1. Three BB and SM seismic stations in the Corinth Gulf jointly operated by the universities in Prague and Patras Jiri Zahradnik Charles University, Prague

2. Co-operation: G-A. Tselentis, E. Sokos, A. Serpetsidaki V. Plicka, J. Jansky

3. Sergoula, Mamousia, University CMG 3T BB vel CMG 5T SM acc DM24 + SAM 20 Hz continuous 100 Hz triggered stand-alone 3-5 months

4. Sergoula, Mamousia, University CMG 3T BB vel CMG 5T SM acc DM24 + SAM 20 Hz continuous 100 Hz triggered stand-alone 3-5 months

5. April 8, 2001 SERG black=obs. red=synth. My “normal” job is modeling, but today I want to discuss the data reliability.

6. Are our data accurate ? Compare the instrumentally corrected records, sampling 100 Hz (5T accel. and the differentiated 3T) Demonstrate complications velocity acceleration Zeros and poles from factory calibration tests

7. Vartholomio earthquake Dec.2, 2002 04:58 M=5.4 (PATNET) Mw=5.6 (MEDNET)

8. Vartholomio Dec. 2, 2002 M 5.4 at MAMO (94 km)

9. 3T clipped (2 mm/sec)

10. 3T clipped (2 mm/sec) ZOOM

11. MAMO clipped 3T viewed as non-clipped acceleration (suggesting a method how to correct clipping)

12. MAMO with the clipped part without

13. Noise (natural and instrumental) microseisms resolved by 3T, but not resolved by 5T

14. MAMO Minimum frequency available from the 5T accelerograph (M 5.4; 94 km)

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

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

17. Vartholomio earthquake M 5.4 at SERG (102 km)

18. temporary GPS (digitizer) problem

19. SERG fit in EW as good as in Z (3T || 5T) some HF noise ?

20. SERG velocity not clipped velocity in SERG is lower than in MAMO, but acceleration is SERG is higher

21. SERG a significant HF ‘ringing’ of 3T (not caused by clipping) ZOOM

22. SERG

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

25. Local M 3.8 at SERG (13 km)

26. less problems on the Z-comp. of 3T, both in HF and LF

27. Too noisy LF signal on 5T even at f ~ 0.1 Hz M 3.8 recorded at D=13 km

29. Local event recorded at SERG Nov. 13, 2002 21:55 M 3.0 SERG: D=7.5 km A=51 o

30. SERG November 13, 2002; at 21:55; M 3 SERG: D=7.5 km, A=51 o NS-comp. of 3T velocityEW-comp. of 3T velocity a rare disturbance (signal-generated)

31. occasionally, the LF signal on 3T is “as bad” as on 5T !

32. LF the LF signal on Z-comp. of 3T is OK

33. M 3 at SERG (7 km) HF noise on horizontal components of 3T

34. Local event recorded at UNIV Nov. 26, 2002 12:13 M 3.5 UNIV: D=13 km A=209 o

35. Nov. 26, 2002 M 3.5 at UNIV (13 km)

36. GPS problem

37. Local event recorded at UNIV Apr. 18, 2003 12:49 M 2.5 UNIV: D=5 km A=126 o

38. April 18, 2003 M 2.5 at UNIV (5 km) GPS recovered “itself”

39. April 18, 2003 M 2.5 at UNIV (5 km) HF instrumental noise in 3T LF instrumental noise in 5T (complementary)

40. Conclusion joint deployment of 3T BB and 5T SM revealed problems of both instruments HF noise peak (30 Hz) on horiz. comp. of 3T white accel. noise of 5T occasional disturbances on horiz. 3T (tilt ?) temporary timing (GPS, digitizer) problems

41. Instrumentally “corrected” records are rarely correct to every detail. Joint deployment of the 3T (BB) and 5T (SM) helps to reveal problems, and the instruments complement each other.

42. All data available from http://seis30.karlov.mff.cuni.cz Thank you !