afrl review, sep 2004 the future of the very broadband sensor s. ingate, et al. the future of the...

AFRL Review, Sep 2004

The Future of the Very Broadband SensorS. Ingate, et al.

The Future of the Very Broadband Sensor

S. Ingate (IRIS)J. Berger (UCSD)J. Collins (WHOI)W. Farrell (SAIC)J. Fowler (IRIS)

P. Herrington (DoE)R. Hutt (USGS)

B. Romanowicz (UCB)S. Sacks (Carnegie)F. Vernon (UCSD)

E. Wielandt (Stuttgart)



The future of the VBB sensor

Should we worry?

Yes!



The VBB sensor is the cornerstone of the GSN

Current research includes:

• “Hum” (fundamental mode peaks 2-7 mHz)

• Low & odd degree elastic structure (e.g., density, Q, etc) from free oscillations

• Tomographic models at level 2 & 4 heterogeneity from normal modes

• Lower mantle lateral density variations

• Rate of relative motion of inner core



The Challenge



Workshop!

Broadband Seismometer

WorkshopGranlibakken Conference

CenterTahoe City, California

March 24-26, 2004

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

•69 attendees•Govt, industry, academe, NGOs•US, Germany, Japan, Canada, France, UK, Russia•Seismologists, physicists, engineers, inventors, managers, owners



Breakout Group I

Requirements, Needs, and Wants• Geophysical (bandwidth, dynamic

range, self-noise)• Borehole or vault design? Life-

cycle of system?• Packaging (power, size, shape,

operating temps) for different environments and survivability

• How many will be needed? By whom (e.g., GSN/FDSN, regional networks, Universities, etc)?

• What is threshold of pain for manufacturing cost?

• Use new technology, or is the triaxial still OK?



Requirements

@ observatories (<0.0001 to ~0.01 Hz)• There are ~ 200?? observatory class stations now

extant less sensitive to cost very sensitive to noise floor better recording of horizontal motion esp

compensating for tilt -( better installation techniques & new types of instrumentation)

need both vault and borehole instruments for existing observatories.

need borehole instruments for ocean floor and islands

need to better understand noise in this band

Intermediate band (~0.01-20Hz)• includes both observatory and portable sensors

(separate)• need lower noise performance above ~ 1 Hz• prefer compact packaging for ease of deployment

for portable versions• need to track metadata (location, orientation)• more price sensitive• Total of XX units over YY years

High Frequency (EQ Engineering)•place in high cultural noise background•Data acquisition system included•need greater sensitivity than now exists•very price sensitive (need <$1K/channel)•low gain velocity sensor desirable•continuous recording

Above ~20 Hzcheap, stable, rugged, watertight, quiet(er)more sensitive than MEMs now offers (at least 10 dB lower - what resolution ?)want to use in arrays and still be cost effective XX units over YY years



Breakout Group II

New Ideas, Concepts, and Designs• Gather a summary of new ideas• What is their potential? How much

will it cost to develop? How long?• Can they be manufactured

reliably? At what cost?• Other factors such as reliability,

OBS use, O&M costs?• Do they need to be complimented

with other sensors?• Life-cycle of components? Will

they be unrepairable in 10 years?



Breakout Group III

Testing and Testing Facilities• Who/where are current testing facilities?• How to test new designs (e.g. SCG, laser designs, etc)?• What is required to upgrade test facilities to support

new designs?• Should test data be made public?• What are we missing (durability?



Breakout Group IV

Academic/Industrial Partnerships• Who are the key players?• What is an appropriate relationship?• Who would be interested?• If a graduate program in sensor design was develop,

would industry be interested? How could they contribute?

• Cross-market utilization? Other programs such as NEES, LIGO, SLA?



Breakout Group V

Educational Perspectives and Funding Strategies• Develop road-map for long-term research• Which funding agencies to target?• If NSF, how to engage ENG/GEO/OCE? Use of matched

funding?• Develop graduate program in sensor design. How to

encourage industry to participate?• Scale of graduate program? Duration, number of

students, cost?• Can new designs be used in other educational

programs? Schools?



Optical Displacement Transducers

(Zumberge et al)

OpticalTiltmeter(Araya)

Laser Strainmeter (Araya)

Laser Interferometer Seismometer (Araya)

LIGO (DeSalvo)

Michelson interferometer & pendulum designs have self-noise below NLNM 50mHz - 100 Hz. Also horizontal long-baseline strainmeter. Gravity wave detectors measure 10e-18 m.



Other Technologies

Magnetic Levitation• By isolating barometric effects,

should approach STS2

Folded Pendulums• Used in accelerometers and gravity-

wave detectors; need to minimise elastic contributions of flexures

Ring Laser Gyro• Installed at Black Forest, New

Zealand and soon Pinon Flat, used to detect variations in G. UCSD will evaluate.

Martian Seismometers• Triaxials on a weight diet

20 cm

Normal PendulumInverted Pendulum

Payload

Frame

Flexures / Hinges



Other Technologies II

MEMS• Full-scale 2 m/s/s, noise floor of

30x10e-9 g/√Hz, $2000 3-axis

Electrochemical (MET)• No springs, could be extended to

1000 sec with new “soft” membrane. Convective diffusion of electrolyte between electrodes is converted to electric current. Hydraulic impedance analogous to Nyquist noise of resistor.

Superconducting Gravimeter• Less noise than STS-1 (5e-3

nm/s), vertical, $100,000



Emerging Technologies

SQUID Displacement Detector• Superconducting Quantum Interference Devices offer 100 x sensitivity than

capacitive devices.

SLAC Strainmeter• Uses 200 remote-controlled fresnel lenses along a 3 km light tube to detect

deformations over its length. Available for experiments.

Quartz Seismometer Suspension• Operate in magnetic environments (SLAC), close to STS-2 performance

Atomic Fountains• Cold atom fountains have accuracy of 10e-9 G, need to scale for geophysical

measurements

Ferro-Fluid Suspension• Suspends magnetic mass to measure ground velocity. Needs to incorporate

force-feedback



What next?

• Report to NSF• Arrange for a presentation to NSF Officers• Within IRIS, continue to monitor emerging

technologies • Continue dialog between IRIS, NSF, industry

and international partners



More Information?

http://www.iris.edu/stations/seisWorkshop.htm

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