parameter considers the actual behaviour of a structural system anddepends on the dynamic characteristics of both the ground motion and the structure. The inputenergy is a reliable parameter in selecting the most demanding earthquake and in theevaluation of the destructiveness of synthetic signals. Therefore, at a given site the inputenergy permits the selection of the possible critical motions for the response of the structure.However, in order to perform a reliable design, sizing and detailing when the damage can betolerated, the input energy alone is not sufficient.

The fundamental concept in applying energy methods is the transformation of the equationof motion of a viscous damped single-degree-of-freedom (SDOF) system into an energybalance equation in which the input energy to the structure, due to the seismic shaking at thebase is balanced by the energy absorbed in the structure and by the energy dissipated by thestructure. Then, according to the procedures described by Uang and Bertero (1990), theenergy balance equation is given by,

Ei = Ek + E^ + Ea = Ek + E^ + Es + EH (2)

where Ek represents the absolute kinetic energy, E is the damping energy, and Ea is the

absorbed energy that is composed of the recoverable elastic strain energy, Es, and of theirrecoverable plastic hysteretic energy EH.

In a previous work (Decanini and Mollaioli, 1998) the absolute energy equation is used,since this criterion has the advantage that the physical input energy is reflected, in that Eirepresents the work done by the total base shear at the foundation displacement, and it issuitable for the estimation of the energy terms in the range of periods of interest for themajority of the structures. Ei can be expressed by:

dt2 E J dt2 g

where m is the mass, ut = u + ug is the absolute displacement of the mass, and ug is theearthquake ground displacement. In the following the input energy per unit mass, i.e. Ei/m,will be denoted as Ei.

The synthetic signals database that has been assembled for the Eastern Sicily area, whichcan easily be expanded to other earthquake scenarios, can be used as seismic input in asubsequent engineering analysis, at a very low cost/benefit ratio. For the estimation of thedestructive potential of some of the signals calculated for the simplified models (Figure 5),some parameters, obtained from their (a) direct analysis, (b) integration in the time or in thefrequency domain, and (c) the structural (elastic and anelastic) response, have beeninvestigated by Decanini et al. (1999).

20

20 16 150 f

9 0

Lavasp=2.24g/cm3<x= 1700 m/s P = 350 m/s

ClaysI Aa p= 2.06 g/cm3

a= 1700 m/s |3 = 650m/s

M 2 M l M O

SandsI Sg p= 2.02 g/cm3

a= 1300 m/s p= 350 m/s

18.0 km 17.0 km1

14.0 km 0- i H Model MO

epicentral distance

Figure 11. Simplified model adopted for the first 18 km of section S4; the source is buried inthe bed rock.

Using the model of Figure 11, corresponding to the simplified model of S4 (see Figure 5)the synthetic signals, for the transverse component of motion (SH problem), were calculatedat a series of equally spaced sites. The distance between each site is 200 m and the totalnumber of computed signals is 20: 15 are calculated on the local model Ml (lavas) and 5 onM2 (sands and clays).

On the basis of the parameters characterizing the earthquake destructiveness power, derivedfrom the available strong motion records, the results show that the synthetic signals providean energy response which is typical of accelerograms recorded on intermediate-firm soil, at adistance from the causative fault between 12 km and 30 km, and a magnitude between 6.5 and7.1. Figure 12 shows a comparison between the elastic input energy of three synthetic signals(synth_l, synth_3 and synth_5), evaluated for a damping ratio equal to 5%, and twoaccelerograms (Santa Cruz UCSC/Lick Obs. Elect. Lab., UcscO; and Gilroy # 1, GavilanCollege, Water Tower, Gav. Tower 90) recorded during the Loma Prieta earthquake (1989,M=7.1) on firm soil (SI) and at distances from the surface projection of the causative fault(Df) equal to 15 and 16 km, respectively. It can be observed that the frequency content isalmost the same in both cases, and the maximum values of Ei are concentrated within therange of periods 0.3 < T < 0.5 s. Therefore, distances from the causative fault being equal, thesynthetic signals provide an elastic energy comparable to that obtained from records taken onfirm soil for a magnitude approximately equal to 7.1.

A nice confirmation of the agreement between synthetic and observed spectra is shown inFigure 13, where the response spectra of the first signal is plotted, together with the mean andthe mean plus one standard deviation (SD) of the response spectra of all the signals, and thedesign input energy spectrum proposed by Decanini and Mollaioli (1998) for a soil SI, for adistance 12 < Df< 30 km, and a magnitude 6.5 < M < 7.1. Both the spectral shapes and themaximum values of the input energy of the synthetic signals are consistent with the designspectrum, even though the spectra of the synthetic signals appear to be more concentratedaround their maximum values.

21

E i (cmVs2) - % = 5%

-Gav. Tower 90-Ucsc 0-synth_l- synth_3synth_5

Figure 12. Elastic Ei (cm2/s2) spectra. Comparison between synthetic signals and strongmotion records of Loma Prieta earthquake (1989), Soil SI (from Decanini et al., 1999).

E i (cmVs2) - § = 5%

-Design• syn th lmeanmean+lSD

Figure 13. Elastic Ei (cm2/s2) spectra. Comparison between synthetic signals and design inputenergy spectrum (firm soil SI, 12 < Df < 30 km, 6.5 < M < 7.1) (from Decanini et al., 1999).

5. NON-SYNCHRONOUS SEISMIC EXCITATION OF LONG STRUCTURES

Commonly in the engineering analysis practice, a stochastic model is adopted for the spatialvariability of the ground motion, describing the out-of-phase effects in terms of so-calledcoherency functions. The limitation of such an approach is that the incoherence effect, thewave-passage effect and the local effect are described separately by statistical spectral modelsthat are stationary in time and homogeneous in space.

The theoretical approach, based on the computation of synthetic seismograms, show how thelateral heterogenities can produce strong spatial variations in the ground motion even at smallincremental distances, that can be hardly accounted for by stochastical models. In absoluteterms, the differential motion amplitude is comparable with the input motion amplitude whendisplacement, velocity and acceleration domains are considered. The availability of reliabledata about the geometry and mechanical properties of the medium and about the seismicsources is, in general, assured by the preliminary studies that are required for the constructionof long structures and therefore the deterministic calculations of ground motion is possible.

In the following, the state of the art of the procedure is described showing the very recent

22

numerical experiments carried out for an in-progress EC project: "Advanced methods forassessing the seismic vulnerability of existing motorway bridges" (VAB), to assess theimportance of non-synchronous seismic excitation of long structures. The project focuses onthe "Talubergang Warth" of the Austrian Southern Motorway and the working programcomprises the following tasks: dynamic in-situ testing of the bridge, development andcalibration of linear and nonlinear numerical models, pseudodynamic testing of large bridgepiers in ELSA facility, computation of site-relevant synthetic accelerograms, development ofsimplified analysis tools for assessing the seismic vulnerability of complete bridges anddevelopment of seismic retrofitting measures to improve bridge reliability.

To consider both realistic source and structural models, including topographical features, thehybrid method, that combines the modal summation and the finite difference technique (Fahet al., 1993, 1994) and optimises the use of the advantages of both methods, is used. Wavepropagation is treated by means of the modal summation technique from the source to thevicinity of the local, heterogeneous structure that we may want to model in detail. A laterallyhomogeneous anelastic structural model is adopted, that represents the average crustalproperties of the region. The generated wavefield is then introduced in the grid that definesthe heterogeneous area and it is propagated according to the finite differences scheme (seeFigure 14). With this approach, source, path and site effects are all taken into account, and itis therefore possible a detailed study of the wavefield that propagates at large distances fromthe epicentre.

Distance from the source

Q Source

1A

_

4

: ' .'.7 :~/"c. . '

'pi'vr'il Layered**^ j j Structure

.:^£,.:J 1

* ^ l'////////////////A

*' t* *

LArtificial boundaries, limiting thefinite-difference grid.

Zone of high attenuation, whereA Q is decreasing linearly toward

the artificial boundary.

A Receiver

Adjacent grid lines, where theincoming wave field is introducedinto the FD-model. The wavefield has been computed with themode summation technique. Thetwo grid lines are transparent forbackscattered waves.

Figure 14. Scheme of the hybrid (modal summation plus finite differences scheme) method.

In the hybrid scheme the local heterogeneous model has been coupled with the averagebedrock model. The minimum S-wave velocity in the model is 220 m/s, therefore the mesh

23

used for the finite differences is defined with a grid spacing of 3 m. This allows to carry outthe computations at frequencies as high as about 8 Hz. The synthetic time signals(displacements, velocity and accelerations) have been calculated for the three components ofmotion, adopting a seismic source double-couple model whose parameters are listed in Figure15. In order to have a conservative estimation of the differential motion along the bridge, thesource is located in the same plane that contains the cross-section. Figure 15 contains theacceleration time series corresponding to the radial component of motion and a seismicmoment of 1013 N/m. The figure shows how the lateral heterogeneities can produce strongspatial variations in the ground motion even at small incremental distances (the distancebetween two adjacent signals is approximately ten meters). Source finiteness is taken intoaccount by properly weighting the source spectrum using the scaling laws of Gusev (1983), asreported in Aki (1987). The working magnitude is 5.5 (seismic moment equal to 1.8 1017Nm)and corresponds to the largest, and nearest to the "Taltibergang Warth", recorded event.

