Earthquakes and Faults

Earthquakes and Faults

• A fault is a break in the Earth's crust where significant movement takes place
• Rocks in a fault are stuck together due to friction, but slip when pressure builds up
• When a fault slips, the ground shakes, and this is what causes an earthquake
• The focus/hypocenter is the spot where the fault begins to slip or move
• The epicenter is the spot above the focus
• The footwall is the block of rock that forms the lower half of a fault, always below the fault line
• The hanging wall is the rock that forms the upper half of a fault, always above the fault line
• There are different types of faults, including dip-slip faults, where blocks have shifted vertically, and strike-slip faults, which develop in mid-oceanic ridges
• Normal faults occur when the hanging wall slides down, and reverse faults occur when the hanging wall moves up
• The Philippine fault system and trenches are a system of interconnected faults that run north to south

Earthquake Intensity and Magnitude

• The Richter scale measures earthquake magnitude, with each level indicating 10 times the amount of shaking and 33 times the amount of energy
• A seismograph records vibrations of an earthquake, producing a seismogram
• The Moment Magnitude Scale (MMS) calculates the strength of an earthquake based on the size of the fault, amount of movement along the fault, and rigidness of the rocks
• Intensity measures the strength of shaking and amount of energy released, often using the Mercalli scale

Effects of Earthquakes and Preparedness

• Earthquakes can cause fires, gas leaks, floods, polluted water supply, and damage to bridges and roads
• Earthquake preparedness involves knowing what to do before, during, and after an earthquake

Typhoons

• A typhoon is a strong circular weather system with wind and rainfall, moving counterclockwise
• Hurricanes are equivalent to typhoons in the Atlantic Ocean and the Pacific Ocean
• The Intertropical Convergence Zone (ITCZ) is a region where winds from the northern and southern hemispheres meet
• Conditions that favor typhoon formation include ocean water temperatures above 26.5°C, the presence of ITCZ, low-pressure areas, and light winds
• Typhoons are classified as tropical depressions, tropical storms, severe tropical storms, typhoons, and super typhoons based on wind speed

Tracking and Preparing for Typhoons

• Tropical cyclones are strong if they have warm water and low pressure, and weak if they have land masses and high-pressure areas
• Tracking a tropical cyclone involves knowing its general direction, which is often northwest due to large-scale winds
• The anatomy of a typhoon includes the eye, eyewall, and rain bands
• Typhoon preparedness involves knowing the risks of storm surges, strong winds, extreme rainfall, landslides, and tornadoes
• Tropical cyclone warning signals include Signal 01, Signal 02, Signal 03, Signal 04, and Signal 05, which correspond to increasing wind speeds and danger levels