Electrical Methods

Question 1

measure effects of electrical current flow in the Earth.
They include measurements of current flow, electrical potential, and electromagnetic fields.

Answer 1

Electrical Methods

Question 2

Active method measuring electrical potential from subsurface current flow.
Detects pore fluids, clay presence, and quality.

Answer 2

DC Resistivity

Question 3

Often used with DC Resistivity.
Measures transient variations in potential during current application or removal.
Detects clay concentrations and conductive minerals.

Answer 3

Induced Polarization (IP):

Question 4

Passive method measuring naturally occurring electrical potentials.
Associated with sulfide ore weathering and groundwater flow.

Answer 4

Self Potential (SP)

Question 5

Active method measuring time-varying magnetic fields from current flow.
Used in detecting conductive deposits, buried objects, and near-surface mapping.

Answer 5

Electromagnetic EM

Question 6

Passive method using naturally occurring electrical currents from magnetic induction.
Determines electrical properties at great depths inside the Earth.

Answer 6

Magnetotelluric (MT)

Question 7

Defines the relationship between current, voltage, and resistance.
Resistivity measures a material’s ability to transmit electric current, independent of geometry.

Answer 7

Ohm’s Law and Resistivity

Question 8

Lists resistivity values for various Earth materials.
Controlled primarily by pore fluids and fractures filled with fluids.

Answer 8

Resistivities of Earth Materials

Question 9

Requires current source, ammeter, voltmeter, electrodes, and cables.
Considerations for electrode types and avoiding noise in measurements.

Answer 9

Equipment for DC Resistivity Surveys

Question 10

Describes resistivity soundings for depth variations and profiles for lateral variations.
Explains how each survey type detects geologically relevant structures.

Answer 10

(Soundings and Profiles)

Question 11

Wenner survey and Schlumberger survey techniques.
Uses and interpretations for different electrode placements.

Answer 11

Resistivity Soundings

Question 12

Explains log-log plots for resistivity data and their interpretation.
Importance of log-distance schemes for data acquisition.

Answer 12

Electrode Spacings and Apparent Resistivity Plots

Question 13

Details resistivity surveys for identifying vertical structures.
Determining electrode spacings based on underlying structures.

Answer 13

Resistivity Profile

Question 14

Defined empirical relationship between current and voltage.
Established Ohm’s Law for conductive materials.

Answer 14

Georg Ohm’s Contributions

Question 15

T or F: resistivity as a geometrically-independent measure

Answer 15

T

Question 16

is defined as the resistance in the wire, times the
cross-sectional area of the wire, divided by the length of the wire.

Answer 16

Resistivity

Question 17

T or F: High values of resistivity imply
that the material making up the wire is very resistant to the flow of electricity.

Answer 17

T

Question 18

Measured resistivities in Earth materials are primarily
controlled by the movement of

Answer 18

charged ions in pore fluids

Question 19

Passive or Active: DC Resistivity

Answer 19

Active

Question 20

Passive or Active: Induced Polarization

Answer 20

Active

Question 21

Passive or Active: Self Potential

Answer 21

Passive

Question 22

Passive or Active: Electromagnetic

Answer 22

Active

Question 23

Active ot Passive: Magnetotelluric (MT)

Answer 23

Passive

Question 24

Resistivity Soundings detect ______ in resistivity

Answer 24

depth variations

Question 25

esistivity Profiles detect _____

Answer 25

lateral variations

Question 26

Conducted using Wenner or Schlumberger survey types. Vary electrode spacings to assess depth variations in resistivity

Answer 26

Resistivity Soundings

Question 27

Detect lateral variations with fixed electrode spacings. Used for identifying lateral changes like vertical faults

Answer 27

Resistivity Profiles

Question 28

(a device for measuring electrical current)

Answer 28

Ammeter

Question 29

Surveys that are designed to determine resistivity variations with depth above some fixed surface location are referred to as

Answer 29

Resistivity Soundings

Question 30

The most time effective in terms of field work is referred to as a

Answer 30

Schlumberger survey

Question 31

the geometry of electrode placement is referred to as a

Answer 31

Wenner Survey

Question 32

the two current electrodes (green) and the two potential electrodes (red) are still placed in line with one another and centered on some location, but the potential and current electrodes are not placed equidistant from one another.

Answer 32

Schlumberger Array

Question 33

T or F: Traditional plots emphasizes important data at smaller electrode spacings (< 50 meters).

Answer 33

F

Question 34

T or F: Log-log plots decreae visibility of smaller electrode spacing data, facilitating analysis.

Answer 34

F

Question 35

______in log distance, providing well-sampled transition between resistivity extremes.

Answer 35

Evenly spaced

Question 36

i. Resistivity soundings interpreted for horizontally stratified structures ii. profiles for vertical structures.

Answer 36

Both are true

Question 37

Profiles identify can identify ______ indicating vertical contrasts in resistivity.

Answer 37

discontinuities

Question 38

Perform soundings on both sides of the vertical structure to interpret depth variation and set profile spacing.

Answer 38

Soundings Analysis: