Abstract
The microtremor survey method (MSM) has the potential to be an important geophysical method for identifying the strata velocity structure and detecting the buried fault structures. However, the existing microtremor exploration equipment has been unable to satisfy the requirements of the MSM, which suffers from low data accuracy, long measurement time, and blind acquisition. In this study, we combined a 2 Hz moving coil geophone with advanced acquisition systems to develop a new integrated energy-efficient wireless sensor node for microtremor exploration. A high-precision AD chip and noise matching technology are used to develop a low-noise design for the sensor node. Dynamic frequency selection technology (DFS) and dynamic power management technology (DPM) are used to design an energy-efficient mode. The data quality monitoring system solves the closed technical flaws between the acquisition systems and the control center via 4G wireless monitoring technologies. According to the results of a series of in situ tests and field measurements, the noise level of the system was 0.7 μV@500 Hz with 0 dB attenuation and 220 mW power consumption of the system in the autonomous data acquisition mode. Therefore, it provides substantial support for the effective data acquisition over long measurement durations in microtremor exploration processes. The applicability of the system is evaluated using field data, according to which the integrated energy-efficient wireless sensor node is convenient and effective for MSM.
Highlights
The traditional seismic exploration method makes use of the reflection or refraction at the wave impedance interface during the seismic wave transmission process of underground media
This paper considers high-precision data acquisition system design, energy-efficient mode design, and a wireless online real-time data quality monitoring system for each sensor node in the microtremor exploration
An SD card is used for data storage, which has the characteristics of small size, large storage capacity, and fast data storage speed
Summary
The traditional seismic exploration method makes use of the reflection or refraction at the wave impedance interface during the seismic wave transmission process of underground media. Compared with traditional geophysical prospecting methods, microtremor survey method (MSM) uses the ambient noise of the earth or man-made noise without an artificial source. It is a new noninvasive exploration method with a wide range of potential applications. Microtremor signals are composed mainly of body waves (primary and secondary waves) and surface waves (Rayleigh and Love waves) and the energy of the surface wave is the main component (more than 70 %) of the total energy [1].
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