What are the relations between seismometer and geophone?
What are the relations between seismometer and geophone?
Microtremor is a kind of weak vibration generated by nature or human activities, with an amplitude of only a few microns to dozens of microns, which can be observed on seismometers.
What is Microtremor Survey?
Microtremor survey is a detection method that collects micromotion signals with specialized seismometers, extracts the dispersion characteristic curve of surface wave signals in its vertical component by digital processing technology, obtains the variation rule of underground shear wave velocity by calculation, and inferences underground structure. The technology uses surface wave components in ground motion signals to extract surface wave dispersion curves and analyze underground physical property differences and geological attribute relationships.
Microtremor survey does not need a vibration source to carry out on-site seismic wave detection, which effectively solves a series of problems such as environmental pollution, safety hazards, and transportation management caused by using explosive sources in previous seismic wave exploration. It has been widely used in engineering investigation, geological surveys, resource exploration, urban geophysical exploration, and other fields.
Applications for Microtremor Survey
Covering layer investigation, geological stratification, and bedrock undulation morphology detection;
Geological structural zone and fissure dense zone detection;
Prospecting for soft strata, permafrost, and sand and gravel layers;
Landslide, ground collapse detection;
Detection of underground caves, karst, goaf, obstacles, and concealment engineering;
Detection of ancient remains and buried objects;
Geophysical Prospecting of shallow oil, gas, and minerals;
Detection of reinforcement effect of foundation;
Geological survey of the seabed.
Instruments for Microtremor Survey
Microtremor survey is usually carried out by a multi-channel micromotion detection system or integrated seismometer. The frequency response range of the instrument should meet the needs of microtremor detection.
Microtremor detection system shall also meet the following requirements:
Channel numbers of the acquisition system should not be less than 4 channels, preferably with 4 channels, 7 channels, 10 channels, or others optional.
The amplitude deviation between channels should not be more than 5%, and the phase difference should not be more than 0.1ms.
Inter-channel crosstalk suppression should not be less than 100dB.
Dynamic range should not be less than 120dB and the A/D conversion bit should not be less than 24 bits.
The system noise is no more than 1µV.
The sampling rate should meet the requirements of detection accuracy, and the acquisition time should be controllable.
The geophones embedded in the integrated seismometer shall meet the following requirements:
Adopt vertical geophone or three-component geophone with voltage output sensitivity not less than 200V/m/s.
For different geophones in a geophone array: the amplitude differences should not be more than 5% and the phase differences should not be more than 0.1ms.
The amplitude difference of the geophones in the same array should not be more than 5%, and the phase difference should not be more than 0.1ms.
The geophone should have a vertically mounted component or horizontal adjusting device.
The underwater geophone assembly shall have the sealing and waterproof ability to meet the detection depth.
More information：
Assorted high-sensitivity geophones: https://www.seis-tech.com/category/geophones/high-sensitivity-geophones/
Integrated Seismometer: https://www.seis-tech.com/eps-portable-digital-seismometer/