The differential motion of each pier with respect to the first one, as well as the one withrespect to the preceding pier, has been computed. The results show that the differential motionamplitude is comparable with the input motion amplitude when displacement, velocity andacceleration are considered. As an example, Figure 16 shows the synthetic accelerations(bottom row) and the differential motion, with respect to the preceding pier (middle row) aswell as the one with respect to the first pier (top row), at the sites corresponding to the pierslocation, for the radial component of motion.

6. CONCLUSIONS

The deterministic calculation of the seismic input makes it unnecessary the traditional pre-defined spectral functions to represent the spatial variability of the ground motion, and itallows, in a very economical way, to study the structural response of extended in-planstructures to highly realistic non-synchronous input. The results can play a fundamental rolein the updating and completion of the scarce existing code provisions (EC8/2), both forconventionally constructed and for isolated structures, that can be very sensitive to a nonadequate estimation of the displacement demand. In fact, the relevance of the displacements atperiods of the order of 10s or so is a key issue for seismic isolation and, in general, forlifelines with large linear dimensions, like bridges and pipelines, where differential motionplays a relevant role on their stability.

The difficulties connected with a correct estimate (or prediction) of the site effect are thedetermination and separation of other factors contributing to the seismic signal: source effect,path effect (including lateral heterogeneity), and possible (but not considered here) non linearsoil response. The theoretical site response estimations that we performed, using differenttypes of seismic motion and different techniques, confirm that the identification of thebehaviour of a site with a set of resonant frequencies could be a very difficult task, especiallywhen the amplification levels seem to be "azimuthally" dependent. Furthermore, our resultsshow that the extension of punctual information to extended sections, i.e. the adoption ofsimplified models, could lead to misleading conclusions concerning the seismic response ofsedimentary basins. The results suggest that, in order to perform an accurate estimate of thesite effects in complicated geometries, it is necessary to make a parametric study that takesinto account the complex combination of the source and propagation parameters.

0

0.163E+01 cm/s2

JOOm

4 6time [s]

10

700 m

Direction of propagation

120E L 220L .. 290:.. 1100

18001900

Bedrock

Vs (m/s)

Source

Lat=16.12°Lon=47.73"h=5 kmstrike=35.8°dip=70°rake=324°distance=8.6 km

Figure 15. Acceleration time series corresponding to the radial component of motion and aseismic source with scalar moment of 1013 N/m.

25

.s bo00

00

6000

1

Figure 16. Synthetic accelerations (bottom row) and the differential motion, with respect tothe preceding pier (middle row) as well as the one with respect to the first pier (top row), atthe sites corresponding to the piers location, for the radial component of motion.

26

ACKNOWLEGEMENTS

We acknowledge the support by CNR grants 96.02986PF54, 97.00540PF54 and CNR98.03238PF54, European Union grants CIPA-CT94-0238, EV5V-CT94-0513 and ENV4-CT96-0491, NATO grant ENVIR. LG 960916 677(96), Italian MURST 40% and 60% funds(1996-1998). Part of this research is a contribution to the UNESCO-IGCP Project 414"Realistic Modelling of Seismic Input for Megacities and Large Urban Areas".

The results concerning the seismic differential motion along the Warth Bridge are part of thestudies that are being carried on for an in-progress EC project: "Advanced methods forassessing the seismic vulnerability of existing motorway bridges" (VAB). The internationalteam is made up of seven partners: Arsenal research, Vienna, Austria; ISMES SP.A,.Bergamo, Italy; ICTP, Trieste, Italy; UPORTO, Porto, Portugal; CIMNE, Barcelona, Spain;SETRA, Bagneaux, France; JRC-ISPRA, EU.

REFERENCES

A.A.V.V., 1999, "Seismic hazard of the Circum-Pannonian region". G. F. Panza, M. Radulianand C.-Y. Trifu editors, PAGEOPH special issue, in press..

Aki, K, 1987, "Strong motion seismology". In M. Erdik and M. Toksoz (eds) Strong groundmotion seismology, NATO ASI Series, Series C: Mathematical and Physical Sciences, D.Reidel Publishing Company, Dordrecht, Vol. 204, pp. 3-39.

