1. Charles University Prague partner no. 16 (CUP) J. Zahradník, J. Janský, V. Plicka

2. Deliverables 12Data base for selected stations of CUP (WP1) Plan: attention to “classical” issues (location, focal mechanisms, strong motions) as well as various transients possibly related to strain

3. Present status: 8 CUP instruments jointly operated with UPATRAS at 4 sites 2 stand-alone (SERG, MAMO) 2 satellite (LOUT, PYLO) each one with CMG-3T and 5T (weak & strong)

4. SERG (Sergoula)

5. MAMO (Mamousia)

6. Deliverables 31 new vault for re-installation of CUP BB stations (WP1; UPATRA) Plan: SERG, 3-4 m deep excavation, pillar at the bottom, thermal insulation.

7. CMG-3T: 9 days in June, velocity no vault amplitude of the order of 10 -5 m/s

9. the same site after adding simple polystirin insulation improvement factor of 2

10. before and after thermal variation obvious, better insulation needed

11. Vartholomio earthquake Dec.2, 2002 04:58 M=5.4 (PATNET)

12. BB: MAMO not equal SERG MAMO, D=94 km, A=66 o SERG, D=102 km, A=50 o M5.4 Vartholomio December 2, 2002

13. MAMO versus SERG MAMO, D=94 km, A=66 o SERG, D=102 km, A=50 o

14. at f < 0.1 we get rid of site effects MAMO SERG 5T as good as 3T for M5.4

15. Both CMG-3T and CMG-5T are needed (even for small local events): Example: M3.8, 13 km (SERG)

16. Local event recorded at SERG Dec.10, 2002 16:47 M 3.8 SERG: D=13 km A=84 o

17. 3T problem at HF 5T problem at LF 3T almost clipped

18. Local M3.8 event: 3T needed to get f < 0.1 Hz M 3.8 recorded at D=13 km

20. Can we also contribute to studies of slow strain events ? Example: December 3, 2002 (suggested by Pascal B.) lower thermal variation in winter velocity record supplemented by “mass channel” (integrated velocity output)

21. CMG-3T; 9 days “mass channel”, SERG

22. CMG-3T 3 days “mass channel”: an anomaly superimposed on the thermal variation EW NS

23. Zooming anomaly on EW (1 day)

24. ... and the corresponding velocity

25. increased noise ? anomaly M3.5 earthquake

26. the anomaly consists of eqs. and 4-5 minute long pulses, 10 -5 m/s 4 10 -6 m/s 10 -5 m/s CMG3-T: 1 day (Dec. 3, 2002)

27. Just these 4-5 minute long pulses constitute the anomaly of the mass channel.

28. M3.5 Dec. 3 23:42 and what happens during eq. ?

29. Mass channel

30. Velocity: signature of a sudden local tilt M3.5 10-20 km

31. Modeling a similar event Corinth Gulf M3, distance 10km

32. Normal instrument response of CMG-3T to abnormal input: ACCELEROGRAPH 100-SEC VELOCIGRAPH input output input output

33. Modeling the CMG-3T response we arrive at the horizontal acceleration step of 6.10 -6 m/s 2 tilt step 6.10 -7

34. The collocated CMG-5T accelerograph has the tilt pulse below its instrumental noise ! Anyway, CMG-5T is also needed for other purposes: Example: M3.8, 13 km (SERG)

36. Note the undisturbed vertical component, typical for the tilt. low pass f < 1 Hz: data model response

37. How about STS-2 (120-sec) ? STS-2, temporarily operated at the same station SER recorded some 300 local events, and 3 of them have had an analogous disturbance

38. Dec. 3 23:42

39. Mass channel

40. 5 min ! Following the sudden tilt (< 100 sec), accompanying the earthquake, there is a slow “strain recovery” but its amplitude is 10-30 smaller than slow pulses accompanying the preceding burst of smaller eqs.

41. P. Bernard: The strain pulse of Dec. 3, 2002 is below the CMG-3T noise strain 10 -8, 10 km, 500 s... 10 -7 m/s noise > 10 -6 m/s not too far !

42. Faster strain change can be seen easily right now “faster” ( < < 100 sec) = “sudden” for CMG-3T sudden strain increase = accel. step

43. Database (V. Plicka) http:/seis30.karlov.mff.cuni.cz

44. regional local transients

47. Deliverables 16New software for source-parameter inversion (WP1) Innovation: LF local waveforms (f < 0.1 Hz) moment tensor, uncertainty of non-DC, multiplicity in space and time synthetic and/or empirical Green fctn.

48. Zahradník, J., Janský, J., Sokos, E., Serpetsidaki, A., Lyon-Caen, H., and Papadimitriou, P. : Modeling the M L 4.7 mainshock of the February-July 2001 earthquake sequence in Aegion, Greece. (J. of Seismology, 2004)

49. Zahradník, J., Janský, J., Sokos, E., Serpetsidaki, A., Lyon-Caen, H., and Papadimitriou, P. : Modeling the M L 4.7 mainshock of the February-July 2001 earthquake sequence in Aegion, Greece. (J. of Seismology, 2004) amplitude-spectra inversion 0.1 - 0.2 Hz

50. Zahradník, J., Janský, J., Sokos, E., Serpetsidaki, A., Lyon-Caen, H., and Papadimitriou, P. : Modeling the M L 4.7 mainshock of the February-July 2001 earthquake sequence in Aegion, Greece. (J. of Seismology, 2004) inversion of the amplitude spectra 0.1 - 0.2 Hz

