Seismic Network Operations

IU JOHN

Johnston Island, USA

IU JOHN commences operations on: 1998,205

Country Flag
Host: US Fish and Wildlife Service
Latitude: 16.733
Longitude: -169.529
Elevation: 2
Datalogger: Q330
Broadband: STS-2_Standard-gain
Accelerometer: FBA_ES-T_EpiSensor_Accelerometer
Telemetry Status at the NEIC: Last Data In Less Than 10 Minutes
Station Photo Station Photo Station Photo 

Site Description: Solar powered site in the middle of a 1/2 mile by 2 mile Pacific atoll.

Vault Condition: STS-2 and FBA-23 are located in a very shallow concrete vault. CMG3-T-B borehole depth is -8m.

Site Geology: Sandstone, basalt

Location CodeChannel CodeInstrumentFlagsSample RateDipAzimuthDepth
10BH1Trillium 240 broad bandCG40.000.00356.000.00
00VHZSTS-2 Standard-gainCG0.10-90.000.000.00
00VH2STS-2 Standard-gainCG0.100.0090.000.00
00VH1STS-2 Standard-gainCG0.100.000.000.00
00LHZSTS-2 Standard-gainCG1.00-90.000.000.00
00LH2STS-2 Standard-gainCG1.000.0090.000.00
00LH1STS-2 Standard-gainCG1.000.000.000.00
00BHZSTS-2 Standard-gainCG40.00-90.000.000.00
30LDOCI/PAS pressure sensorCW1.000.000.000.00
20LNZFBA ES-T EpiSensor AccelerometerCG1.00-90.000.000.00
20LN2FBA ES-T EpiSensor AccelerometerCG1.000.0090.000.00
20LN1FBA ES-T EpiSensor AccelerometerCG1.000.000.000.00
20HNZFBA ES-T EpiSensor AccelerometerTG100.00-90.000.000.00
20HN2FBA ES-T EpiSensor AccelerometerTG100.000.0090.000.00
20HN1FBA ES-T EpiSensor AccelerometerTG100.000.000.000.00
10VHZTrillium 240 broad bandCG0.10-90.000.000.00
10VH2Trillium 240 broad bandCG0.100.0086.000.00
10VH1Trillium 240 broad bandCG0.100.00356.000.00
10LHZTrillium 240 broad bandCG1.00-90.000.000.00
10LH2Trillium 240 broad bandCG1.000.0086.000.00
10LH1Trillium 240 broad bandCG1.000.00356.000.00
10HHZTrillium 240 broad bandTG100.00-90.000.000.00
10HH2Trillium 240 broad bandTG100.000.0086.000.00
10HH1Trillium 240 broad bandTG100.000.00356.000.00
10BHZTrillium 240 broad bandCG40.00-90.000.000.00
10BH2Trillium 240 broad bandCG40.000.0086.000.00
00BH2STS-2 Standard-gainCG40.000.0090.000.00
00BH1STS-2 Standard-gainCG40.000.000.000.00
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As part of the annual calibration process, the USGS runs a sequence that includes a random, a step, and several sine wave calibrations.  The USGS analyzes the random binary calibration signal in order to estimate the instrument response.  The figures below show the results from the analysis of the most recent processed calibration at the station.

We use an iterative three-step method to estimate instrument response parameters (poles, zeros, sensitivity and gain) and their associated errors using random calibration signals. First, we solve a coarse non-linear inverse problem using a least squares grid search to yield a first approximation to the solution. This approach reduces the likelihood of poorly estimated parameters (a local-minimum solution) caused by noise in the calibration records and enhances algorithm convergence. Second, we iteratively solve a non-linear parameter estimation problem to obtain the least squares best-fit Laplace pole/zero/gain model. Third, by applying the central limit theorem we estimate the errors in this pole/zero model by solving the inverse problem at each frequency in a 2/3rds-octave band centered at each best-fit pole/zero frequency. This procedure yields error estimates of the 99% confidence interval.

LocChanCal DateEpoch-SpanGradeAmp Nominal Error (dB)Amp Best Fit Error (dB)Phase Nominal Error (degree)Phase Best Fit Error (degree)SensorCal Type
10BHZ2010:310 2010:221 to No Ending TA0.0135280.00722170.106450.081076 TR240Random
00BHZ2010:309 2010:221 to No Ending TA0.0127460.0122560.0705320.068585 STS-2-SGRandom
  1. Current Issues
    LNZ and LN1 channels appear to be bad.
  2. 2010-08-10
    Upgraded to Q330 digitizer.