GNGTS 2014 - Atti del 33° Convegno Nazionale

Rayleigh waves are represented, for all the sites but separately for the two techniques. Most ESAC profiles showa sharp velocity decrease in the first fewmeterswhile velocity progressively increases with depth (Fig. 2, top). Due to the slightly different approach for data inversion, the specific behavior at shallow depth is not observed in the Re.Mi. velocity profiles (Fig. 2, bottom). Pseudo-2D section. The trace of the profile runs in a SSW-NNE direction from near Cento to the east of Bondeno. The investigated sites laying out of the profile trace, because of topographic or access difficulties, have been perpendicularly projected and their distance from the trace ranges between 60 and 900 m. Although 1D profiles have been locally reconstructed at greater depths, the interpretation of the section has been attempted to a depth of 150 m b.s.l. (considering that the altitude of the investigated sites ranges between 7 and 15 m a.s.l.). In order to obtain the pseudo-2D velocity section, all 1D projected velocity profiles have been interpolated with different techniques all showing some major features. Due to the similarity of the interpolations, in Fig. 3 only the interpolation obtained by applying the local polynomial method is illustrated and discussed. If we reasonably assume that the overall pattern of the shear wave velocity is determined by lithological variations, both lateral and vertical ones, especially in terms of different sedimentation rate ( i.e. different ages at comparable depths), the pseudo-2D section represented in Fig. 3 allows to infer the occurrence of buried anticlinal structures in correspondence with the higher velocity gradients associated with a (more) ‘condensed’ stratigraphy. Conversely, where velocity gradients are lower, the thickness of the coeval sedimentary units is greater ( i.e. synclinal structures). If we compare our results with available geological profiles crossing the same investigated area (Fig. 1), it is possible to observe a good agreement with the occurrence of some major Tab. 1 - Coordinates of the investigated sites. site label latitude longitude latitude longitude (UTM32N, km) (UTM32N, km) (°N) (°E) 1 Re.Mi._9_R 4955321.342 680148.539 44°43’36.65” 11°16’25.94” 2 ESAC006 4957368.578 681854.073 44°44’50.05” 11°18’09.39” 3 Re.Mi._8_R/L 4959077.820 682045.420 44°45’36.57” 11°17’56.93” 4 ESAC005 4959281.085 683264.939 44°45’45.21” 11°18’55.79” 5 ESAC004 4960660.598 684315.250 44°46’29.00” 11°19’45.62” 6 ESAC003 4961671.719 684777.700 44°47’1.74” 11°20’7.84” 7 Re.Mi._10_R 4962853.122 685783.316 44°47’35.36” 11°20’51.77” 8 ESAC002 4963654.769 687042.923 44°48’3.65” 11°21’53.28” 9 ESAC001 4965371.322 686964.542 44°48’59.74” 11°21’51.88” 10 ESAC010 4966249.194 687756.194 44°49’27.19” 11°22’29.19” 11 Re.Mi._6_R 4967058.276 687402.990 44°49’50.00” 11°22’11.00” 12 ESAC007 4967338.695 688579.199 44°50’1.53” 11°23’7.48” 13 BN_14_R/L 4967883.042 688148.009 44°50’16.00’’ 11°22’46.00’’ 14 ESAC008 4969384.450 690044.932 44°51’5.80” 11°24’18.89” 15 ESAC011 4971312.633 691557.693 44°52’7.36” 11°25’28.74” 16 BN_04 4972431.908 691392.196 44°52’40.18” 11°25’19.81” 17 ESAC012 4972707.823 692788.281 44°52’50.81” 11°26’27.14” 18 ESAC009 4974040.307 694034.546 44°53’32.68” 11°27’25.94” 19 BN_11_R/L 4974705.786 694270.004 44°53’51.00’’ 11°27’34.00” 20 ESAC013 4975796.051 694379.424 44°54’29.48” 11°27’43.13” 120 GNGTS 2014 S essione 1.2