Seismic Network Operations


Rarotonga, Cook Islands

IU RAR commences operations on: 1992,067

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Host: Institute of Geological and Nuclear Sciences
Latitude: -21.212
Longitude: -159.773
Elevation: 28
Datalogger: Q330
Broadband: KS-54000
Accelerometer: FBA_ES-T_EpiSensor_Accelerometer
Telemetry Status at the NEIC: Last Data In Less Than 10 Minutes
Station Photo Station Photo Station Photo 

Vault Condition: Borehole for Z, N, and E channels. The STS-1/VBB seismometers are located in a small concrete building approximately 20 x 12 feet. Piers are not isolated from the floor, but are attached to surface rock. A small air conditioner inside the building controls temperature and humidity.

Site Geology: To about 85 meters geology is an alternating series of hard basalt and unstable flowing material, scoria, gravels and sands. Below 85 meters there is a consistent sequence of basalts.

Location CodeChannel CodeInstrumentFlagsSample RateDipAzimuthDepth
10BH1STS-2 High-gainCG40.
10BH2STS-2 High-gainCG40.000.0090.000.00
10BHZSTS-2 High-gainCG40.00-
10HH1STS-2 High-gainTG100.
10HH2STS-2 High-gainTG100.000.0090.000.00
10HHZSTS-2 High-gainTG100.00-
20HN1FBA ES-T EpiSensor AccelerometerTG100.
20HN2FBA ES-T EpiSensor AccelerometerTG100.000.0090.000.00
20HNZFBA ES-T EpiSensor AccelerometerTG100.00-
10LH1STS-2 High-gainCG1.
10LH2STS-2 High-gainCG1.000.0090.000.00
10LHZSTS-2 High-gainCG1.00-
20LN1FBA ES-T EpiSensor AccelerometerCG1.
20LN2FBA ES-T EpiSensor AccelerometerCG1.000.0090.000.00
20LNZFBA ES-T EpiSensor AccelerometerCG1.00-
10VH1STS-2 High-gainCG0.
10VH2STS-2 High-gainCG0.100.0090.000.00
10VHZSTS-2 High-gainCG0.10-
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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
10BHZ2012:115 2010:061 to No Ending TA0.0148860.0148380.11870.078267 STS-2-HGRandom
00BHZ2012:114 2010:352 to No Ending TA0.0416520.0402280.389130.42073 54000Random
00BH22012:114 2010:352 to No Ending TA0.022770.00923180.0990510.13694 54000Random
00BH12012:114 2010:352 to No Ending TA0.0227840.00862130.355840.27398 54000Random
  1. Current Issues
    KS-54000 is showing high noise levels.
  2. 2010-12-18
    KS-54000 seismometer replaced.
  3. 2010-03-07
    Upgraded to Q330 digitizer. KS-54000 failed.