GNGTS 2014 - Atti del 33° Convegno Nazionale

in Italy suffer directional amplification in the horizontal plane, with a consistent effect between ambient noise and earthquake records. Although the geometry of the surface has an effect on the ground motion, this effect is small (in general a factor of 2, see Lee et al ., 2009). The observed large amplifications at topographic sites are probably related to site-geological as variations of subsurface velocity surface and fractured rocks. The latter would explain also the observed directionality of amplification. A common link between topography and fractures can be found in terms of lineaments which reflect stress state and tectonics at the regional scale, where topography and tectonic features are coaxial. References Anooshehpoor A. and Brune J. N.; 1989: Foam rubber modelling of topographic and dam interaction effects at Pacoma Dam . Bull. Seismol. Soc. Am., 79 , 1347-1360. Bard P.-Y. and Chaljub E.; 2009: Effets of surface topography on seismic ground motion: recent results, remaining issues and needs , AGU09, San Francisco, 17/12/2009. Bard P.-Y. and Tucker B.E.; 1985: Underground and ridge site effects: a comparison of observation and theory . Bull. Seismol. Soc. Am., 75 , 905-922. Ben-Zion Y. and Aki K.; 1990: Seismic radiation from an SH line source in a laterally heterogeneous planar fault zone . Bull. Seismol. Soc. Am., 80 , 971– 994. Boore D.M., Watson-Lamprey J. and Abrahamson N.A.; 2006: Orientation-Independent Measures of Ground Motion . Bull. Seism. Soc. Am., 96- 4A , 1502-1511. Bouchon M.; 1973: Effect of topography on surface motion . Bull. Seismol. Soc. Am., 63 , 615-632. Burjanek J., Gassner-Stamm G., Poggi V., Moore J. R. and Fah D.; 2010: Ambient vibration analysis of an unstable mountain slope . Geophys. J. Int., 180:2 , 820-828. Burjanek J., Moore J.R., Yugsi-Molina F.X. and Fah D.; 2012: Instrumental evidence of normal mode rock slope Vibration . Geophys. J. Int., 188:2 , 559-569. Burjanek J., Edwards B. and Fah D.; 2014a: Empirical evidence of local seismic effects at sites with pronounced topography: a systematic approach . Geophys. J. Int., doi: 10.1093/gji/ggu014, in press. Burjanek J., Fah D., Pischiutta M., Rovelli A., Calderoni G. and Bard, P.-Y., NERA-JRA1 working group: 2014b: Site effects at sites with pronounced topography: overview and recommendations report for EU project NERA , 64 pp, doi: 10.3929/ethz-a-010222426. Çelebi M.; 1987: Topographical and geological amplifications determined from strong-motion and aftershock records of the 3 March 1985 Chile earthquake . Bull. Seismol. Soc. Am., 77 , 1147-1167. Chavez-Garcia F.J., Sanchez L.R. and Hatzfeld D.; 1996: Topographic site effect and HVSR. A comparison between observation and theory . Bull. Seismol. Soc. Am., 5 , 1725-1743. Davis, L. L., and West L. R.; 1973: Observed effects of topography on ground motion . Bull. Seismol. Soc. Am., 63 , 283-298. Del Gaudio V. and Wasowski J.; 2007: Directivity of slope dynamic response to seismic shaking . Geophys. Res. Lett., 34 , L12301. Di Giulio G., Cara F., Rovelli A., Lombardo G. and Rigano R.; 2009: Evidences for strong directional resonances in intensely deformed zones of the Pernicana fault, Mount Etna, Italy . J. Geophys. Res., 114 , doi:10.1029/ 2009JB006393. Falsaperla S., Cara F., Rovelli A., Neri M., Behncke B. and Acocella V.; 2010: Effects of the 1989 fracture system in the dynamics of the upper SE flank of Etna revealed by volcanic tremor data: the missing link? J. geophys. Res., 115(B11306) , doi:10.1029/2010JB007529. Gaffet S. and Bouchon M.; 1989 : Effects of two-dimensional topographies using the wavenumber boundary integral element method in P-SV cases . J. Acoust. Soc. Am., 85 , 2277-2283. Geli L., Bard P.-Y. and Jullien B.; 1988: The effect of topography on earthquakes ground motion: a review and new results . Bull. Seismol. Soc. Am., 78 , 42-63. Griffith D.W. and Bollinger G. A.; 1979: The effect of Appalachian mountain topography on seismic waves . Bull. Seismol. Soc. Am., 69 , 1081-1105. Hartzell S. H., Carver D. L. and King K. W.; 1994 : Initial investigation of site and topographic effects at Robinwood ridge. California. Bull. Seismol. Soc. Am., 84 , 1336-1349. Irikura K. and Kawanaka T.; 1980: Characteristics of microtremors on ground with discontinuous underground structure . Bull. Disaster Prev. Inst. Kyoto Univ., 30(3), 81–96. Jurkevics A.; 1988: Polarization analysis of three component array data. Bull. Seism. Soc. Am., 78 ,1725-1743. Kawase H. and Aki K.; 1990: Topography effect at the critical SV-wave incidence: possible explanation of damage pattern by the Whittier Narrows, California, earthquake of 1 October 1987 . Bull. Seismol. Soc. Am., 80 , 1-22. GNGTS 2014 S essione 2.2 259