Alvarez, L., Vaccari, F., Panza, G. F., 1999, "Deterministic seismic zoning of eastern Cuba".PAGEOPH, in press.

Andrews, D. J., 1986, "Objective determination of source parameters and similarity ofearthquakes of different size". In Earthquake Source Mechanics (Das, S., Boatwright, J. andScholz C. H. editors), American Geophysical Union, Washington D.C., 259-268.

Aoudia, A., Vaccari, F., Suhadolc, P., Meghraoui, M., 1999 "Seismogenic potential andearthquake hazard assessment in the Tell Atlas of Algeria". J. of Seismology., in press.

Bard, P.-Y., 1997, "Local effects on strong ground motion: basic physical phenomena andestimation methods for microzoning studies". In SERINA- Seimic Risk: An IntegratedSeismological, Geotechnical and Structural Approach (ITSAK Ed.), Thessaloniki.

Beresnev, I. A., Wen, K. L., 1996, "Nonlinear soil response-a reality?". Bull. Seism. Soc. ofAm., Vol. 86, No. 6, 1964-1978.

Bernard, P., Zollo, A., 1989, "The Irpinia (Italy) 1980 earthquake: detailed analysis of acomplex normal faulting". J. Geophys. Res., 94, 1631-1647.

27

Boatwright, J., Fletcher, J. B., Fumal, T., 1991, "A general inversion scheme for source, siteand propagation characteristics using multiply recorded sets of moderate size earthquakes".Bull. Seism. Soc. Am. , 81 , 1754-1782.

Borcherdt, R. D., 1970, "Effects of local geology on ground motion near San Francisco Bay".Bull. Seism. Soc. Am., 60, 29-61.

Boschi, E., Ferrari, G., Gasperini, P., Guidoboni, E., Smriglio, G., Valensise, G., 1995,"Catalogo dei forti terremoti in Italia dal 461 a.C. al 1980". ING-SGA, Roma, CD-ROM.

Bus, Z., Szeidovitz, G., Vaccari, F., 1999, "Synthetic seismogram based deterministic seismiczoning for the Hungarian part of the Pannonian Basin". PAGEOPH, in press.

Costa, G., Panza, GP., Suhadolc, P., Vaccari, F., 1992 "Zoning of the Italian region withsynthetic seismograms computed with known structural and source information". Proc. 10thWCEE, July 1992, Madrid, Balkema, 435-438.

Costa, G., Panza, GP., Suhadolc, P., Vaccari, F., 1993, "Zoning of the Italian territory interms of expected peak ground acceleration derived from complete synthetic seismograms". J.Appl. Geophys., 30, 149-160.

Decanini, L., Gavarini, C , Oliveto, G., 1993, "Rivalutazione dei terremoti storici della SiciliaSud-Orientale". In:Atti del 6° Convegno Anidis 3, Perugia, Italy 13-15 October 1993: 1101-1110.

Decanini, L., Gavarini, C , Mollaioli, F., 1995, "Proposta di definizione delle relazioni traintensita1 macrosismica e parametri del moto del suolo". Atti del 7° Convegno L'ingegneriasismica in Italia, Vol. 1, 63-72.

Decanini, L., Mollaioli, F., 1998, "Formulation of Elastic Earthquake Input Energy Spectra",Earthquake Engineering and Structural Dynamics, 27,1503-1522.

Decanini, L., Mollaioli, F., Panza, G. F., Romanelli, F., 1999, "The realistic definition of theseismic input: an application to the Catania area". In: Proc. Of Eres 1999 (G. Oliveto andC.A. Brebbia eds), Catania (Italy), 425-434, WIT Press, Boston.

Dravinski, M., G. Ding, Wen, K-L, 1996, "Analysis of spectral ratios for estimating groundmotion in deep basins". Bull. Seism. Soc. of Am., 86, 646-654.

EC 8, 1993, "Eurocode 8 structures in seismic regions - design - part 1 general and building",Doc TC250/SC8/N57A.

Fah, D., Iodice, C , Suhadolc, P., Panza, GP, 1993. "Anew method for the realistic estimationof seismic ground motion in megacities: the case of Rome". Earthquake Spectra, 9, 643-668.

Fah, D., Panza, GP, 1994, "Realistic modelling of observed seismic motion in complexsedimentary basins". Annali di Geofisica, 37, 6, 1771-1797.

