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NEAREST WP3 meetingBerlin 8tth October 2008, Technische Fachhochschule Berlin
Seismic data from GEOSTAR
Stephen Monna and Francesco FrugoniI.N.G.V. - Rome
Presentation overview
Data statistics
Signal qualityDisturbancesPossibility to “cure” disturbances
Data examples
Conclusions
GURALP CMG-40T 3 component broadband seismometer (30 s-50 Hz)
GURALP CMG-5T 3 component broadband accelerometer, strong motion (DC-100 Hz)
OAS E-2PD- Hydrophone 0- 5KHz
100 Hz sampling, 7 channels 24 bit + 3 mass channels 16 bit
GURALP DM-24 Digitizer, 7 channels at 24 bit + 3 auxiliary OBS mass channels at 16 bit
synchronization from SERCEL rubidium clock- input in GPS DM-24 channel
MCU restarted day 53 (17 October 2007)
Number of bytes recorded/day for OBS, ACC, HYD
For OBS: 2.22*10^4 over 2.34*10^4 Mbytes = 95 % of expected bytes recorded
21 August 2007- Port of Faro, Portugal
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
Time 200 s
Recording 7 channels before deployment
First recording period after deployment 7 channels25 August 2007
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
Time 200 sHydrophone breakdown
145 s period disturbance
Detail- hydrophone breakdown, note the corresponding step on ACC
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
Time 10 s
25 August 2007
Hydrophone- comb-style waveform starts25 August 2007
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
Time 100 s
Example 1 hour recording for all 7 channels
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
Time 500 s
06 March 2008
06 March 2008
OBS-E
OBS-Z
OBS-N
ACC-Z
ACC-N
ACC-E
HYD
Zoom on 145 s period disturbance
Time 20 s
This signal form strongly suggests leveling of the sensors is going on
Effect of simple cleaning procedure, teleseismic event Mw6.9 N-mid atlantic ridge
Onset first P-arrival 1 Hz, at 9:45:40 (no drift correction)
Arrival at Portuguese land station PFVI (100 km from GEOSTAR ), 9:45:477 s difference is in agreement with P traveltime tables for shallow eventsClock drift for the whole mission is 184 ms in 359 days ---> ~ 0.51 ms/day
time10 s
before
after
time 5 s
Signal cleaning example for a very local event (not present on local seismic bulletins)
before
after
Onset P arrival
Bandpassed 4-20 Hz 4 poles, butterworth