ALPHA Posthole

ALPHA Posthole Seismometer

Product Overview

The posthole version of the ALPHA seismometer can be deployed in the roughest field conditions, from wet surface installations over postholes deployments to sinking the instrument into shallow boreholes. A hermetically sealed and potted mil-spec connector at the top of the seismometer provides the most robust water tightness available, assuring the same performance characteristic as for the ALPHA Surface/Vault version. Two eye hooks and a bracket to attach an installation rod on the seismometer lid allow for secure and easy deployments in post- and shallow boreholes.
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ALPHA Posthole Seismometer

Key Features

Instrument Design

- Classical orthogonal sensor topology with sensor axes pointing in the three cardinal directions.

- Fine pitched adjustable feet manufactured from phosphor bronze.

- Shielded against external magnetic disturbances by mu-metal inside the casing

- Doubled nested feed back loop.

Instrument Characteristics

- Flat frequency response from 0.008333 Hz (120 seconds) to 150 Hz.

- Offered in a whole range of sensitivities from 2*750 to 2*10,000 V/m/s (differential output)

- Operational range within +/- 5.0 degrees of tilt.

- Cross axis rejection >-75dB.


- Rugged housing made from 316 stainless steel material.

- Weight 14.5 kg.

- Dimensions: outer diameter 16.5 cm, height 28.4 cm

- Waterproof as per IP68 standard.

 Power and Electronics

- Power consumption < 1 Watt within the operating range from 9 to 36 Volt.

- Input power is protected against reversed polarity.

- The whole electronic circuitry is two stage galvanically isolated.

To obtain a detailed data sheet for this seismometer, please contact Gaiacode Headquarters

 Disclaimer: The product specifications and the stated data are subject to change without prior notice.

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  • Ref 1 USHER, M.J., BURCH, R.F. and GURALP, C.M., “Wide-band Feedback Seismometers”, 1979. Physics of the Earth and Planetary Interiors, 18: 38-50.
  • Ref 2 M,J, USHER and C.M. Guralp, “The design of miniature wideband seismometer” Geophys. J.R. ast. Soc. (1978)-55 (605-613) ,
  • Ref 3 GURALP, C.M., “The Design of a Three-component Borehole Seismometer”, 1980. Ph.D. Thesis, Univ of Reading.
  • Ref 4 GURALP C.M. Patent Application, No: 7909579 Filed: 19th March 1979 (declaration priority from Appln No: 10279/78 Filed: 15th March 1978) “Vertical Seismometer”.
  • Ref 5 GURALP C.M. United States Patent Application Number: 4,280.206 March 1979. SEISMOMETERS.
  • Ref 6 GURALP C.M. UK Patent Application GB 2-144-287-A. July 1983 Analog-to-digital converters for Seismometers. The National Research Development Corporation (UK)
  • Ref 7 GURALP C.M. UK Patent Application No. 1900719.4; Title: Infrasound Detector [M&S-IRN.FID4315516]