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Controlled-Source Instruments
provides support to UTEP at the level of approximately one
FTE. EarthScope’s Flexible Array will also have 1700 TEXAN
instruments upon completion of purchases.
Active-source instruments can acquire large amounts of data
in a short time period. To easily handle the data and make
them easier to archive, PASSCAL is collaborating with the
DMC to develop a new paradigm for archiving active-source
data, based on the data format HDF-5. This new approach
decouples the metadata (geographic and instrument data)
from the seismic waveforms (similar to SEED), permitting
more efficient archiving for PIs and PASSCAL.
Figure 22. Single-channel TEXANs deployed in a dense array at Hill
Air Force Base to image a toxic waste site.
TEXANs
Controlled-source experiments are designed to observe
signals from man-made energy sources, such as explosions,
airguns, and Vibroseis vibrators. The primary data
requirements are for high-frequency recording (up to 500
Hz) at high sample rates (100–1000 Hz) with precise timing.
The REF TEK 125 “TEXAN,” designed and developed by a
consortium of Texas universities and REF TEK, comprises
the largest number of PASSCAL seismic channels used for
controlled-source instruments. The single-channel TEXAN
is small, lightweight (1 kg), runs on D-cell batteries, and
especially easy to use. The typical experimental mode is
to record specific timed segments, synchronized with the
timing of artificial sources, although these instruments are
also capable of recording for several days continuously. The
instruments are often moved to occupy many sites—ease of
deployment and recovery are principal design features.
Multichannel Instruments
PASSCAL maintains ten multichannel recording systems.
These systems are commercial products developed for
high-resolution seismic reflection and refraction experiments,
including geotechnical applications and shallow
petroleum exploration. The PASSCAL equipment consists
of four Geometrics Stratavisor instruments that each record
60 channels, and six Geometrics Geodes each of which
record 24 channels.
PASSCAL currently maintains ~ 550 TEXAN instruments
and supports another ~ 440 through a cooperative agreement
with the University of Texas, El Paso (UTEP). The UTEPowned
systems are routinely used for PASSCAL experiments,
effectively creating a combined pool for the user community.
To maintain access to the UTEP instruments, PASSCAL
Figure 23. Multichannel system recording mining
blasts at the Tyrone Mine, New Mexico.
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