reflection methods and results geophysics 492/692

Reflection Methods and ResultsGeophysics 492/692

Josh Michaels, Zach Reynolds, Nick Prina, Molly HunsakerSurvey run by Dr. Lee Liberty of Boise State University

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Line 4 Location MapLakeside Drive and Manzanita Lane to the north corner of Jasper Lane and Manzanita Lane.

Methods 1 meter geophones and source intervals Usually 3 shots at each source location Seismographs record each shot

individually› Not stacked in the field

Used rollbox to keep the source centered› Excluding the ends of the line

Processing Data Line 4 = 887 total shot records of 120 traces each Processed using JRG and Viewmat (v. 3.6.3) Selected records examined with a range of bandpass filters

› Designed to maximize reflections and minimize other seismic waves and noise

› 20-100 Hz (10% dip) optimal for reflections in Line 4 Individually examined every record; removed any traces

that failed our criteria› Non-functioning or incorrectly functioning geophone traces› Bad records caused by a misfired trigger on the source, indicated by no

coherent seismic wave pattern › Strong hyperbola patterns caused by movement along the reflection line

during recording

Record 8064

Processing Data Line 4 = 887 total shot records of 120 traces each Processed using JRG and Viewmat (v. 3.6.3) Selected records examined with a range of bandpass filters

› Designed to maximize reflections and minimize other seismic waves and noise

› 20-100 Hz (10% dip) optimal for reflections in Line 4 Individually examined every record; removed any traces that

failed our criteria› Non-functioning or incorrectly functioning geophone traces› Bad records caused by a misfired trigger on the source, indicated by

no coherent seismic wave pattern. › Strong hyperbola patterns caused by movement along the reflection

line during recording. Constant velocity stacking

› Ranged from 500 to 3500 m/s (100 m/s intervals)› Stacking reduces random-sourced signals

Dix Velocity Intervals

NMO Interpolated velocity

Dip-filtered CMP stack

Dashed black lines = interpreted faults

Green shapes = artifact errors

Frequency Analysis

From the unfiltered CMP stack Dominant frequencies at ~30Hz

Improvement? More controlled acquisition

environment Geophone functionality Removal of 60 Hz electrical noise

› Known to exist, but not dominating signal More thorough velocity model Our results are only preliminary

› Pre-stacked depth migration