Calibrations

Instrumental response measurement is very important. It is mandatory to retrieve precise ground motion but also to detect malfunctionning sensor.

- Absolute calibration

It allows to retrieve absolute sensitivity of the instruments in V/m/s. The instrument is put on a calibration table CT-EW1 from Lennartz. This table allows a vertical displacement of the seismometer of 900 um. To calibrate horizontal components, an extension bridge is used and the calibration uses the tilt of the instrument.

- Electrical calibration

It is not possible to measure frequency response of the instruments using absolute calibration with the step table. To achieve this, electrical calibration is required. The instruments (STS1 and STS2) have calibrations coils. Ground motion can be simulated by injecting current in those coils. For STS1, a frequency sweep signal is injected to retrieve 2 corner frequencies (High frequency corner at 10-15 Hz and low frequency corner at 360s). Poles and zeros are calculated using Calex-Ew tool from Metrozet.

- jSeisCal

To conduct those calibrations, a tool has been developed in Java : jSeisCal.

Features :

- STS1 installation

- Calibration table remote control

- Q330 data acquisition and recording, file formatting

- Absolute sensitivity calculation

- E300 electronics remote control

Monitoring

- ADBS

ADBS application retrieves data from Adam modules installed in the stations. Those modules digitize different voltages and currents such as : batteries voltage, charge current, station consumption, AC power availability, lightning protection state. The health of the station can be monitored from Paris in real time and problems can be quickly investigated. This system helps preparing interventions from our local contacts.

Measurements are visible through a web page and are stored at least one year.

- Nagios

Nagios application monitors network reachability of each elements in the stations.

Seismic noise

- PQLX

PQLX computes seismic noise by periods of 2H and allows for quality control monitoring.