Why use different kinds of strain meter?
For large scale long term motions of the earth such as is used to map the large scale motions of the earth in major fault zones, GPS based strain measurement is ideal. The limitation of these measurements are that short term deformations cannot be adequately measured because of the noise in the data due to atmospheric effects and near surface ground noise. GPS is best for mapping long term phenomena. For higher sensitivity studies critical for observation of the short term (minutes to months) strain changes which are very common, borehole strain meters which operate at several hundred times higher sensitivity are necessary. The GTSM system was developed to study these phenomena.
