Active and Passive MASW Surveys in 1-D, 2-D, and 3-D Formats
Active surveys are performed by using an actively controlled seismic source such as a sledgehammer and an acquisition system consisting of a linear receiver array usually of 24-channels (or more). This type of survey is the most common and can usually achieve an investigation depth of 100 ft or less. Results can be 1-D, 2-D, or 3-D maps showing subsurface distribution of ground stiffness (quantitatively shear-wave velocity, Vs). These maps can show bedrock depth and topography, location of weak zones (e.g., sink-hole hazard or fracture zones), buried boundaries (e.g., landfill, reclaimed zones), and soil characterization, among many other applications.
Passive surveys can achieve investigation depth of several times deeper (e.g., 300 ft), with the field deployment several times bigger as well, than the usual active surveys. The passive remote survey can give a shear-wave velocity profile in 1-D format, whereas the passive roadside survey provides a shear-wave velocity profile in 2-D format.
An area of moderate size (e.g., 200 m x 200 m) can be surveyed in one or two days for an active 2-D survey, and draft results can be obtained within an additional day. The entire project until the final report is available usually takes one week or so. An active 3-D project usually takes a few times (e.g., three times) longer than a 2-D project.
For suitability and feasibility for your project, contact us. We will provide a free consultation and sometimes run modeling experiments to predict the chance of success and possible limitations of your project.
Special Approach for Void and Cavity Detection
Void and cavities are the toughest targets for geophysical investigation especially if they are small (e.g., dimension <= 20% depth below ground surface). We use a special approach (in addition to the normal s-velocity, Vs, mapping) called side scattering analysis (SSA) to detect voids. Results are usually displayed in degrees of probability. Or, voids can be identified from imaged scattering patterns. A large-size cavity or weak zone can be mapped via normal 2-D or 3-D Vs mapping.
MASW Tutorial (In-Field and/or Classroom)
We provide tutorial service in field-operation and/or data-processing of the MASW method. This can take place synchronously as we perform one of your projects in field and classroom, covering basics on the method itself including field strategies, data processing, and interpretation. We can customize the tutorial according to the level of your experience or special focus of your interest.
Highly Flexible Options for Various Projects
The MASW method is one of the most tolerant seismic methods not easily influenced by any adverse noise such as traffic. Therefore, there is a wide range in the optimal field approach including number of channels to be used, types of receivers and array, dimension of site to be surveyed, etc. Based on the field approach and parameters chosen, the MASW method can provide useful information of varying degrees. Please send your questions to us.
Free Consultation on Feasibility and Field Logistics
Once you let us know of what you want to achieve, we will provide a predicted outcome based on the general theory of the method, experience, and sometimes necessary modeling experiment(s). If you plan to run the field survey yourself, we will send schematics of field procedure we recommend. You can send us an email with your questions or to setup a phone consultation.