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The Rimini earthquake of 17th May 1916 (Italy): from historical data to seismic parameters. Marco Caciagli – Josep Batlló Istituto Nazionale di Geofisica.

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Presentation on theme: "The Rimini earthquake of 17th May 1916 (Italy): from historical data to seismic parameters. Marco Caciagli – Josep Batlló Istituto Nazionale di Geofisica."— Presentation transcript:

1 The Rimini earthquake of 17th May 1916 (Italy): from historical data to seismic parameters. Marco Caciagli – Josep Batlló Istituto Nazionale di Geofisica e Vulcanologia (Italy) European Seismological Commission ESC 2008, 31st General Assembly - Crete

2 1916 – Northern Adriatic Earthquakes Sequence 17 May – h: 12:50 Io = VIII ; Me = August – h: 07:06:14 Io = VIII ; Me=5.7 from May to December 1916 Main events included in the Euroseismos list (A priority)

3 Tectonic Setting (from Scrocca et al., 2007 modified)

4 Seismogenic Source Hypothesis 17 May 1916 Length (km) 8 ; Width (km) 5 Min Depth (km) 3 ; Max Depth (km) 5.5 Strike (deg) 132 Dip (deg) 30 Rake (deg) August 1916 Length (km) 8 ; Width (km) 5 Min Depth (km) 3 ; Max Depth (km) 5.5 Strike (deg) 132 Dip (deg) 30 Rake (deg) 90

5 1916 – Northern Adriatic Earthquakes Sequence (from Ferrari, 1986)

6 The Rimini earthquake of 17th May 1916 Me = 5.8 ; Io (MCS) = VIII Felt Localities 132 Felt Area Km 2 Damage Zone Km 2

7 The Rimini earthquake of 17th May 1916 Epicentral location…previous works

8 Epicentral Location 1916 BAAS (British Association for Advancement of Sciences) bulletin was strongly incomplete because of 1 st World War Reconstruction of the bulletin throughout each single Seismic Station bulletin available

9 Bulletins collected Station CodeStation Location 1) ABAAlger-Bouzareah (Algeria) 2) BIDBidston (England-UK) 3) BREBreslau - Wroclaw (Poland) 4) BUDBudapest (Hungary) 5) COICoimbra (Pourtugal) 6) CRTCartuja - Granada (Spain) 7) DBNDe Bildt (Holland) 8) EBREbro (Spain) 9) ESK Eskdalemuir (Scotland - UK) 10) FBRFabra (Spain) 11) GRAGraz - Steiermark (Austria) 12) KEW Kew (England-UK) 13) MARMarseilles (France) 14) MCIMonte Cassino (Italy) 15) MNCMoncalieri (Italy) 16) PARParis - Parc Saint Maur (France) 17) PMPPompei (Italy) 18) RDPRocca di Papa (Italy) 19) SFS San Fernando (Spain) 20) STRStrasbourg (France) 21) TAR Taranto (Italy) 22) TOLToledo (Spain) 23) TRE Trento (Italy) 24) UCCUccle (Belgium) 25) UPPUppsala (Sweden) 26) VIEVienna (Austria) 27) ZAGZagabria 28) ZURZurich (Switzerland) S waves from bulletinS waves from this work

10 Location Results Software used: Hypocenter (Lienert and Havskov, 1995) N E rms 5.1

11 Magnitudes Seismic Moment (Mo) and Moment Magnitude (Mw) Mo (k) = (4πρv 3 Ωo) / (G (r) R C) (Keilis-Borok, 1960) ρ = density ; v = wave velocity ; Ωo = low frequency level ; G (r) = Geometrical spreading ; R = radiation pattern correction ; C = free surface correction ; Mw = 2/3 log Mo - 6 (Hanks and Kanamori, 1979) Ms = log (A/T) log Δ° (Vanek et al., 1962) Surface-wave Magnitude Ms = log (A/G) log Δ° s (Abe, 1988) A = maximum trace amplitude (μm) ; T = period (sec) ; G = magnification of the Milne instruments Δ° = epicentral distance (degrees) ; s = station correction from Milne instrument

12 Selection of the available seismograms from Euroseismos website Download of seismograms from SISMOS Website, Collection of instrumental constant from station bulletins, station book and seismograms available from Euroseismos website, Euroseismos partners and other sources Digital Vectorization of selected seismograms Correction of pen curvature and arm inclination (skew), conversion of traces length (mm) into time (sec) Analysis of the waveforms to identify the P and S phases Spectral analysis in order to obtain the low-frequency level (Ω 0 ) Estimation of the seismic moment (M 0 ) and moment magnitude (M w ) Stages of work for the Mw estimation

