Geol 454 Environmental and Exploration Geophysics I Introduction

Geol 454 Environmental and Exploration Geophysics I Introduction tom. h. wilson tom. wilson@mail. wvu. edu Phone: 293 -6431 Department of Geology and Geography West Virginia University Morgantown, WV Tom Wilson, Department of Geology and Geography

General information - handouts • Syllabus (see handout) Hunting for Abandoned Wells • Example paper summary Hunting for caves Tom Wilson, Department of Geology and Geography

General information • Syllabus (see handout) Hunting for Abandoned Wells • Textbook (current status ? ) • Class web page • Grading (32% (pbs), 28% (labs), 10% (paper summaries), 10% (mid term), 20% (final)) • Papers and paper summaries (see handout and link) Tom Wilson, Department of Geology and Geography Hunting for caves

Textbook ? Tom Wilson, Department of Geology and Geography

Geophysics Objectives 1. Obtain conceptual knowledge of the basic theory of gravitational, magnetic, electric, and electromagnetic fields. 2. Develop an understanding of how geophysical observations can be integrated into your discipline or study. 3. Provide analytical experience necessary to oversee applications of these methods in your specialty area. Tom Wilson, Department of Geology and Geography

Geophysics Definitions Applied Geophysics • Making and interpreting measurements of physical properties of the earth to determine sub-surface conditions, usually with an economic objective, e. g. discovery of fuel or mineral deposits. Environmental Geophysics • The applications of geophysical methods to the investigation of nearsurface physico-chemical phenomena which are likely to have (significant) implications for the management of the local environment Sheriff, R. E. , Encyclopedic Dictionary of Exploration Geophysics, SEG. & Reynolds (1997) Tom Wilson, Department of Geology and Geography

Geophysical Methods • Terrain Conductivity • Resistivity • Gravity • Magnetics These methods represent only a few of the various geophysical methods used to peer beneath the surface in a manner. Tom Wilson, Department of Geology and Geography

Terrain Conductivity Inducing current flow – action at a distance Tom Wilson, Department of Geology and Geography

Terrain Conductivity Instrumentation Active Source EM 31 EM 34 Two Commonly used Terrain Conductivity Meters You’ll hear a lot about these in the first 3 -4 weeks of the class Tom Wilson, Department of Geology and Geography

Multifrequency terrain conductivity meter. Same idea Tom Wilson, Department of Geology and Geography

Applications Contaminant Plumes Tom Wilson, Department of Geology and Geography Metal Detection

Abandoned mine lands and mine spoil Tom Wilson, Department of Geology and Geography

Tom Wilson, Department of Geology and Geography

Terrain Conductivity over the Greer Site Tom Wilson, Department of Geology and Geography

Other kinds of instrumentation Gem 2 – Aeroquest/Geo. Phex http: //www. terraplus. ca/products/electromagnetics/gem 2. htm Tom Wilson, Department of Geology and Geography

Resistivity Active source Terra. Plus Case Histories http: //www. terraplus. ca/case-histories/index. html Tom Wilson, Department of Geology and Geography

Resistivity applications Map is contoured in units of 0. 5 percent change, which is a measure of the drop in apparent resistivity from the baseline data set to the data collected after 69 gallons of solution was released. The largest observed percent change in the data was 0. 2%, concentrated near the northeast margin of the tank, and beneath the center of the tank. Tom Wilson, Department of Geology and Geography Underground Storage Tanks Leak detection (Terra. Plus) WESTEC Case Study

Tom Wilson, Department of Geology and Geography

Resistivity measurements made below the liner system Landfill Leak Detection http: //www. terraplus. com/papers/henderson. htm Tom Wilson, Department of Geology and Geography A typical response to an introduced leak is shown on in the figure. This calibration demonstrated that the sensitivity of the particular system was approximately 20 gallons in total introduced leachate, and the location ability of the software was within 10 to 20 feet. This 20 -gallon detection level is equivalent to a 4 -foot-square zone of saturated soil, assuming a 1 -foot thickness.

Gravitational fields Passive source La. Coste Romberg Gravimeter Worden Gravimeter Tom Wilson, Department of Geology and Geography

From Hooke’s Law we get x spring extension ms spring mass k Young’s modulus g acceleration due to gravity Colorado School of Mines web sites - Mass and spring Pendulum measurement Tom Wilson, Department of Geology and Geography

Newton’s Universal Law of Gravitation m 1 F 12 Force of gravity G Gravitational Constant r 12 m 2 Newton. org Tom Wilson, Department of Geology and Geography

We are interested in gobject: some subsurface feature like karst systems, bedrock configuration and groundwater accumulations ms spring mass m. E mass of the earth RE radius of the earth g. E represents the acceleration of gravity at a particular point on the earth’s surface. The variation of g across the earth’s surface provides information about the distribution of density contrasts in the subsurface since m = V (density x volume). Tom Wilson, Department of Geology and Geography

Comparison of bedrock depth map to the residual gravity map Form Stewart Tom Wilson, Department of Geology and Geography Residual gravity map

Magnetic Methods Passive source Magnetic Elements for your location http: //www. ngdc. noaa. gov/geomagmodels/IGRFWMM. jsp Today’s Space Weather http: //www. swpc. noaa. gov/ Tom Wilson, Department of Geology and Geography

Proton Precession Magnetometers Tom Boyd’s Introduction to Geophysical Exploration Course http: //www. earthsci. unimelb. edu. au/ES 304/index. html Tom Wilson, Department of Geology and Geography

See http: //www. earthsci. unimelb. edu. au/ES 304/MODULES/MAG/DESIGN/Mag. Forward. Java. html Tom Wilson, Department of Geology and Geography

Field Operation Coal mine refuse area Tom Wilson, Department of Geology and Geography

Magnetic monopoles p 1 r 12 Fm 12 Magnetic Force Magnetic Permeability p 1 and p 2 pole strengths Coulomb’s Law p 2 Tom Wilson, Department of Geology and Geography

Magnetic Monopoles do not exist. The fundamental magnetic element is a dipole or combination of one positive and one negative magnetic monopole. Tom Wilson, Department of Geology and Geography

Looking for abandoned wells Critical to EOR, EGR, CO 2 Sequestration, fracking and frack water storage and disposal From Martinek Tom Wilson, Department of Geology and Geography

7000 gamma anomaly No excavation planned since the anomaly is located adjacent to a water main From Martinek Tom Wilson, Department of Geology and Geography

Start reading chapter 8 Visit class page at http: //www. geo. wvu. edu/~wilson/geol 454. htm For general background on electromagnetic methods read pages 499 through 514. Most of our work will concentrate on concepts associated with “non-contacting ground conductivity measurements” pages 514 – 518. Tom Wilson, Department of Geology and Geography

Also look over Mc. Neill’s technical note on EM Conductivity/Low induction number Both readings are linked on lecture 1 – see class web page at http: //www. geo. wvu. edu/~wilson/geol 454. htm We will begin discussing basic terrain conductivity theory on Thursday Tom Wilson, Department of Geology and Geography

Any questions? If you are taking the writing section, please remain for a few minutes so we can have a brief discussion and answer any basic questions you may have. Tom Wilson, Department of Geology and Geography

Writing Section – please remain after class Read through the handout with brief question/answer session. Writers should start working on their first paper this week. Tom Wilson, Department of Geology and Geography