Applied Geophysics Geology 147

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Applied GeophysicsGeology 147

• Lecture 1
• Introduction

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

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

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What is Geophysics?

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• Application of physics to studies of the Earth,
  Moon, and other planets
• Includes Earth, Atmosphere, Oceans, Planetary
  systems

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What is Geophysics?http//seg.org/you-geo/definit
ion.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.

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Examples of Geophysics

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• Pure and Applied Geophysics
• Solid Earth
• Surface Geophysics

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Applied Geophysics (economic objectives)

• Exploration Geophysics
• Engineering Geophysics
• Environmental Geophysics
• Groundwater Geophysics
• Archaeo Geophysics
• Forensics

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Applications?http//seg.org/you-geo/definition.sh
tml

• 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

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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?

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Examples of geophysical methods?

• Gravity

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http//www.vibra-tech-inc.com/content.asp?IDmagne
tics_gravity
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Examples of geophysical methods?

• Magnetics

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http//www.vibra-tech-inc.com/content.asp?IDmagne
tics_gravity
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Examples of geophysical methods?

•     Seismics
•  a.  Reflection
•  b. Refraction
•   c.  Surface or borehole

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Examples of geophysical methods?
    Ground Penetrating Radar

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Examples of geophysical methods?

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• Resistivity

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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

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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 Bo
rehole 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 - Str
atigraphic Mapping 1 2 3 3 - - - Hydrogeologic
Seismic Resistivity EM GPR Magnetics Gravity Bor
ehole Surveys Water Table Mapping
2 1 - 1 - - 3 Water Well Location 2 1 1 2 - 3 2 S
eepage 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 Bore
hole Surveys UTS'S/Drums/Utilities - - 1 1 2 - - L
andfills 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 Res
istivity 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

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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

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Geophysics and Geology

• Geology places constraints on geophysical models
• Geophysics places constraints on geologic
  interpretations

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Planning a Survey - Spatial Aliasing
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Two and Three DimensionsLocation of Profiles
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Survey Noise
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Data Processing - Elimination of Noise
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Displaying Data
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Displaying Data
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Summary

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