GTSM Technologies


GTSM History

Tensor Strain in California for NEHRP

Tensor Strain in Taiwan

Tensor Strain for PBO / Unavco

Tensor Strain in Japan

Mining Applications

Stability Research

Frequently Asked Questions

Advanced Frequently Asked Questions



Advanced Frequently Asked Questions


GTSM Technologies is located in:




Phone: +61 7 3376 4848

E-mail: GTSM

Why were GTSM strainmeters developed?
What is in a GTSM strainmeter?
What does it look like?
How is strain measured?
Why are there three or four components?
Does the instrument really see what is happening outside the rock?
How is the change in capacitance measured?
What electronics are used to measure the changes?
Why use a split bridge measurement system?

Basic Principles


What Processing is used to produce strain data?
How does the instrument respond to the applied strain tensor?


What kind of electronic calibration is available to monitor gain changes?
To what extent does the process of calibration affect the masurement?
What is the frequency response, especially at the high-frequency end?
Are there any trade-offs between sample rate and sensitivity at any frequency?
Do sample rate changes alter noise levels in the system in any frequency band?
What are the instrumental limitations on dynamic range?
How sensitive is the strainmeter to vertical strain change?

Advanced Calibration

Advanced Calibration
A priori Calibration
Isotropic Calibration
Generalisation of calibration principles – Anisotropic Calibration
How have priori models been validated by field measurements
Have calibrations using coseismic earthquake strain offsets been attempted


What are the diameter, length and weight of the instrument?
How much power is required?
How much power is dissipated in the hole?
What are the major components of a deployed system?
What provisions are made for lightning protection and grounding requirements?
What type of cable is used?
What type of connector is used to feed the cable to the instrument?
Do cable dimensions limit the size of other components that can be placed in the hole?

Responses to Questions

How is the additional redundant component used?
Is the displacement at the capacitor plates different to the displacement of the instrument wall?
Modulus “tuning”
To What extent is it practical to tune the instrument modulus to the site?
How severe a problem is it not to do this?
How is the transformer balanced continuously in the high-frequency version, given that switching is involved in setting the transformer?
The data from the GTSM at PFO (at least) show small changes at the times calibrations are done (every 3 hours, and a larger spike every 10 days), because of increased dissipation. Has this effect been eliminated on later sensors?
Most strain records of earthquakes look similar to velocity seismograms. The data shown seem at odds with this--too much energy in the coda compared to the surface waves. Is there an explanation?
If the digitiser is 16 bit with a least count of 10^-11, this gives peak recordable strain of 0.32microstrain. Is this the effective dynamic range (as apposed to what can be recorded without failure of the sensor)?
What is the total dynamic range that can be accommodated before the response becomes nonlinear or otherwise pathologic?
What effect does "losing" one component channel have on interpreting the data?
Is Lightening damage common?
Is there a method to test the instrument before and after it has been lowered into the hole?

Borehole Issues

What is the required borehole diameter and suggested depth?
What length of ‘‘good rock’’ within the borehole is needed for installation?
Are there environmental limitations e.g. temperature sensitivity, or chemical corrosion?
What conditions would make a borehole unusable?
Siting Issues
What are the specifications for drilling?
Are there unusual requirements that might add to cost or difficulty of installation?
How skilled/knowledgeable does a person have to be to supervise borehole installation?
How much special training in instrument operation will this person need?


Results from Previous Studies

Atmospheric Pressure Response
Rainfall Effects
Results from previous studies
Raw long term data sets?
San Juan Bautista, Northern California
Parkfield GTSM array (Northern California)
Hayward Fault (Chabot)
Pinion Flat tensor strainmeter

Appendix and Bibliography

Appendix & Bibliography