Iolanda Gabriela CRAIFALEANU Technical University of Civil Engineering Bucharest, Romania & National R&D Institute “URBAN INCERC”, INCERC Bucharest Branch i.craifaleanu@gmail.com, iolanda.craifaleanu@utcb.ro PPT available at: Iolanda Gabriela CRAIFALEANU AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES Radiation directivity significantly differentiated between the 4 analyzed earthquakes Strong Vrancea events Seismic events: January 1st, 1900 – December 31st, 2008. Data according to ROMPLUS Catalogue (INFP, 2009) Radiation directivity 04.03. 1977 NE SW Difficulties in identifying the depth of the base rock for a large part of the area affected by Vrancea earthquakes 30.08. 1986 NE SW 30.05. 1990 N S 31.05. 1990 NW SE Simplified classification: 2 basic types of sites, according to the event to event variability of the frequency content variable frequency content determinant influence of the focal mechanism & radiation / long distance attenuation stable frequency content determinant influence of local soil conditions PPT available at: Iolanda Gabriela CRAIFALEANU AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES Database of 300+ ground motions recorded during 4 strong earthquakes (Mw>6) generated by the Vrancea seismogenic zone since 1977 Ground motion database: 313 records 122 Vrancea Earthquakes Comparative analysis of 11 analytical estimators of the frequency content Results correlated with information provided by 4 spectral bandwidth measures 101 87 85 70 61 31 3 2 37 26 1 March 4, 1977 Aug. 30, 1986 May 30, 1990 May 31,1990 March 4, 1977 Aug. 30, 1986 May 30, 1990 May 31, 1990 Mw=7.4 Mw=7.1 Mw=6.9 Mw=6.4 h=94 km h=131 km h=91 km h=87 km PPT available at: Iolanda Gabriela CRAIFALEANU AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES TgSA predominant period T1(PSD) period for the highest PSD amplitude peak Tcen central period % * & , Tmean mean period % * 1 , ω % ( ) ' ) ( & & Tms mean square period (9 22:   Tms = ∑ Ci2  1  ∑ Ci2   fi  i i  for 0.25Hz ≤ fi ≤ 20Hz '( ( 0 6 & acceleration spectrum TgSV predominant period velocity spectrum TgSEI predominant period input energy spectrum Tmean* mean* modified mean period Tcen* cen* modified central period &) ( " % ( 00 % * T4.3 characteristic period empirical () 66 , T4.3 = 4.3 , 0 9% 0 ( 22 TC characteristic period, alternate % ) ) ,7 6 & & & , ) % 2:3 PGV PGA ( 6 # $ % & & ' (& % % % ) ( * + % ( + $-! ./0 $-! &) ! 223 shape factor, q & 1 234 ε parameter 5 ' 6( 7 6 ! ξ parameter 8 modified shape factor, q*, # $ 66 !" 2$4 PPT available at: Iolanda Gabriela CRAIFALEANU AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES Good and remarkably stable correlations between: Tms (Rathje et al., 1998) and TC (Lungu et al., 1997) Tmean (=1/mean freq. of power spectrum) T4.3 (Heidebrecht, 1987) By using the y=a— x dependency, both R2 and a coefficients show remarkably low event to event variability Simple Simple empirical empirical relationships relationships between between the /type theTT/type parameters parameters Tms T1(PSD) Tmean Tcen TgSA TgSV Tms 1 T1(PSD) 0.531 Tmean 0.763 Tcen 0.570 TgSA 0.441 TgSV 0.285 TgSEI 0.417 TC 0.831 Tmean* 0.330 Tcen* 0.235 T4.3 0.759 y=a y=a— x+b horizontal components TgSEI TC Tmean* Tcen* T4.3 q q* ε ξ 0.531 0.763 0.570 0.441 0.285 0.417 0.831 0.330 0.235 0.759 0.515 0.574 0.445 0.551 1 0.384 0.261 0.227 0.189 0.358 0.468 0.242 0.182 0.378 0.324 0.375 0.161 0.201 0.921 0.543 0.127 0.204 0.512 0.111 0.066 0.559 0.272 0.267 0.481 0.588 0.384 1 0.261 0.921 0.227 0.543 0.443 0.189 0.127 0.071 0.030 0.358 0.204 0.126 0.064 0.417 0.468 0.512 0.341 0.276 0.366 0.426 0.242 0.111 0.048 0.023 0.627 0.403 0.401 0.182 0.066 0.023 0.007 0.574 0.338 0.290 0.975 1 0.378 0.559 0.410 0.307 0.266 0.318 0.715 0.356 0.276 1 good y= a— xx y=a— R2 Tms/TC a R2 Tms/Tmean a R2 Tms /T4.3 a 0.443 0.071 0.126 0.341 0.048 0.023 0.410 0.098 0.149 0.420 0.491 0.030 0.064 0.276 0.023 0.007 0.307 0.196 0.108 0.356 0.435 1 1 0.417 0.366 0.627 0.574 0.266 0.253 0.565 0.127 0.133 0.426 0.403 0.338 0.318 0.258 0.474 0.111 0.127 1 1 0.401 0.290 0.715 0.442 0.673 0.274 0.371 1 0.975 0.356 0.229 0.769 0.053 0.072 intermediate 0.276 0.160 0.626 0.028 0.040 0.379 0.519 0.310 0.372 1 weak correlation 30.08. 1986 30.05. 1990 31.05. 1990 0.8122 0.8006 0.7238 1.5409 0.7146 1.2008 0.8143 0.7954 0.7723 1.5304 0.6745 1.1049 0.2084 0.8083 0.6978 1.4562 0.6137 1.1705 All records, incl. 04.03.1977 0.7954 0.8017 0.7619 1.5328 0.7216 1.1508 Iolanda Gabriela CRAIFALEANU PPT available at: AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES T1(PSD) period for the highest PSD amplitude peak Stations in the NE & SE : relatively small variability of T1(PSD) values with the event suggests prevalent influence of local site conditions on freq. content Other stations : large T1(PSD) values (& narrowband motions) for one (two) events & much smaller values for the other event(s) suggests prevalent influence of focal mechanism & radiation for these stations Same observations for Tms Iolanda Gabriela CRAIFALEANU PPT available at: AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES T1(PSD) period for the highest PSD amplitude peak Large values of T1(PSD) for the 1986 earthquake (& narrowband motions), for one or both horizontal components of all Bucharest records Opposite situation for the 1990 earthquakes ; ) 8 $ 22 # Probable explanation the different characteristics (directivity of radiation / attenuation) of the analyzed earthquakes Iolanda Gabriela CRAIFALEANU PPT available at: AN ASSESSMENT OF THE RELEVANCE OF PARAMETERS USED FOR GROUND MOTION FREQUENCY CONTENT CHARACTERIZATION WITH APPLICATION TO VRANCEA SUBCRUSTAL EARTHQUAKES Good and remarkably stable correlations found between the mean square period, Tms (Rathje et al., 1998) and the characteristic period, TC (Lungu et al., 1997) the mean period of the power spectrum, Tmean the characteristic period based on peak ground motion values, T4.3 (Heidebrecht, 1987) simple empirical relationships between the above parameters Interevent (event to event) variability of T type parameters and factors influencing the frequency content of the ground motion: low variability suggests prevalent influence of local site conditions high variability suggests prevalent influence of ground motion of focal mechanism & radiation, given the differences between the characteristics of the analyzed earthquakes