Testing & Testing Facilities – charge to breakout group

March 25, 2004IRIS Seismometer Workshop 1

Testing & Testing Facilities – charge to breakout group

Who/where are current testing facilities? Do we need more?

Facility design – minimum requirements How to test new designs (e.g. SCG, laser designs,

digital seismometers, etc) What is required to upgrade test facilities to

support new designs? Policies for test facility use and data access Support for test facilities


Current test facilities

Sandia FACT site ASL - USGS Pinon Flat Observatory - UCSD Pinedale Seismic Research Facility - AFTAC Manufacturers Stations Various others

– Black Forest Observatory in Germany

– Conrad Observatorium in Austria

– etc


Current test facilities

Do we need more?– Group favors upgrading ASL and Pinyon Flat (PFO) facilities

as needed

» ASL has granite tunnels & boreholes

» PFO is building new, quieter facility

– Best chance of getting NSF funding for one or both of these facilities


Parameters to be measured (these detemine test facility design req.)

Sensitivity & transfer function Self noise Bandwidth Clip level Stability of sensitivity & transfer function over

time, temperature Cross axis coupling Dynamic range (get from noise & clip level vs. f) Sensitivity to environmental effects

– Temperature, pressure, magnetic field variation, RF. Etc

Shock (shipping survival)


Facility Design – Minimum Requirements

Quiet over all frequency bands of interest Long term reference seismometers operating Shake table capability Isolation table (stable table) Temperature chamber? Use dry ice & John Tsitouris air

circulation technique (less expensive) Auxiliary measurements needed

– Pressure, temperature, wind, magnetic, solar– Small seismic array and/or microbarographic array

High resolution data acquisition systems + other test equipment

Acoustic absorption on walls to reduce acoustic effects on instruments

Capability to test both vault and borehole dryland instruments (implies vaults/tunnels and boreholes)


Facility Infrastructure support

Expert testing personnel Training of new testers and users

– Education and Outreach component

Test equipment Shipping, storage Electricity Network connection Phones Documentation (a set of specific tests and results documented

in a standard way in a report) Etc.


How to test new designs?

Discussion centered on what to do with “inherently digital” seismometers in which the analog signal may not be available

– For proper coherence noise testing, the samples between channels need to be simultaneous (else noise testing needs to be done on isolation table)

– Absolute timing of samples may be an issue– Treat seismometer as “black box” to be tested with available

input (ground motion, cal input) and available output (digital or analog)

How to test Super Conducting Gravity Meters, Laser Interferometer devices not specifically discussed. Characterize as black box (see above).


What is required to upgrade existing test facilities to support

new designs?

Shake tables (both strong and weak motion) Stable tables Higher resolution digitizers may be necessary if

seismometer noise levels go down significantly– Lower voltage rails may also be a problem.

– LSB of 24-bit digitizer with 20 V peak full scale is 2.38 microvolts

– LSB of 24-bit digitizer with 5 V peak full scale is only 0.6 microvolts

– 25-bit resolution (or better) may be necessary


Policies for test facility use and data access

Access– Manufacturers and other users should have open access

– Test facility operator may need to recover costs for lengthy tests

Development testing may be proprietary, so data will be kept confidential unless permission granted by manufacturer

Test data from commercial off-the-shelf (COTS) seismometers will be made publicly available

Data access: Publish on web site and/or appropriate journal (e.g. Seismological Research Letters?)

Security– Site security (such as ASL test facility via Kirtland AFB) may be an

issue for personnel from foreign countries


Support for test facilities

Agency or host organization support– USGS

– UCSD

Possible outside funding sources– NSF

– NIST

– IRIS

– AFTAC

– Manufacturers? Fees for testing? Try to avoid, if possible, except for lengthy, expensive testing programs.

Long term support? Always an issue.


Additional Considerations Proper installation techniques are very important, maybe at least as

important as getting a replacement for the STS-1 Workshop (at ASL? At UCSD?) to continue Standards for

Seismometer Testing (SST) document– Change from “standards” to “guidelines”, add reporting guidelines– Need list of minimum tests to perform for each level of testing (such as

Development, Qualification, Acceptance, Operational, Installation)

Absolute cal technique: Wielandt’s calibration table & software– Table can be purchased from Lennartz or can be built– Software available from Wielandt’s web site:

www.geophys.uni-stuttgart.de/downloads

Tests appropriate for field instruments– Temperature, moisture, physical handling, ease of installation– Field test (install in a real or simulated field experiment)

Severe environment testing – test over range specified by manufacturer or by purchaser for special purposes (e.g. Polar use)

Testing during operation– Calibration through cal coil. How often?– Comparison to reference sensor


More ideas

Strong motion testing– Tilt: Will instrument continue working properly after experiencing

large tilt from local event?– Reproduction of known large displacements (e.g. CalTech pushcart tests

of SM velocity instrument)– Clip level– Hysteresis effects

Clip level testing in general – all sensors Different types of tests

– Development– Design qualification– Acceptance (production units)– Operational– Installation


ASL Location on Isleta Reservation


ASL Seismometer Test Facilities (Boreholes)


ASL Underground Seismometer Test Facility


Testing STS-1 Seismometer in ASL underground vault

Testing & Testing Facilities – charge to breakout group

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