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Jiri Zahradnik Charles University, Prague

Three BB and SM seismic stations in the Corinth Gulf jointly operated by the universities in Prague and Patras. Jiri Zahradnik Charles University, Prague. Co-operation:. G-A. Tselentis, E. Sokos, A. Serpetsidaki V. Plicka, J. Jansky. Sergoula, Mamousia, University. CMG 3T BB vel

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Jiri Zahradnik Charles University, Prague

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  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, 2001SERGblack=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 Zeros and poles from factory calibration tests acceleration velocity

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

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

  9. 3T clipped (2 mm/sec)

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

  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. Vartholomio earthquakeM 5.4 at SERG (102 km)

  16. Vartholomio earthquakeM 5.4at SERG (102 km) temporary GPS (digitizer) problem

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

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

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

  20. SERG

  21. SERG

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

  23. Local M 3.8 at SERG(13 km)

  24. Local M 3.8 at SERG(13 km) less problems on the Z-comp. of 3T, both in HF and LF

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

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

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

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

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

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

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

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

  33. Nov. 26, 2002M 3.5 at UNIV(13 km) GPS problem

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

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

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

  37. 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

  38. 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.

  39. All data available fromhttp://seis30.karlov.mff.cuni.cz Thank you !

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