Why does the data I downloaded from a USArray TA station look crazy?
Every now and then the data from a USArray TA station I am using looks crazy. It looks like someone hit the sensor with hammer. What’s going on?
There are numerous reasons a Transportable Array (TA) station, or any seismic station, might return data with a crazy signal including but not limited to:
- Field visit: an engineer being on site can introduce unexpected signals, especially if the vault is opened
- Vault settling: as the concrete cures, dirt settles, vault tilts, etc. the sensor may record the movement
- Sensor pings/settling: not uncommon, especially in newer sensors
- Planned station calibration
- Re-centering of sensor masses/feedback loop
- Electrical problems in the sensor, cable or digitizer
Some of these problems are fixable in the field or even remotely. Usually it is not possible to remove the “bad” portion of the signal after it has been recorded.
In order to maintin a high standard of quality the TA data are continuously monitored in near real-time by automated and manual analysis by many groups. The IRIS/USArray program directly funds Quality Control work at the IRIS DMC (USArray QC), the Array Network Facility and the Array Operations Facility at the PASSCAL Instrument Center.