Exploring the Fundamentals of Applied Geophysics

Introduction to Applied Geophysics

• Applied geophysics involves studying the Earth's physical properties using methods of physics.

Exploration Geophysics

• Focuses on exploring subsurface structures and resources such as oil, gas, minerals, and groundwater.
• Uses various methods, including seismic, electrical, electromagnetic, and gravitational methods.

Petroleum Exploration

• Main method used: Seismic method, which measures physical properties such as velocity, density, and elasticity of the Earth's subsurface.

Soil Mechanics

• Field of applied geophysics: Engineering geophysics, which studies ground properties and provides development plans for soil mechanics.

Environmental Geophysics

• Purpose: To assess and mitigate environmental hazards such as contaminant plumes, landfill sites, and buried infrastructure.

Mineral Exploration

• Commonly used method: Electromagnetic method, which measures the electrical conductivity of formations or rock bodies.

Physical Properties Measurement

• Seismic method: Measures velocity, density, and elasticity of the Earth's subsurface.
• Electric method: Measures the electrical conductivity of formations or rock bodies.

Gravity Method

• Measures variations in the strength of the gravitational field, associating variations with differences in the distribution of densities and rock types.

Electromagnetic Method

• Measures the electrical conductivity of formations or rock bodies.

Seismic Survey

• Application: Exploration and monitoring of subsurface structures and resources.

Engineering Site Study

• Suitable methods: Seismic, electrical, and electromagnetic methods.

Geophysical Survey Methods

• Seismic method: Based on the principles of seismology, estimates the properties of the Earth's subsurface from reflected seismic waves.
• Electrical method: Provides information on formations or rock bodies that have electrical conductivity.
• Electromagnetic method: Measures the electrical conductivity of formations or rock bodies.
• Gravitational method: Measures the gravitational field to associate variations with differences in the distribution of densities and rock types.
• Magnetic method: Measures the local geomagnetic field produced by variations in the intensity of magnetization in rock formations.
• Refraction method: Utilizes refracted waves to map subsurface structure, and was used extensively for oil prospecting before being replaced by the reflection method.