GEOL 102 Earthquakes and Map

Epicenter

location on the Earth's surface directly above the focus

Fault Surface

Fracture surface between one block and another along which movement occurs

Focus

Origin of the earthquake. The point within the Earth's crust where movement first occurred

Seismic Waves

Waves of energy that travel like shock waves from the focus to the surrounding area

P-wave

Primary / Compression wave. Like a slinky toy. Goes through both liquid and solid (pass)

S-wave

Secondary / Shear wave. Slower. Only pass through solids. Make a shadow zone on the other side of earth. Both horizontal and vertical, can cause a lot of damage.

Strike-slip Fault

Pulls in opposite directions along a plane. Shearing tension.

Normal Fault

Divergent plate boundary, tension, pulling away from each other.

Thrust Fault

Low angle reverse faults. Compression. Expected at convergent plate boundaries.

Reverse Fault

Compression, convergent plate boundary

Seisometer

Instrument that detects seismic waves and records on a paper known as seismogram

Moment Magnitude Scale

Way we measure earthquakes. Used by seismologists, quantitative. More accurate for large earthquakes. Based on energy released.

Richter Scale

Oldest and best known, quantitative scale for measuring earthquake magnitude. Calculated based on difference between P and S wave arrival times.

Natural events that cause Earthquakes

Creation of a new fault, movement along an old fault, movement of magma below the surface or volcanic explosion, landslide

Human made causes of Earthquakes

Underground nuclear explosive tests, fracking, wastewater injection

Elastic Rebound Theory

Energy is stored in the form of elastically deformed rock. When strain exceeds rock strength, the rock fractures and energy is released. Stress, strain, rupture.

Rarefractipn

"bending" of the seismic waves as they move from one material to another of different density.

Moho (Mohorovicic Discontinuity)

Boundary between crust and mantle due to a change in density and composition between the crust and mantle.

Surface Waves

Love waves and Rayleigh waves

Love Waves

Causse horizontal shifting at the surface of the earth

Rayleigh wave

Rotating waves along the surfaces, create vertical displacement, like ripples

Earthquakes at Divergent Boundaries

Shallow within ocean basins. Foci are along mid ocean ridges and transform faults

Earthquakes at Transform Fault

Shallow, and can be very destructive

Earthquakes at Convergent Boundaries

Largest earthquakes occur at subduction zones. Wadati-Benioff Zone. Shallow to deef foci.

Earthquakes at Continent-Continent Convergent Boundary

Generally shallow. Plates collide causing folding and faulting. Creating mountains

Hazards of Earthquakes

Faulting and shaking, landslides, liquefaction, tsunamis, fires.

Liquefaction

Water-saturated sediment behave like fluid. Friction decreases as water moves between particles

Longitude

0 to 180 East or West

Latitude

0 to 90 North or South

Relief

Location where there is a difference in elevation

Hachure contour lines

Show depression

True North (Geographic north)

Direction to the north pole of the Earth, the top of the sphere, where all lines of longitude converge.

Grid North

North used in the grid system (slightly misalignes)

Magnetic North

Direction of north defined by Earth's magnetic field. Constantly moves

Magnetic Field

Extends from the outer core of the Earth into space, creating magnetosphere. It is caused by currents f electricity that flow in the liquid outer core.

Magnetic Declination

Difference in degrees between true north and magnetic north

Lithosphere

Crust and upper most solid mantle, rigid

Mantle

Upper Mantle, asthenosphere, lower mantle; Plastic

Core

Outer is liquid, inner is solid. Mostly Iron

Ring of Fire

Most seismically and volcanically active zone in the world