IRIS PROJECT CHARTER FORM
Title:
IRIS Direct Burial and Auger Sensor Emplacement Tests
Authors: James Gridley, Bob Busby, Jim Fowler
Date:
10 January 2011, 10 May 2011, 23 May 2011
Project Description
We designed this study to address sensor performance for the direct burial (DB) and
auger sensor emplacement (ASP) of seismic sensors and to provide an empirical basis for
evaluating and comparing the different methods of seismic sensor emplacement, with an
impact analysis on future IRIS-supported experiments. This project will conduct of a
series of carefully controlled seismic experiments, data analyses, and engineering
evaluations to determine the applications and value of ASP and DB seismic sensors for
IRIS Instrumentation Services programs.
Stakeholders
IRIS Instrumentation Services, USGS-ANSS, Equipment Vendors, and Seismic Network
Operators.
Background
Seismic sensor emplacement is a key aspect of signal quality and signal to noise for
broadband and very long period measurements. Historically, investigators have assumed
that sensors installed in vaults and wells result in superior low noise floors or superior
signal response. Currently, IRIS PASSCAL supports the procedure of building a small
vault for broadband seismic sensors1 as seen in figure 1. Recent investigations from IRIS
PASSCAL experiments suggest that direct burial may produce reasonable and suitable
measurements for seismic investigations. The IRIS PASSCAL Instrument Center (PIC)
supports these results from recent studies and continues investigating the feasibility of the
direct burial method (see Table 1). Professional literature has plenty of ambient noise
investigations but few studies dealing with seismic sensor emplacement methods, in
particular, the direct burial method. For example, Ringler and Hutt (2010) conducted a
systematic noise study of seismic instruments, but limited the testing primarily to the
ASL2 with only a few borehole tests. Currently, the ASL has extended testing to further
characterize noise.3 This proposed study intends to utilize existing and current testing
procedures and analysis with the inclusion of buried and borehole emplaced seismic
1
For online instructions on the recommended PASSCAL vault construction see,
http://www.passcal.nmt.edu/content/broadband-vault-construction-manual
2
Albuquerque Seismological Laboratory, http://earthquake.usgs.gov/regional/asl/
3
Personal communications with Bob Hutt at the ASL.
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sensors to fill the gap in community knowledge on the effects of different burial and
emplacement methods.
Purpose and Business Need
With the growing size, extent, increase in difficulty permitting sites, and the time and
cost of sensor deployment, there are distinct operational advantages to a direct burial
option. Recent investigations from IRIS PASSCAL experiments suggest direct burial
may be a practical and economically efficient option. Given the potential cycle time and
cost benefits from the direct burial of seismic sensors, this could be a substantial
operational innovation for IRIS PASSCAL investigations, with a potential impact on the
Principal Investigators’ ability to deploy in new areas or with reduced costs.
This document describes the plan for testing and evaluation of sensor performance for the
DB and ASP of seismic sensors against various other deployment methods and more
elaborate vault systems. The evaluation includes various types of burial under different
environmental and engineering conditions, noise levels, and signal response and fidelity.
These analyses further integrates engineering comparisons, cost of installation, and
potential maintenance issues.
The results from this study will be used in future trade analysis of PASSCAL
investigations and other Pan-IRIS programs and efforts.
Project Objectives
Different stakeholders have somewhat different objectives but the general goal of
understanding and characterizing the seismic measurements remains a pan-IRIS interest.
IRIS PASSCAL has a goal to investigate new methods, which will require new or
modified sensors that will improve the success of PI data collection in the field. The
primary objective is to characterize sensor performance for various types of direct burial
methods. Other objectives include, evaluating system engineering performance, cost, and
overall system capabilities within the PASSCAL production cycle. The techniques may
yield lower costs to the PI for an experiment, either because the vault preparation is lower
cost or because it takes less time or manpower. The PASSCAL Program may benefit in
the long-term maintenance and development of the instrument pool. A secondary
objective may be to evaluate whether the existing pool of Broadband sensors can be
adapted to the technique or whether short period sensors might also be deployed
efficiently in this way.