28

Fah, D., Suhadolc, P., 1995, "Application of numerical wave-propagation techniques to studylocal soil effects: the case of Benevento (Italy)". Pure and Appl. Geophys, 143, 513-536.

Field, E. H., 1996, "Spectral amplification in a sediment-filled valley exhibiting clear basin-edge-induced wave". Bull. Seism. Soc. of Am., 86, No. 4, 991-1005.

Field, E. H., Jacob, K. H., 1995, "A comparison and test of various site-response estimationtechniques, including three that are not reference-site dependen". Bull. Seism. Soc. of Am.,Vol. 85, No. 4, 1127-1143.

Florsch, N., Fah, D., Suhadolc, P., Panza, GP., 1991. "Complete Synthetic Seismograms forHigh-Frequency Multimode SH-Waves". PAGEOPH, 136 , 529-560.

Geli, L., Bard, P.-Y., Jullien, B., 1988, "The effect of topography on earthquake groundmotion: a review and new results". Bull. Seism. Soc. Am., 78,42-63.

GNDT, 1997, "Progetto Catania - Caratterizzazione geotecnica del territorio comunale diCatania a fini sismici". GNDT, Milano.

Gusev, A. A., 1983, "Descriptive statistical model of earthquake source radiation and itsapplication to an estimation of short period strong motion". Geophys. J. R. Astron. Soc. 74,787-800.

Kanamori, H., 1977, "The energy release in great earthquakes". J. Geophys. Res. 82, 2981-2987.

Konno, K., Ohmachi, T., 1998, "Ground-motion characteristics estimated from spectral ratiobetween horizontal and vertical components of microtremor". Bull. Seism. Soc. Am., 88, N.1,228-241.

Lachet, C , Bard, P.-Y., 1994, "Numerical and theoretical investigations on the possibilitiesand limitations of Nakamura's technique". J. Phys. Earth, 42, 377-397.

Langston, C. A., 1979, "Structure under Mount Rainier, Washington, inferred fromteleseismic body waves".J. Geophys. Res., 84, 4749-4762.

Lermo, J., Chavez-Garcia, F. J., 1993, "Site effect evaluation using spectral ratios with onlyone station". Bull. Seism. Soc. Am., 83, 574-1594.

Lungu, D., Cornea, T., Craifaleanu, I., Aldea, A., 1996, "Seismic zonation of Romania basedon uniform hazard response". Proc. Fifth Int. Conference on Seismic Zonation, Oct. 17-19,1995, Nice, France.

Manos, G.C., Demosthenous, M., 1992, "Design of R.C. structures according to the GreekSeismic Code Provisions". Bull, of IISEE, 26, 559-578.

Markusic, S., Suhadolc, P., Herak, M., Vaccari, F., 1999, "A contribution to seismic hazardassessment in Croatia from deterministic modelling". PAGEOPH., in press.

29

Marrara, F., Suhadolc, P., 1998, "Observation and modeling of site effects in the Volvi basin,Greece". In: K. Irikura, K. Kudo, H. Okada and T. Sasatani, Eds., The effects of surfacegeology on Seismic Motion, Balkema, Rotterdam, The Netherlands, pp. 973-980.

Moldoveanu, C.L., Panza, GP., 1999, "Modelling for micronization purposes, of the seismicground motion in Bucharest, due to the Vrancea earthquake of May 30, 1990". In: F. Wenzelet al. (Editors), Vrancea earthquakes: Tectonics, Hazard and Risk Mitigation, 85-97.

Molin, D., Stucchi, M., Valensise, G., 1996, "Massime intensita macrosismiche osservate neicomuni italiani". Dipartimento della Protezione Civile. GNDT, ING, SSN, Roma.

Nakamura, Y., 1989, "A method for dynamic characteristics estimation of subsurface usingmicrotremor on the ground surface". Q. Rept. Railway Tech. Res. Inst, 30, 1, 25-33.

Nunziata, C , Fah, D., Panza, G. F., 1995, "Mitigation of seismic hazard of a megacity: thecase of Naples". Annali di Geofisica, 38, 649-661.

Orozova-Stanishkova, I.M., Costa, G., Vaccari, F., Suhadolc, P., 1996, "Estimates of 1 Hzmaximum acceleration in Bulgaria for seismic risk reduction purposes". Tectonophysics, 258,263-274.

Panza, G. F., 1985, "Synthetic Seismograms: the Rayleigh Waves Modal Summation". J.Geophys. 58, 125-145.

