Epicenters, Seismic Waves, and Triangulation

A set of practice flashcards covering epicenters, focus, magnitude, seismic waves (body and surface), triangu lation, and example earthquake details from the notes.

What is the epicenter?

The point on the Earth's surface directly above the earthquake's focus.

What is the focus (hypocenter) of an earthquake?

The point within the Earth where energy is released during an earthquake.

What does magnitude measure in an earthquake?

A number that characterizes the relative size of an earthquake.

What are seismic waves?

Energy released by an earthquake, recorded by seismographs, generated by tectonic plate movement.

What is the difference between body waves and surface waves?

Body waves travel into the Earth's interior; surface waves travel along the crust.

What are P-waves (Primary waves)?

The fastest seismic waves; longitudinal in motion; can move through solids and fluids.

What are S-waves (Secondary waves)?

Slower than P-waves; transverse in motion; can move only through solids.

What are Love waves?

A type of surface wave, the most damaging, moving with horizontal shear; named after Augustus Edward Love.

What are Rayleigh waves?

A type of surface wave that causes rolling, elliptical motion; named after John William Strutt, Lord Rayleigh.

What is triangulation in locating an earthquake epicenter?

A method using data from three seismic stations to determine the epicenter by finding the intersection of circles around each station.

How is distance to the epicenter from a seismic station estimated?

From the time difference between P- and S-wave arrivals; larger difference means greater distance.

How does triangulation determine the epicenter on a map?

By drawing circles with radii equal to each station's distance and locating their intersection.

What recent Balut Island earthquake details were given by Phivolcs?

A 5.6-magnitude earthquake off Balut Island, Davao Occidental; tectonic in origin; occurred at 2:24 p.m. local time.

Can P-waves travel through fluids?

Yes; P-waves can travel through solids and fluids.

Can S-waves travel through liquids?

No; S-waves can travel only through solids.

Which seismic wave is typically the most damaging at the surface?

Love waves.

Which seismic wave is primarily responsible for most shaking felt during an earthquake?

Rayleigh waves.

Who are Love waves named after?

Augustus Edward Love.

Who are Rayleigh waves named after?

John William Strutt, Lord Rayleigh.

What are the two main types of surface waves?

Love waves and Rayleigh waves.