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Method Name: |
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Passive seismic monitoring |
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Method Type: |
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Seismic Techniques
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Assigned Problems: |
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Principle: |
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Investigation of micro-earthquakes due to fracturing and failure of rock |
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Keywords: |
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Seismic Techniques; Passive seismic monitoring; Microseismology; Localization of micro-earthquakes; Frequency-magnitude distribution; Subsurface structure |
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Prerequisites: |
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- 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.
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Resolution: |
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Depends mainly on the released energy of the micro-earthquakes, the receiver coupling, the density of the receiver array and the background seismic noise. |
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Expected Results: |
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- 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.
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Combination with other Methods: |
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- 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.
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Operating Expense: |
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- 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.
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Parameters to specify: |
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- Instrument type (natural frequency; sampling rate; data storage).
- Receiver array: locations.
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QC Documents: |
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- 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).
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Products: |
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- 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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