USArray FA goals are similar to PASSCAL and would benefit most if the techniques
were suitable for existing sensors with only slight modification, as few funds are
anticipated in the coming cooperative agreement for recapitalization of equipment.
However, these results will be used to plan a future FA instrument pool for
recapitalization if any funding opportunities arise, or to support USArray TA efforts
specific to Alaska.
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USArray TA is developing plans for deployments in Alaska. The objective of the ASP
study is to maintain or improve seismic noise characteristics while reducing civil works
complexity and be waterproof. In particular, close attention will be placed on the
horizontal oriented noise characteristics and easily repeatable tolerance to field
conditions. A promising approach to large areas of tundra and permafrost is to emplace
the sensor in a 3-5m depth augered hole. The current TA tank design is impractical to
excavate in these regions, therefore a more suitable method must be evaluated. TA will
also encounter regions in the Eastern US with either exposed hard rock (in the north) or
flooded bayous (in the south). Both regions might yield station performance with an
augered (or cored) hole.
This study will produce sets of data with dependent, independent, and known variables
(and no doubt some uncertainties) associated with direct burial as compared to other
methods of seismic sensor emplacement. From these data, the stakeholders will assess
the different types of seismic sensor emplacements against signals of interest, noise,
environment, engineering specifications, and cost.
Assumptions
TBD
Risks
This study will require time and manpower for the different data collection and a
considerable attention to detail and documentation. It is not easy to experimentally vary
and control the relevant variables nor note all the relevant observations, so there in
inherent risk and uncertainty in conducting any seismic experiment. The testing may
result in damage to some equipment. The largest risk in the project is the cost of the
manpower to install and maintain testing which might extend well beyond the anticipated
timeframe due to ambiguous or unrepeatable results.
Plan
We propose to conduct a series of experiments to test and evaluate sensor performance
for the DB and ASP of seismic sensors against various other deployment methods and
more elaborate vault systems.
The plan requires:
1) Sensors capable of being installed in a direct buried method.
2) Cabling and sensor handling tools to level orient and lock a sensor at depth.
3) Holes that represent relevant deployment environments. Some holes may be
serving only to evaluate the sensor handling aspects inserting, removing and
clamping the sensor in the hole.
4) Sensors installed in holes in quiet environments to evaluate noise performance
5) Sensor installed in holes whose environment is similar to intended deploymentsfor example Alaskan permafrost or bayous of Louisiana.
The test will require multiple locations at existing reference systems for periods of time,
up to a year. Results will be evaluated against known deployment methods and will
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summarize relevant environmental conditions and costs. Data and results will be made
available to the scientific community.
Measurements may consist of:
Measurement
Ground Velocity
Wind Speed
Wind Direction
Barometric Pressure
Air Temperature
Soil Moisture
Sensor
Seismometer (2 minimum)
Anemometer
Anemometer
Barometer
Thermometer
TBD
Phenomena
Ground motion
Metrologic
Metrologic
Metrologic
Metrologic
Environment
These observations will be telemetered or forwarded to the IRIS PASSCAL Instrument
Center for archive and analyses.
Site locations will be selected to coincide with existing vaulted systems at one or more of
the following locations:
IRIS PASSCAL Instrument Center
Albuquerque Seismic Lab
Pinedale Seismic Research Facility
Pinon Flat Observatory
Bernallio CA PBO strainmeter test facility
Lajitas TX TXAR Array
USArray TA sites.
At some locations test holes will need to be created. A principal objective of this study is
to characterize sensor performance for various type and methods of sensor emplacement
so, different degrees of success may be suitable to different stakeholders. When
appropriate, locations will be chosen in diverse environmental conditions to evaluate
these important independent variables. In addition, type and nature of burial may vary as
an independent variable and is one of the key technical issues of interest.
There are limited numbers of sensors capable of being inserted for direct burial, so that
two or three types of sensors may be involved in the testing. This may include
participation of the manufacturers in aspects of the design for emplacement-such as case
materials, shape, attachment points, alignment methods, removal techniques as well as
cabling or data analysis. It may complicate interpretation of tests.
