ESS Q2 Module 4

The Structure and Composition of the Earth

Earthquake

shaking of the Earth’s surface caused by a sudden release of energy within the lithosphere.

Intraplate earthquakes

Earthquakes can also occur in the middle of plates though these are less common.

flux melting

As the descending plate heats up, it releases water from its minerals and sediments, which lowers the melting point of the overlying mantle rock

Philippine Fault Zone

major left-lateral strike-slip fault, extending about 1200 kilometers

Marikina Valley Fault System

It is divided into two major segments:
• West Valley Fault
• East Valley Fault

East Valley Fault

MARIKINA VALLEY FAULT SYSTEM

A shorter and less active segment

West Valley Fault

MARIKINA VALLEY FAULT SYSTEM

The more active segment that passes through Quezon City, Marikina, Pasig, Taguig, Muntinlupa, and parts of Laguna and Cavite.

“The Big One”

Refers to the potential large earthquake that could occur if the West Valley Fault slips

Taal Volcano

a caldera system known for its violent eruptions

Mayon Volcano

famous for its symmetrical cone and frequent activity

Mount Pinatubo

whose 1991 eruption ranks among the largest of the 20th century

Seismology

the scientific study of earthquakes and the seismic waves they generate.

PHIVOLCS

national agency responsible for monitoring and studying earthquakes and volcanoes

Seismic waves

vibrations that shake the ground and carry information about the earthquake’s source and the planet’s interior. It is mostly produced by natural events

focus or hypocenter

The point underground where an earthquake begins

Epicenter

where shaking is usually strongest. Above the focus.

Body Waves

First to be detected by seismographs after an earthquake.

Travel through the Earth’s interior

P-Waves (Primary)

Fastest Body Wave.

Compressional Waves, push and pull motion.

Travel through solid, liquids and gases.

S-Waves (Secondary)

Slower but more destructive body wave.

Shear Wave, move particles perpendicular to wave’s direction.

Travel only through solids.

Surface Waves

Move along the Earth’s surface

Slower than body waves but cause the most damage

Travel only through solids.

Love Waves

Move the ground side-to-side (Snake-like movement)

Cause buildings to sway or twist.

Rayleigh Waves

Roll along the ground like ocean waves.

SEISMIC IMAGING

A technique that maps subsurface structures by studying how seismic waves bend and reflect through different materials, similar to an X-ray scan.

SEISMIC TOMOGRAPHY

An advanced form of imaging that combines seismic data from earthquakes worldwide to build 3D models of Earth’s interior, similar to a CT scan.