13 List of seismograms used StzLat StzLong StzΔ°Δ (km)Instr.CompToVoh (damp) drum speed (mm/min) 1)ALM36,8525-2,459814, ,8Bosch-Omori 25N16,8614,50 14,63 2)ALM36,8525-2,459814, ,8Bosch-Omori 25E16,7213,80 14,63 3)DBN52,10175,17679, ,0GalitzinN253100,5 29 4)DBN52,10175,17679, ,0GalitzinE253100,5 28,97 5)EBR40,82060,493310, ,7Vertical PendelN2,61250,4 12 6)EBR40,82060,493310, ,7Mainka E7,81100,22 11,9 7)GTT51,54649,96427, ,1Wiechert 17000N1, ,43 61,38 8)GTT51,54649,96427, ,1Wiechert 1200E10,61600,24 10,03 9)GTT51,54649,96427, ,1WiechertZ3,62330,24 11,32 10)LEI51,33512,39177, ,3Wiechert 1000N82200,37 19,15 11)LEI51,33512,39177, ,3Wiechert 1000E8,52410,27 19,23 12)POT52,379313,06588, ,2Wiechert 1000N102800,4 10,72 13)POT52,379313,06588, ,2Wiechert 1000E63300,28 9,82 14)STR48,58367,76635, ,0Wiechert 1000N82000, )STR48,58367,76635, ,0Wiechert 1000E82000, )STR48,58367,76635, ,0Wiechert 1000Z52000, )TOL39,861-4,01713, ,6Wiechert 1000NE102000,46 15,03 18)TOL39,861-4,01713, ,6Wiechert 1000NW102000,46 15,1 19)UCC50,79834,35949, ,2Wiechert 1000N11,41560,5 14,95 20)UCC50,79834,35949, ,2Wiechert 1000E11,41650,5 14,93 21)UCC50,79834,35949, ,2Wiechert 1300Z4,81640, )UPP59,858317,626715, ,0Wiechert 1000N9,11880,36 12,35 23)UPP59,858317,626715, ,0Wiechert 1000E9,11870,38 12,435 24)ZAG45,816715,98302, ,1Wiechert 80NE10,12170,48 29,34 25)ZAG45,816715,98302, ,1Wiechert 80NW9,82170,5 29,64 Seismograms available by the Euroseismos project 40 seismograms 19 observatories

14 Seismograms elaboration After pen curvature and skew correction

15 The obtained ground displacement spectra were modelled using Brunes model (Brune, 1970, 1971) by fitting: U(ω) = Ωo / (1 + (ω / ω c ) γ ) Spectra analysis Ωo = 6,04E-05 fc = 0, Hz m x s

16 StationComponent Ω0 MoMw GTTN2,32E-041,01E+186,0 GTTE4,69E-058,16E+17 GTTZ7,18E-051,25E+18 POTN1,55E-052,51E+175,9 POTE4,56E-056,42E+17 UCCN6,05E-058,51E+176,0 UCCE5,80E-068,15E+16 UCCZ1,35E-041,90E+18 STRN6,95E-059,21E+176,2 STRE1,15E-041,53E+18 STRZ2,23E-052,96E+17 ZAGNE9,86E-069,18E+176,0 ZAGNW5,18E-064,82E+17 TOLNE1,03E-052,21E+175,9 TOLNW3,15E-056,77E+17 LEIN2,43E-054,28E+175,8 LEIE1,40E-052,47E+17 UPPN6,19E-051,48E+186,2 UPPE6,04E-051,44E+18 DBNN5,25E-056,98E+176,0 DBNE4,86E-056,45E+17 EBRN5,65E-041,36E+186,2 EBRE3,72E-054,85E+17 ALMN2,34E-055,66E+176,0 ALME2,34E-055,23E+17 Seismograms analysis results Mo = 1,14E+18 (Nm) Mw = 6.0 ± 0.1

17 Stz (milne)componentMs KEWE5,82 SFSE5,68 *BIDE5,97 TOLE5,87 StationComp.Ms (comp)Ms CRTN5,965,96 PARN5,915,88 PARE5,86 ABAE5,165,11 ABAN5,08 MARE5,815,89 MARN5,97 GRAE0,235,35 GRAN5,47 COIE6,106,14 COIN6,19 TOLNW5,635,58 TOLNE5,53 FBRE5,885,89 FBRN5,91 STRE6,696,59 STRN6,51 DBNE6,056,13 DBNN6,24 UCCE5,805,8 UCCZ5,80 UPPE5,845,84 VIEE5,926,00 VIEN6,08 Ms calculated from Milne instruments Surface-wave Magnitude Ms (Milne) = 5.8 ± 0.1 Ms = 5.8 ± 0.3 List of Ms calculated from each station

18 Conclusions and outlooks The epicentral location of the 17 May 1916 Rimini earthquake is clearly in the sea. The instrumental location error is quite large but the solution is robust. The comparison of the bulletins data with the original seismograms collected allowed us to reduce the misfits: projects like Euroseismos-type must be encouraged. For the first time Mw and Ms magnitudes has been instrumentally calculated. These results increase the databank of large earthquakes with calculated Mw. Future work We should invert the waveform for moment tensor determination and such procedure should be applied to other earthquakes of the Northern Adriatic Sequence.

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