MASW Survey In Earthquake Test

- Apr 11, 2019-

The MASW analysis method mainly uses the scattering properties of surface waves in the 1D and 2D shear wave velocity profiles. It is an engineering seismic method that processes distances of several meters to several hundred meters recorded by multi-channel recording systems and receiving devices. 2 to 200 m), data from a few Hz to several tens of Hz (3 to 30 Hz). The seismic surface wave multi-channel analysis method generates surface waves by artificial sources, while the passive seismic surface wave multi-channel analysis method uses surface waves generated by human activities (such as traffic) or natural causes (such as thunder or tidal motion). The exploration depth of artificial seismic methods generally does not exceed 30m, while the depth of exploration of passive earthquakes can generally reach several hundred meters.


      The advantage of the MASW analysis method is that it comprehensively considers the complexity of seismic waves. Seismic waves are always accompanied by noise, such as surface waves, body waves, scattered waves, traffic waves, and unnecessary high-order interference of fundamental-mode surface waves. If these factors are not taken into account, these waves often interact with each other during the analysis of their discrete properties. Using the multi-channel analysis method, the discrete properties of all forms of waves (body waves and surface waves) can be imaged by wave field conversion. The wave field conversion method directly converts multiple records into images and can be used in transforming energy distribution images. See special discrete images. All remaining reflections and scattered waves are automatically eliminated during the conversion process.


     The MASW analysis method is usually divided into the following three steps: (1) obtaining multi-channel wave field records; (2) extracting discrete curves; and (3) inverting these discrete curves to obtain 1D shear wave velocity (VS) profiles. Each 1D shear wave velocity profile is then arranged on a plane to conform to the linear detector arrangement, and a 2D shear wave velocity image is generated by appropriate difference simulation.


    The MASW analysis method is the most common form of surface wave multi-channel analysis and can provide 2D shear wave velocity profile. It uses the horizontal wave propagation properties of the surface wave along the ground to provide 1D or 2D shear wave velocity information. The maximum depth of exploration is usually 10~30m, but it can vary with the source form and size.


      With the popularization of surface wave analysis methods, the requirements for exploration depth have also increased. The use of seismic surface wave analysis requires a lower source frequency (eg, 5-7 Hz). Passive earthquakes use natural or human cultural low-frequency microseisms (1 to 30 Hz) with wavelengths ranging from tens or thousands of kilometers, and exploration depths can be extended to larger.


      MASW analysis is a newly developed seismic analysis method. Compared with conventional high-resolution methods, this method can process seismic exploration data with relatively low relative frequency and deeper exploration depth, and can provide shear waves of near-surface medium. Speed information. Since shear wave velocity information is of great value in geological engineering technology projects, and field acquisition and data processing are relatively simple, this method will be widely applied in engineering exploration.