Portable Broadband Seismic Stations -
Checking Data Quality
Cairo, EgyptNovember, 2009
Noel BarstowBruce BeaudoinMarcos Alvarez
Checking Data QualityKeep good records of everything
> Before going to the fieldTest all Instrumentation and Cables
> In the fieldInstall Station and Check: Power, Timing, Sensor Orientation, Signal
Visit stand-alone stations frequently to: Download Data and Review Station Status and Metadata on site
> In the labArchive, Analyze, and Document Data
Hardware Maintenance and QC: Dataloggers
Function test all Dataloggers prior to shipment:Bit weight, oscillator drift, data time stamps
Keep maintenance records in an electronic databaseTest and upgrade firmware when necessary
PASSCAL’s Hardware Maintenance: Seismometers
Feedback seismometers are Pier-Tested for 4-7 Days and compared to a Reference Sensor:- Amplitude and Phase- Polarity- Spectral Content- Noise Characteristics
Electronic Calibrations:- Corner Period- Damping
Do the signals look the same?
close up of verticals
overlay surface wave
Nightly Plots of Pier Tests
Electronic Step Calibration
White Noise Calibrations
Input White Noise
Pha
se
Am
plitu
deSensor Output
Sensitivity
Pier Data Comparing Sensor Noise of Different Sensor Types
Ve
rtic
al C
om
pon
en
ts
Streckeisen STS-2
€
X = − 2 /3( ) U + 1/6( ) V + 1/6( ) W
Y = 1/2( ) V − 1/2( ) W
Z = 1/3( ) U + 1/3( ) V + 1/3( ) W
STS-2 Element Contribution to Signal
East
North
Vertical
STS-2 Element V problem
Z
N
E Noisy Sensor
Z
N
E
Triaxial SystemsR
efer
ence
Unfiltered Earthquake Filtered 10 -30 sec period
Z
N
E
Z
N
E
Tes
t S
enso
r:
Drif
t &
DC
off
set
Orthogonal elements2 Horizontal1 Vertical
Guralp CMG-3T
Replace Bent 3T Pivot
Comparing Reference and Problem Sensor
Before
After
Time Scale = 3 hours
Eas
t /
Wes
t C
ompo
nent
Sudden Noise on Guralp 3T Vertical Component
Noise begins
Noisy Spectra
Days:
1
2
3
4
Ver
tical
Dat
a
Spe
ctra
Locking and Unlocking the 3T provides a temporary fix
Amplitude change at DC offset
Time = 8 Days
N/S
E/W
Z
Amplitude Problem: Loss of Differential Output
Das, Sensor, or interconnecting Cables could be the cause
•PASSCAL develops and maintains software to extract data from the dataloggers, perform in-field quality checks, and manipulate the waveforms into archive formats.
•http://www.passcal.nmt.edu•ftp.passcal.nmt.edu
Data QC & Software
Data Archiving Support PASSCAL acts as an intermediary between
PASSCAL Investigators and the DMC
• Check completeness of data submitted to PASSCAL
• Help evaluate or fix timing
• Verify SEED Format
• Ensure agreement between data and metadata
• Check completeness of data submitted to DMC
• PASSCAL provides email and phone support for our users before, during, and after experiments to analyze specific problems.
• PASSCAL staff members are available for the initial testing and installation phase of field campaigns.
• Typically there are over 500 broadband and short-period PASSCAL stations deployed at any given time.
• Contact us: [email protected]
Troubleshooting
After the power point presentation
Live demonstration oflogpeek - plotting of RT130 station log
messagespql - PASSCAL Quick Look - to view
waveforms, fast fourier spectrum, split view, etc.
pql will read mini-seed, sac, and segy formats
Review Station’s Status
Firmware
Volts
GPS
Timing
Time Scale = 1 WEEK
‘logpeek’Plot of StationLog MessagesFromRT130 DAS