The fundamental dependent variable is the seismic performance. For analysis purposes,
we are interested in characterizing the coherent and incoherent noise, the overall noise
level (especially on horizontals) as well as signal response and fidelity, and overall sensor
performance. Ambient noise is suitable for noise analysis, and in most cases, naturally
occurring earthquakes provide the most common signal of interest. But for completeness,
we propose to conduct some basic active source experiments at or near the sites to
provide additional signal response for signal and sensor evaluations.
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Analyses will be conducted through known and established methods, such as PSDs, SNR
estimates, self-noise estimates. These results will also include evaluations of engineering
specifications, environmental conditions, and costs.
Test Plan Outline
Acquire at least two buriable sensor packages
Test those on the pier with appropriate cabling
Create some holes at the PIC for test purposes
Acquire a power auger rig to create additional holes
Utilize existing capability when opportunity allows to create holes at suitable locations
Acquire additional sensors for test purposes.
Install some sensors in holes at PIC
Install some sensors in holes at ASL
Install some sensors in holes at Toolik Lake LTER
Install a suite of sensors in holes at PIC, then ASL
Install a sensor at TXAR, in existing borehole and in new holes created with best known
method.
Install a pair of sensors in Bernallio CA
Schedule
Relative schedule, actual timing is to be determined:
1. Determine sites
2. Get permissions
3. Secure equipment
4. Mock setup at PIC (Huddle Test)
5. Deploy Systems
6. Data verification/validation
7. Receive data for initial analysis
8. Oversee data collection for extended period of time
9. Conduct Analysis
10. Confirm data archive
11. Retrieve Station
Sponsorship
IRIS PASSCAL will be the principal sponsor. However, this project has Pan-IRIS
interest, so we will be looking for collaboration from all the IRIS programs potentially
including the USGS.
Ownership
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The primary stakeholder is IRIS Instrumentation Services and its community, but the
impact crosses all IRIS programs with other international interests. IRIS PASSCAL will
take the lead role with supporting functions from Instrumentation Services.
Resources:
Costs:
(2) existing CMG-3T,
Modified caps, cables
Modified case
Installation tools
Purchase cases for (3) STS-3 or STS-2.5
Purchase (3) Trillium B120
Manpower
Management Plan
Steve Welch will coordinate overall testing, first at the PIC, thereafter will depend on
location. Allan Sauter will coordinate engineering and resources for TA. Mike Fort will
coordinate engineering and resources for PASSCAL. Bruce Beaudoin, James Gridley,
and Bob Busby will direct activities and review results.
Authority
IRIS PASSCAL derives authority from Standing Committee recommendation to BoD,
which in turn may authorize the PASSCAL Manager to pursue this activity at the level
shown below over the next three years. USArray TA has approval from NSF for
engineering work related to planning TA stations in Alaska, the budget for that effort in
the next three years
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Figure 1. Diagram of an IRIS PASSCAL type sensor vault.
Table 1: Recent IRIS PASSCAL Direct Burial Studies.
1 Comparing Background Seismic Noise Levels in TA, FA, and Direct Burial
Stations: Socorro and San Antonio, New Mexico
Nicole D. McMahon (ndmcmaho@mtu.edu) - Internal Report from
PASSCAL Summer Intern 2010.
2 Temporary Broadband Seismic Networks - Comparison of Seismic Noise
levels from a Direct Burial station, Flexible Array and Transportable Array
stations in Socorro, NM - Deployments and Data - Eliana Arias-Dotson,
Nicole D McMahon, Bruce Beaudoin and Noel Barstow (Presented by me at
AGU of the Americas Brazil 2010).
3 Characterization of Station Quality from the Chile RAMP Deployment Direct
Burial (DB) Sensor Installation and its data - Eliana Arias-Dotson, Bruce
Beaudoin, Noel Barstow and George Slad (Presented at AGU Fall 2010).
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Figure 2. Schematic diagram of notional experiment deployment.
References
Ringer, A.T., and Hutt, C.R. (2010). Self-Noise Models of Seismic Instruments.
Seismological Research Letters, Volume 81, Number 6, 972-983, doi:
10.1785/gssrl.81.6.972.
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