Shear Zone Exploration With Ambient Seismic Noise


In Shear Zone Exploration With Ambient Seismic Noise, the objective is to discover and map shear zones through the use of passive seismic exploration techniques based on surface waves.


A “shear zone” is a zone of closely spaced, approximately parallel faults that often channel solutions in the subsurface and may host large mineral deposits.

Shear Zone Exploration With Ambient Seismic Noise. Structure illustration.
Illustration of a shear zone, compared to an initial configuration, a single fault, and a fault zone.


  • Obtaining the shear wave velocity structure (Vs) in 1D, 2D and 3D, or monitoring over time (4D) by means of tomographic imaging techniques based on recording and analysis of surface waves by interferometry.
  • Shear zones appear as sectors of low shear wave velocity (Vs). The edges of the shear zone are evident in the drastic change in seismic velocity.
  • Depth of investigation and resolution determined, among other factors, by the nature of the noise, design and coverage of the sensor array, and seismic noise bandwidth.
Shear Zone Exploration With Ambient Seismic Noise. Velocity Models examples.
Examples of shallow shear zones images obtained with ambient seismic noise.


  • As it is a passive seismic technique, the factors inherent to active sources, such as perforation, power, permits and transportation, among others, are non-existent.
  • Because the presence of environmental seismic noise can have a very large distribution and coverage, passive seismic is feasible at local, semi-regional, and even regional scales in both urban and remote settings. So, even far from urban environments and anthropic noise, the technique is feasible taking advantage of natural surface noise sources, such as waves, river flows, wind, and even earthquakes generated in tectonically active areas in the vicinity of the study area.
  • Low acquisition costs compared to active seismic methods, even those from a non-explosive source.
  • From surface waves, we have the ability to map lateral or vertical variations that correspond to low-velocity intervals, associated with faults, fractures, or shear zones.
  • Minimal or non-existent environmental footprint.
Shear Zone Exploration With Ambient Seismic Noise. Noise spectra.
Spectrum of ambient seismic noise at (a) Tucson, Arizona and (b) Barro Colorado Island, Panama (McNamara y Boaz, 2019). Note that long-period Earth hum due to resonant oscillations of the planet is detected in Arizona, and long-period noise due to large vessel traffic crossing the Canal (“seiche”) is detected in Panama.


  • Range in depth determined by the quality (amplitude and frequency) of the seismic noise present in the area.
  • The feasibility, for semi-regional or regional studies, depends on nodal acquisition systems with prolonged autonomy. Wired seismograph systems have little feasibility of being used in large-scale (semi-regional or regional) surveys.
Shear Zone Exploration With Ambient Seismic Noise. 2D and 3D models.
Example of results obtained with the Ambient Seismic Noise Tomography technique. Vertically (a) and horizontally (b) polarized S-wave velocity models. Vertical distribution of velocity anomalies (c). Geological model based on environmental seismic noise (d). Note the achieved depth of investigation of 20 km. Modified from Jaxybulatov et al. 2014.
Shear Zone Exploration With Ambient Seismic Noise. Subsurface mapping.
Vs velocity model from seismic noise at 200 m depth over local topography. Fault traces are shown with white lines. Orange/red areas indicate slower than average speed zones. Green/blue areas indicate faster than average speed zones. Modified from Mordret et al, 2019.


Our company is ideally suited to be your ally in Shear Zone Exploration projects Based on Ambient Seismic Noise for various reasons:

  • We have hundreds of autonomous Quick nodes with very low instrumental noise, which is essential to reliably record seismic noise.
  • We are experts in quality control of environmental seismic noise, thanks to internal developments such as the SPAC RT software.
  • We accompany our clients in the acquisition design phase, modeling the seismic noise scenario, possible frequencies, and depth of investigation to be achieved with the Ambient Seismic Noise Tomography technique.

F min
Garnet Biotite Sillimanite Gneiss4.200.251.732.421.00.8
Garnet Biotite Gneiss4.500.251.732.591.00.9
Graphitic Mica Schist4.700.251.732.711.00.9
Mylonite zone5.250.251.733.031.01.0

Example of expected depth of investigation (DOI) modeling results, executed by Subsuelo3D for a major mining client.