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
• CMG 5T SM acc
• DM24 + SAM
• 20 Hz continuous
• 100 Hz triggered
• stand-alone
• 3-5 months
Sergoula, Mamousia, University
• CMG 3T BB vel
• CMG 5T SM acc
• DM24 + SAM
• 20 Hz continuous
• 100 Hz triggered
• stand-alone
• 3-5 months
April 8, 2001SERG
black=obs.red=synth.
My “normal” jobis modeling, buttoday I want to discuss the datareliability.
Are our data accurate ?
• Compare the instrumentally corrected records, sampling 100 Hz (5T accel. and the differentiated 3T)
• Demonstrate complications
velocityacceleration
Zeros and poles fromfactory calibration tests
Vartholomio earthquake
• Dec.2, 2002
• 04:58
• M=5.4 (PATNET)
• Mw=5.6 (MEDNET)
VartholomioDec. 2, 2002
M 5.4at MAMO
(94 km)
3T clipped(2 mm/sec)
3T clipped(2 mm/sec)
ZOOM
MAMO
clipped 3T viewed as non-clipped acceleration(suggesting a method how to correct clipping)
MAMO
with the clipped part
without
Noise (natural and instrumental)
microseisms resolved by 3T, but not resolved by 5T
MAMO
Minimum frequency available from the 5T accelerograph (M 5.4; 94 km)
Vartholomio earthquakeM 5.4
at SERG (102 km)
Vartholomio earthquakeM 5.4
at SERG (102 km)
temporaryGPS (digitizer)problem
SERG
fit in EW asgood as in Z(3T || 5T)
some HF noise ?
SERG
velocitynot clipped
velocity in SERG is lower than in MAMO,but acceleration is SERG is higher
SERG
a significant HF ‘ringing’ of 3T(not caused by clipping)
ZOOM
SERG
SERG
Local event recorded at SERG
• Dec.10, 2002
• 16:47
• M 3.8
• SERG:
D=13 km
A=84o
Local M 3.8 at SERG(13 km)
Local M 3.8 at SERG
(13 km)
less problems onthe Z-comp. of 3T,both in HF and LF
Too noisy LF signal on 5T even at f ~ 0.1 Hz
M 3.8 recorded at D=13 km
Local event recorded at SERG
• Nov. 13, 2002
• 21:55
• M 3.0
• SERG:
D=7.5 km
A=51o
SERGNovember 13, 2002; at 21:55; M 3
SERG: D=7.5 km, A=51o
NS-comp. of 3T velocity EW-comp. of 3T velocity
a rare disturbance(signal-generated)
occasionally,the LF signal on 3T is “as bad” as on 5T !
LF
the LF signal on Z-comp. of 3T is OK
M 3 at SERG
(7 km)
HF noise on horizontalcomponents of 3T
Local event recorded at UNIV
• Nov. 26, 2002
• 12:13
• M 3.5
• UNIV:
• D=13 km
• A=209o
Nov. 26, 2002M 3.5
at UNIV(13 km)
Nov. 26, 2002M 3.5
at UNIV(13 km)
GPS problem
Local event recorded at UNIV
• Apr. 18, 2003
• 12:49
• M 2.5
• UNIV:
D=5 km
A=126o
April 18, 2003 M 2.5
at UNIV (5 km)
GPS recovered “itself”
April 18, 2003 M 2.5
at UNIV(5 km)
HF instrumental noise in 3TLF instrumental noise in 5T(complementary)
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
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.
All data available fromhttp://seis30.karlov.mff.cuni.cz
Thank you !
Top Related