Geophysical Mapping: Method Details
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Method Name: Passive seismic monitoring
Method Type:   Seismic Techniques
Assigned Problems:
+ Earthquakes / paleoseismology Natural Hazards
+ Heat mining Natural Resources
+ Landslides Natural Hazards
0 Fractures Groundwater
   '+' = Technique applicable; '0' = Application possible/limited use
Principle:   Investigation of micro-earthquakes due to fracturing and failure of rock
Keywords:   Seismic Techniques; Passive seismic monitoring; Microseismology; Localization of micro-earthquakes; Frequency-magnitude distribution; Subsurface structure
  • The surveyed area should be larger than the area of interest.
  • Accurate surveying of geometry and topography are required.
  • Ambient seismic noise (e.g., traffic, rain, wind) may reduce data quality significantly.
  • The denser the receiver array, the more accurate is the micro-earthquake localization. Often long-term monitoring (e.g., several months) is necessary to acquire a useful number of micro-earthquakes.
Resolution:   Depends mainly on the released energy of the micro-earthquakes, the receiver coupling, the density of the receiver array and the background seismic noise.
Expected Results:  
  • Measured parameter: Velocity of ground motion (as determined by the voltage generated by the calibrated geophone recording system).
  • Data analysis: NA
  • Interpretation: Additional geological or geophysical surface data may be required for reliable interpretation. Locations of micro-earthquakes in three dimensions, frequency of events, magnitudes.
Combination with other Methods:  
  • Required additional information: Geological information is necessary for the interpretation.
  • Related add-on information: Geological constraints on fracture zones / fault planes.
  • Independent additional information: georadar data.
Operating Expense:  
  • Crew size: 2 - 4 depending on site of investigation and equipment
  • Acquisition speed: 1 - 7 measurements / day depending on site of investigation
  • Processing: > Depending on quality of data and problem set
  • Equipment rental costs: Expenses for installation and maintenance of recording station.
Parameters to specify:  
  • Instrument type (natural frequency; sampling rate; data storage).
  • Receiver array: locations.
QC Documents:  
  • Coordinates and map of shot and receiver locations.
  • Geodetic survey.
  • Accuracy of travel time picks.
  • Daily checks: noise level; impedance of geophones and cables; dynamic range and gain adjustment of seismograph.
  • Field notes (e.g., all activities, effective time schedule, present personnel).
  • Raw data and geometry files.
  • Measurement of noise level.
  • Recordings (particle velocity in three orthogonal directions) with frequency analysis.
  • First-arrival times and / or amplitudes of seismic signals.
  • Subsurface models (depth-distance plots; 2-D and / or 3-D subsurface models).
  • Locations of micro-earthquakes in three dimensions.
  • Interpretation.
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