Near surface passive seismic surveying for mineral exploration, environmental and engineering applications
Passive seismic surveying is a cheap and easy method for mapping depth of cover and shallow stratigraphy in many environments. The use of portable instruments that record seismic vibrations in 3 axial components, in the frequency range of 0.1 hertz (or less) to several kilohertz, and over recording times of 1 to 100 minutes, is becoming more widespread in the minerals exploration and engineering industries. These instruments can be used to cost effectively estimate the thickness and shear wave velocity of loosely consolidated, transported regolith or highly weathered bedrock regolith layers sitting above fresh bedrock to a maximum depth of around 500 m. By analysing surface wave (‘ground roll’) data in the frequency domain, it is possible to estimate the thickness of low shear wave velocity material above higher velocity substrate where there is a significant contrast in seismic impedance. The various passive seismic surveying methods involve measuring surface wave propagation with an array of sensors, or resonance frequencies of Raleigh waves using a single sensor. The ambient seismic energy is derived from natural and manmade sources coming from all directions. Survey results are most reliable when velocity vs depth models and frequency vs depth data are locally calibrated to geological layers and bedrock depths from boreholes. The workshop presentations feature a number of seismometer types and survey configuration styles available for acquiring passive seismic data, along with the theory behind the passive seismic method, data recording and processing, and noise analysis conventions. Most emphasis is placed on the H/V peak frequency method for rapid surveying, with some review of SPAC and FK methods.
Presentations on this page were kindly provided by presenters at a workshop held as part of the 25th Geophysical Conference and Exhibition in Adelaide, South Australia, held in August, 2016. Workshop material discusses calibration and modelling, anisotropic ground conditions, seismic sources, pitfalls, and a number of Australian and overseas case studies of mineral exploration applications. The workshop was convened by Jayson Meyers and Chris Wijns.
- International eperience with passive seismic (ambient noise) methodology (Michael Asten)
- Applications of TROMINO: HVSR and more (Jérémy Magnon)
- State-of-the-art in passive seismic array methodology (Nick Smith)
- HVSR case studies galore to help curb your scepticism (Jayson Meyers)
- Passive Seismic for mapping and estimating the depth of paleochannels (Matt Owers)
- Depth of Kalahari cover in Botswana (Chris Wijns)
- Benchmarking passive seismic estimates of cover-thickness (Alexei Garbatov)
- Passive seismic surveying over weathered geology with poor impedance contrast, and other complicating factors (Nigel Cantwell)
- Shallow Level Passive Seismic at GSWA; surveys and storage (Ruth Murdie)
- Cover thickness investigations in the Albany-Fraser, Western Australia (David Stannard)
- Passive sesimic for drill-hole optimisation; from Cretaceous cover to tundra thickness (Andrew Fitzpatrick)
- Passive seismic for delineation of concealed channel iron deposits: Dream or reality? (Kevin Stephens)
- Energy Sources for Passive Seismic Imaging (Anya Reading)