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Applied Geophysics

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					Applied Geophysics
   Geology 147




     Lecture 1
    Introduction

Photos from http://www.eegs.org/whatis/
Applied Geophysics

     • Identify Geologic Problem
     • Design Survey
     • Acquire Field Data
     • Data Reduction
     • Model Data
     • Interpret Model
     • Write Report




   Photos from http://www.eegs.org/whatis/
      Tonight

•   Greensheet review
•   Textbook
•   What is Geophysics?
•   Applied (Environmental) Geophysics
•   Methods
•   Selection of proper technique
•   Designing a survey
           What is Geophysics?




•Application of physics to studies of the Earth,
       Moon, and other planets
•Includes Earth, Atmosphere, Oceans, Planetary
       systems
            What is Geophysics?
               http://seg.org/you-geo/definition.shtml



•The study of the earth by quantitative physical methods
• Often refers to solid-earth geophysics only, thus
       excluding portions of other subjects
•Exploration geophysics is the use of seismic, gravity,
       magnetic, electrical, electromagnetic, etc., methods
       in the search for oil, gas, minerals, water, etc., with
       the objective of economic exploitation.
Examples of Geophysics




    •Pure and Applied Geophysics
    •Solid Earth
    •Surface Geophysics
    Applied Geophysics
   (economic objectives)

•Exploration Geophysics
•Engineering Geophysics
•Environmental Geophysics
•Groundwater Geophysics
•Archaeo – Geophysics
•Forensics
                  Applications?
          http://seg.org/you-geo/definition.shtml



• Approach to earthquake hazards
• Plate tectonics, the study of the interior
       structure of the earth
•Human's ability to exploit natural resources
•Engineering
•Environmental
•Hydrological
           Geophysical Methods
•   Respond to physical properties of subsurface
    media
•    Can you name some of these properties?
•   Passive vs. active methods
•   A very wide range of powerful tools
•   Can you name some?
Examples of geophysical methods?


                              •Gravity




 http://www.vibra-tech-inc.com/content.asp?ID=magnetics_gravity
Examples of geophysical methods?

                                 •Magnetics




 http://www.vibra-tech-inc.com/content.asp?ID=magnetics_gravity
Examples of geophysical methods?

           Seismics
               a. Reflection
               b. Refraction
               c. Surface or borehole
Examples of geophysical methods?

         Ground Penetrating Radar
Examples of geophysical methods?




                    •Resistivity
            Geophysical Methods

•    Critical to select correct tool(s) for objective –
       either alone or part of a larger survey
•    Need to understand geologic problem, physical
       property to be measured
•    If physical principles are misunderstood, then
       results may be misinterpreted
•    Constraints of Study
    – Geological, Physical, Financial, Temporal
Engineering Evaluation Seismic           Resistivity   EM   GPR   Magnetics   Gravity   Borehole Surveys
Soil/Rock Engineering Properties         1             3    3     -           -         -          -
Excavation Characteristics      1        2             3    3     -           -         1
Foundation Evaluation           1        3             -    3     -           -         1
Utility/Rebar Location          -        3             2    1     2           -         -
Roadway Evaluation              1        2             2    1     -           -         -
Electrical Grounding            -        1             3    -     -           -         -

Geologic                       Seismic   Resistivity   EM   GPR   Magnetics   Gravity   Borehole Surveys
Depth To Rock                  1         2             -    2     -           -         1
Faults And Fractures           1         1             2    2     -           -         1
Sinkholes and Voids            2         1             2    2     -           3         2
Karst Areas                    2         1             2    2     -           3         -
Stratigraphic Mapping &        1         2             3    3     -           -         -

Hydrogeologic                  Seismic   Resistivity   EM   GPR   Magnetics   Gravity   Borehole Surveys
Water Table Mapping            2         1             -    1     -           -         3
Water Well Location            2         1             1    2     -           3         2
Seepage Detection              3         1             2    2     -           -         -
Aquifer Thickness              2         2             3    3     -           -         1
Saltwater Intrusion Mapping    -         3             1    -     -           -         1
Aquiclude Continuity           3         3             2    1     -           -         -

Environmental                  Seismic   Resistivity   EM   GPR   Magnetics   Gravity   Borehole Surveys
UTS'S/Drums/Utilities         -          -             1    1     2           -         -
Landfills and Buried Debris   3          3             1    2     2           -         -
Soil Groundwater Contamination-          2             1    2     3           -         2
Plume Delineation             -          2             1    2     -           -         3
Free Product Detection        -          -             1    1     -           -         -

Mine Planning                  Seismic   Resistivity   EM   GPR   Magnetics   Gravity   Borehole Surveys
Overburden Estimation          1         2             -    -     -           -         -
Sand and Gravel Deposits       2         1             2    2     -           -         2
Clay Layer Mapping             3         2             1    1     -           -         2
           Geophysical Methods

•   May not yield complete answer or unique
    solution; Non-uniqueness of forward modeling

•   Many solutions, but which ones are nonsense,
    which are plausible

•   Interpret within physical constraints &
    geological framework
Geophysics and Geology


             •   Geology places
                 constraints on
                 geophysical models

             •   Geophysics places
                 constraints on geologic
                 interpretations
Planning a Survey - Spatial Aliasing
Two and Three Dimensions
  Location of Profiles
Survey Noise
Data Processing - Elimination of Noise
Displaying Data
Displaying Data
                  Summary

•Course requirements
•Textbook
•Geophysics
•Applied (Environmental) Geophysics
•Gravity, Magnetic, Seismic, GPR & Resistivity
• Selection of proper technique
• Designing a survey

				
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