51. Iterative deconvolution of regional waveforms Zahradník, J., Serpetsidaki, A., Sokos, E., Tselentis, G-A.: Iterative deconvolution of regional waveforms and double-event interpretation of the 2003 Lefkada earthquake, Greece (Bull. Seism. Soc. Am., in press)

52. M6 Lefkada earthquake Aug.14, 2003 5 BB stations epic.distance <140 km

53. Method moment-tensor inversion (minimization of the L2 waveform misfit by the weighted least-square method) optimization of the source position and time (maximization of the correlation by the space-time grid search) a single point source for f < 0.1 Hz, and multiple point sources for f < 0.3 Hz

54. Final solution: 2 main subevents, 40 km and 14 sec apart explaining the two aftershock clusters

55. Two sources explain the Lefkada earthquake better than one black: one subevent red: two subevents SERG

56. Matching data by synthetics (4 subevents) and checking stability stability check: repeatedly removing 1 station

57. Checking stability of subevents (repeatedly removing one station) mom1=mom2=0.5e18 Nmmom3=mom4=0.2e18 Nm sub 4 is lesscertain

58. DC or non-DC ? Note that the two largest subevents have a slightly different focal mechanism. Their tensorial sum can mimic an apparently non-shear event. We have no indication about a true departure from 100% DC.

59. PROBLEMATIC NON-SHEAR MECHANISM OF MODERATE EARTHQUAKES IN WESTERN GREECE (ESC, Potsdam 2004) J. Zahradník, E. Sokos

60. Vartholomio (near Zakynthos) Dec. 2, 2002 ETH-SED: Mw=5.7 DC%=55 ! (HRV: DC%=58, Mednet: DC%=44) Zakynthos

61. 6 NOA stations, f=0.05 to 0.1 Hz weights proportional to 1/A were applied blue: data black: synthetics for crustal model of Haslinger et al. (1999)

62. 100% DC matches data also well (only 0.05 worse) we cannot see the difference

63. Going into large details: Optimum correlation is not compatible with 100% DC trial source position trial time shift

64. Repeating inversion with station removals: uncertainty assessment green: DC-percentage (with red ‘error bars’) blue: correlation

65. Very stable strike-dip-rake but highly unstable DC percentage DC%: 72 to 97 % cf. 55% (ETH)

66. Fixing the opt. source position and increasing frequency (f < 0.3 Hz): 3 subevents 2-sec time delay between sub 1 and 2; sub 3 is unstable

67. Subevents 1 and 2: similar strike and dip, but different rake Consider sub 1 and 2 as 100% DC (but unequal !), and sum up their moment tensors: Result: sub 1+ 2 provides DC% 77 to 93%, analogous to the previous single-source study. Multiplicity seems to explain the non-DC mechanism.

68. The new trial fault plane is given by the patch (point 3) and the known strike (303 o ) old epicenter patch 5 trial source positions at each depth (16,17, and 18 km) the old epicenter now appears slightly off the plane (location error)

69. the subevent time separation is stable (2 + 2 sec), and the focal mechanism as well, incl. sub 3 2 + 2 sec

70. The optimized “fault plane” stabilized the solution a lot. Sub 1,2,3 are not separated more than ~2 km from each other, but the delay is 2+2 seconds. = small distance, large delay. Rupture propag. with arrest ? A multiple event ! trial vertical plane 8 x 2 km removed station RLS VLS ITM EVR JAN KEK

71. RLS station: unfiltered data velocitydisplacement data model both NS, EW explained by an accel. step 6. 10 -4 m/s 2 tilt 6. 10 -3

72. Restoration of normal seismic motion: = data minus model response green = blue - red data model response

73. Validation of the restored record through forward source modeling normalized displacement, band passed 10-20 sec before removal after removal !! Only now the record can be used to study seismic source !! restored data synth. data

74. Near-fault seismic displacement has a static offset. Calculate it for nearby points, and get the strain and tilt. Example: RLS station (40 km from the M5 Vartholomio earthquake) the synthetics yield: permanent tilt = 2. 10 -8 acc. step = 2. 10 -7 m/s 2 but we observed the accel. step 3 orders of magnitude larger... SYNTHETIC TEST

76. Deliverables 95New software for near-real time seismic alarms (WP8) PEXT: perturbation and extrapolation finite-extent fault, composite source modeling deterministic envelopes and accel. spectral level, stochastic HF phase; perturbed HF radiation pattern

77. Colfiorito Mw 6.0 benchmark (M. Cocco)

78. forward station

79. ... and backward station

80. “Moderate” directivity GTAD CTOR

81. Macroseismic observations: Alonnisos motion << Skyros motion (V. Karakostas)

82. Modeling strong motion based on weak-motion source model rupture propagation towards SE and the corresponding directivity effect

83. Athens 1999 - PGA modeling Shake map up to 20 Hz in a few minutes on a PC

84. Tuning maximum slip velocity against the attenuation relation

85. Athens - synth. versus real records

86. ... another station

87. Charles University Prague (CUP) summary of the tasks 12Data base for selected stations of CUP (earthquakes + transients) 16 New software for source-parameter inversion (moment tensor, multiplicity) 95New software for near-real time seismic alarms (directivity, fast computations) http:/seis30.karlov.mff.cuni.cz