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Jiri Zahradnik Charles University, Prague

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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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Presentation Transcript
slide1

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

Co-operation:

G-A. Tselentis, E. Sokos,

A. Serpetsidaki

V. Plicka, J. Jansky

sergoula mamousia university
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 university1
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 2001 serg black obs red synth
April 8, 2001SERGblack=obs.red=synth.

My “normal” job

is modeling, but

today I want to

discuss the data

reliability.

are our data accurate
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

vartholomio earthquake
Vartholomio earthquake
  • Dec.2, 2002
  • 04:58
  • M=5.4 (PATNET)
  • Mw=5.6 (MEDNET)
slide9
3T clipped

(2 mm/sec)

slide10
ZOOM

3T clipped

(2 mm/sec)

slide11
MAMO

clipped 3T viewed as non-clipped acceleration

(suggesting a method how to correct clipping)

slide12
MAMO

with the clipped part

without

noise natural and instrumental
Noise (natural and instrumental)

microseisms resolved by 3T, but not resolved by 5T

slide14
MAMO

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

vartholomio earthquake m 5 4 at serg 102 km1
Vartholomio earthquakeM 5.4at SERG (102 km)

temporary

GPS (digitizer)

problem

slide17
SERG

fit in EW as

good as in Z

(3T || 5T)

some HF noise ?

slide18
SERG

velocity

not clipped

velocity in SERG is lower than in MAMO,

but acceleration is SERG is higher

slide19
SERG

ZOOM

a significant HF ‘ringing’ of 3T

(not caused by clipping)

local event recorded at 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 km1
Local M 3.8 at SERG(13 km)

less problems on

the Z-comp. of 3T,

both in HF and LF

local event recorded at serg1
Local event recorded at SERG
  • Nov. 13, 2002
  • 21:55
  • M 3.0
  • SERG:

D=7.5 km

A=51o

slide28
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

slide29
occasionally,

the LF signal on 3T is “as bad” as on 5T !

slide30
LF

the LF signal

on Z-comp.

of 3T is OK

m 3 at serg 7 km
M 3 at SERG(7 km)

HF noise on horizontal

components of 3T

local event recorded at univ
Local event recorded at UNIV
  • Nov. 26, 2002
  • 12:13
  • M 3.5
  • UNIV:
  • D=13 km
  • A=209o
local event recorded at univ1
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
April 18, 2003 M 2.5at UNIV (5 km)

GPS recovered “itself”

april 18 2003 m 2 5 at univ 5 km1
April 18, 2003 M 2.5 at UNIV(5 km)

HF instrumental noise in 3T

LF instrumental noise in 5T

(complementary)

conclusion
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

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.

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