Earthquakes and Its Hazards

What is the name of the scale used to measure the MAGNITUDE of an earthquake?

• Enhanced Fujita Scale

• Modified Mercalli Scale

• Richter Scale

• Saffir-Simpson Scale

Answer explanation

The Richter Scale, developed by Charles Richter in 1935, is used to measure the magnitude of an earthquake.

What is the name of the scale used to measure the INTENSITY of an earthquake?

• Enhanced Fujita Scale

• Modified Mercalli Scale

• Richter Scale

• Saffir-Simpson Scale

Answer explanation

The Modified Mercalli Scale is used to measure earthquake intensity. It describes the effects of an earthquake, at a given place, on natural features, on industrial installations, and on human beings.

Subduction Zones are areas where tectonic plates ________?

• Transform

• Converge

• Diverge

• Fuse

Answer explanation

Subduction Zones are areas where tectonic plates converge, and one plate is thrust beneath the other.

What is the instrument used to detect and record the slightest movements of the ground?

• Anemograph

• Tiltmeters

• Pyrometers

• Seismographs

Answer explanation

Earthquakes are recorded by instruments called seismographs. The seismograph has a base that sets firmly in the ground, and a heavy weight that hangs free. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not.

How many active faults, located in the Philippines, did we discuss today?

• 4

• 5

• 6

• 7

Answer explanation

We discussed 5 Active Faults. These are the West Valley/Marikina Valley Fault, Western Philippine Fault, Central Philippine Fault, Eastern Philippine Fault, and South of Mindanao Fault.

What type of earthquake hazard is characterized by the sinking or settling of the ground after an earthquake?

• Ground Shaking

• Earthquake-induced Landslides

• Earthquake-induced Subsidence

• Ground or Surface Rupture

Answer explanation

Subsidence occurs when the ground becomes dense after compaction and liquefaction caused by an earthquake. In this hazard, large volumes of earth material are transported by gravity and sink lower into the ground.

What is the name of the phenomenon where loose soil and sediment can behave like a liquid during an earthquake?

Answer explanation

Liquefaction occurs when sand or soil and groundwater mix during an earthquake's shaking. When the two are combined, the ground becomes very soft and has the properties of quicksand. When liquefaction occurs beneath a building, it may begin to lean, tip over, or sink for several meters.

A surface rupture is a zone with variable width where fractures have developed. What do you call the areas affected by ground/surface ruptures?

• Deformation Zones

• Fault Lines

• Subduction Zones

• Ridges

Answer explanation

During surface ruptures, fissuring and displacement of the ground create deformation zones.

In the Philippines, which government agency is principally mandated to mitigate disasters that may arise from volcanic eruptions, earthquakes, tsunamis and other related geotectonic phenomena?

The __________ prepared by the Manila Observatory and the Department of Environment and Natural Resources (DENR) illustrates the country's vulnerability and likelihood of an earthquake.

• Earthquake Hazard Map

• Earthquake Hazard Assessment

• Earthquake Exposure Map

• Earthquake Risk Assessment

Answer explanation

This map identified the 10 provinces that will be most likely hit by an earthquake based on their vicinity to active faults. These are Surigao del Sur, La Union, Benguet, Pangasinan, Pampanga, Tarlac, Ifugao, Davao Oriental, Nueva Vizcaya and Nueva Ecija.