Idaho National Engineering and Environmental Laboratory

Upgrade of INEEL Seismic Stations and Strong Motion Accelerographs to Digital Field Acquisition and Telemetry

HOLLAND, A.A., PAYNE, S.J., BERG, R.G., HODGES, J.M.

May 2003

Idaho National Engineering and Environmental Laboratory

Objectives• Replace analog technology due to rising costs

• Generate an up-gradable off-the shelf system for INEEL seismic monitoring

• Implement digital telemetry to eliminate analog radio noise.

• Improve accuracy of amplitude measurements from seismic monitoring systems

Idaho National Engineering and Environmental Laboratory

INEEL Seismic Monitoring Program

Idaho National Engineering and Environmental Laboratory

System Components at Seismic Stations

• Analog Seismic Station– Typical short-period system with amplifiers, ±5 Volt VCO’s

and 400 MHz telemetry and central 16 bit CUSP acquisition – Sensors: Teledyne Geotech Models S13 & S13J, Mark

Products L4C, and OYO HS-10-B• Digital Seismic Stations

– DAQSystems NetDAS Acquisition Unit– Amplifiers for short-period seismometers (second year of

effort) – Freewave 900 MHz wireless modems– In-house communication specific controller boards– Sensors: Teledyne Geotech Models S13 & S13J, Mark

Products L4C, and Applied MEMS SF1500A, SF2500A, & SF3000L tri-axial accelerometers

Idaho National Engineering and Environmental Laboratory

DAQSystems NetDAS Units

• Industrial PC-104 computer

• Independent 24-bit sigma-delta ADC

– 4 Channel ±20 Volts

– 8 Channel ±10 Volts

• Network based acquisition software and embedded LINUX operating system

• GPS time stamp to an accuracy of 0.001s

• Continuous or triggered recording to compact flash

• User defined acquisition rates

Idaho National Engineering and Environmental Laboratory

•Benefits: –Less radios & antennas –Better management of bandwidth

•Problem: –Error rates were to great to run in the field –Even though lab testing was fine

•Solution –Switched radios to the point-to-point mode –Added radios and serial cards to downstream NetDAS units –Communication method and network routing supported by LINUX operating system

Attempted to operate radios in TDMA (Time Division Multiple Access) mode

–controlled by the NetDAS acquisition software

Digital Telemetry Challenges

Idaho National Engineering and Environmental Laboratory

Assorted Difficulties• Other Issues associated with digital telemetry

– Effects of adverse atmospheric conditions more apparent– Limited number of frequency channels for different links

• Acquisition units would stop communicating over serial port, but would indicate proper operation– Installed a custom board which watches for data packets if

none are seen the system is rebooted– Used pager system to send reboot command to remote

seismic station• System sensitivity was reduced compared to analog system

– Installed 40 dB analog amplifiers to short period seismometers

• Greater power consumption than analog systems– Added battery and solar panel to each station

Idaho National Engineering and Environmental Laboratory

Spread Spectrum Radios

Up to 60 km line of sight and 115.2 kbps

Field NetDAS

Generate network data packets

Continually requests PPP connection

Hub NetDAS

Accepts PPP connections

Routes network data packets

Backup triggering, communication control, and debugging

Earthworm realtime processing, data conversion and exchange

SEISAN post-processing and interactive analysis

Idaho National Engineering and Environmental Laboratory

Idaho National Engineering and Environmental Laboratory

Idaho National Engineering and Environmental Laboratory

Idaho National Engineering and Environmental Laboratory

Benefits of Upgrade • Increased dynamic range from 60 to >90 dB for

high-gain short-period sensors

• Cost and time effective solution for INEEL

• Improved accuracy for instrument response and corresponding amplitude measurements

• Allows recording of acceleration data at remote seismic stations

• Two-way communication with field sites

• Backup for real-time system by recording data at seismic station

Idaho National Engineering and Environmental Laboratory

Continuing Work• Installing NetDAS Strong Motion Accelerographs at

INEEL facilities

• Automatic instrument correction applied to routine data analysis

Idaho National Engineering and Environmental Laboratory

A Few Formalities• This work was supported by the U.S. Department of Energy,

Assistant Secretary for Environmental Management, under DOE Idaho Operations Office Contract DE‑AC07‑99ID13727.

• References herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government, any agency thereof, or any company affiliated with the Idaho National Engineering and Environmental Laboratory.

Idaho National Engineering and Environmental Laboratory

Idaho National Engineering and Environmental Laboratory