CMG-3T5TB

CMG-3T5TB

The CMG-3T5TB combines weak- and strong-motion instruments in a single borehole casing.

Features

• Complete CMG-3T and 5T instruments in modular sonde
• Downhole CMG-DM24 digitizer ensures highest data fidelity
• RS232, RS422 or optical links to the surface
• Can be installed at over 500 m depth
• Individual levelling bowls allow installation in boreholes with up to 12 ° tilt
• Weak-motion response from 1 – 360 s to 50 – 200 Hz (120 s – 50 Hz standard)
• Over 200 dB dynamic range

The 3T/5TB was featured in a poster presentation given at EGU 2006.

Options

• Single- or three-jaw hole lock unit for installing in boreholes between 89 and 229 mm diameter
• Built-in inclinometer with separate control unit
• Cable strain relief mechanism (standard if a downhole digitizer is not used)

Dynamic range

Dynamic range of the 3T5TB.

The low noise floor of the CMG-3T components, combined with the 4 g clip level of the CMG-5T sensors, provide an instrument with an effective dynamic range greater than 200 dB over the entire short-period passband.

Weak motion performance

The CMG-3T/5TB uses the same design as the popular CMG-3T instrument.

The plots below estimate the system noise power of the vertical component of the 3T conventional-response sensor. The system noise power, corrected for system response and gain, is shown as a continuous thin line; the circled line is the raw non-coherent power spectrum. The thicker line is the Peterson New Low Noise Model (NLNM).

Measured self-noise of the CMG-3T, vertical component.

Borehole news

	Case study: Borehole array in Japan November 2004 A network of 14 instruments installed as an upgrade to a pre-existing array.
	Very Deep Borehole Installations April 2008 Güralp Systems Ltd. recently delivered and installed two seismic sensors in deep boreholes in California and Japan.
	New borehole instruments for the South Pole December 2006 A new-generation CMG-3TB instrument with adaptations for cold conditions is headed for the South Pole as part of a major upgrade to the world's quietest seismic station.

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