Panza, GJF., Craglietto, A., Suhadolc, P., 1991, "Source geometry of historical eventsretrieved by synthetical isoseismals". Tectonophysics, 193,173-184.

Panza, GP., Vaccari, F., Costa, G., Suhadolc, P., Fah, D., 1996a, "Seismic input modellingfor zoning and microzoning", Earthquake Spectra 12, 529-566.

Panza, GP., Vaccari, F., Cazzaro, R., 1999a. "Deterministic seismic hazard assessment". In F.Wenzel et al. (Eds), Vrancea Earthquakes: Tectonics, Hazard and Risk Mitigation, 269-286.Kluwer Academic Publishers, The Netherlands.

Panza, GP., Vaccari, F., Romanelli, F., 1999b. "The IUGS-UNESCO IGCP Project 414 :Realistic modeling of Seismic Input for Megacities and Large Urban Areas", Episodes, Vol.22 ,Nol .

Pedersen, H., LeBrun, B., Hatzfeld, D., Campillo, M., Bard, P.-Y., 1988, "Ground motionamplitude across ridges". Bull. Seism. Soc. Am., 84, 1786-1800.

Radulian, M., Vaccari, F., Mandrescu, N., Panza, GP., Moldoveanu, C.L., 1999 "Seismichazard of Romania: deterministic approach". PAGEOPH, in press.

Riepl, J., Bard, P.-Y., Hatzfeld, D., Papaioannou, C , Nechtshein, S., 1998, "Detailedevaluation of site-response estimation methods across and along the sedimentary valley ofVolvi (EURO-SEISTEST)", Bull. Sesim. Soc. Am., 88, 488-502.

30

Romanelli, F. Bing, Z., Vaccari, F., Panza, GF., 1996. "Analytical computation of reflectionand transmission coupling coefficients for Love waves", Geophys. J. Int., 125, 132-138.

Romanelli F., Bekkevold J., Panza, GF., 1997. "Analytical computation of couplingcoefficients in non-poissonian media", Geophys. J. Int., 129, 205-208.

Romanelli, F., Vaccari, F., Panza, G. F., 1998a. "Realistic Modelling of ground motion:techniques for site response" estimation. In: Proceedings of 6th U.S. National Conference onEarthquake Engineering, Seattle, U.S.A. 31 May - 4 June 1998, CD-ROM: paper 433.

Romanelli, F., Nunziata, C , Natale, M., Panza, G. F., 1998b. "Site response estimation in theCatania area". In: K. Irikura, K. Kudo, H. Okada and T. Sasatani, Eds., The effects of surfacegeology on Seismic Motion, Balkema, Rotterdam, The Netherlands, pp. 1093-1100.

Romanelli, F., Vaccari, F., 1999, "Site response estimation and ground motion spectralscenario in the Catania Area", JOSE, in press.

Sand, T., Pugliese, A., 1999, "Parametric study on topographic effects in seismic soilamplification". In Earthquake Resistant Engineering Structures II (Oliveto G. and BrebbiaC.A. eds), pp. 321-330, WIT Press, Southampton.

Somerville, P., 1996, "Ground Motions", in Scenario for a magnitude 7.0 earthquake on theHayward fault, EERI, Oakland, pp. 35-42.

Theodulidis, N., Bard, P. Y., Archuleta, R., Bouchon, M., 1996, "Horizontal-to-verticalspectral ratio and geological conditions: the case of Garner Valley downhole array inSouthern California". Bull. Seism. Soc. of Am., 86, No. 2, 306-319.

Uang, C. M., Bertero, V. V., 1990, "Evaluation of seismic energy in structures". EarthquakeEngineering and Structural Dynamics, 19, 77-90.

Vaccari, F., Gregersen S., Furlan M., Panza G. F., 1989, "Synthetic seismograms in laterallyheterogeneous, anelastic media by modal summation of P-SV waves". Geophys. J. Int., 99,285-295.

Vaccari, F., Suhadolc, P., Panza, GF., 1990, "Irpinia, Italy, 1980 earthquake: waveformmodelling of strong motion data". Geophys. J. Int. 101, 631-647.

Zivcic, M., Suhadolc, P., Vaccari, F., 1999, "Seismic zoning of Slovenia based ondeterministic hazard computations". PAGEOPH, in press.

Wang , H., Nisimura, A., 1999, "On the behavior of near-source strong ground motion fromthe seismic records in down-hole array at Hyogoken-Nanbu earthquake". In EarthquakeResistant Engineering Structures II (Oliveto G. and Brebbia C.A. eds), pp. 363-372, WITPress, Southampton.

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