Feature: Phivolcs Earthquake Intensity Scale
By: Erlinda Olivia P. Tiu
Wednesday 8th of February 2012
 TACLOBAN CITY, Leyte, Feb 9 (PIA) -- Even ordinary citizens can measure the intensity of an earthquake with the help of the Phivolcs Earthquake Intensity Scale (PEIS), Philippine Institute of Volcanology and Seismology (Phivolcs) Director Renato U. Solidum Jr. said.


The Philippine Institute of Volcanology and Seismology (PHIVOLCS) is the government agency that deals with tectonic and volcanic activities in the Philippines. One of the major concerns of this agency is the monitoring of earthquakes that affects the country.
 
The Philippines is located at the rim of the Pacific Ring of Fire and the country experiences mild earthquakes every day because of this. With the many earthquakes that rock the country every day, how does PHIVOLCS determine if the earthquake is destructive or not? The answer to that is the PEIS.
 
Dr. Solidum took out a piece of folded flyer from his pocket which turned out to be the PEIS which measures how the earthquake is felt in an area. 
 
The PEIS is felt on the relative effect of the earthquake to people, structures, objects, and surroundings. The scale starts from Intensity I, which is the weakest, to Intensity X, which is the strongest.
 
The PEIS flyer showed that an earthquake with:  
 
Intensity I is Scarcely Perceptible. It is scarcely perceptible to people under favorable circumstances. Delicately balanced objects are disturbed slightly. Still water in containers oscillates slowly.
 
Intensity II is Slightly Felt. It is felt by few individuals at rest indoors. Hanging objects swing slightly. Still Water in containers oscillates noticeably.
 
Intensity III is Weak. It is felt by many people indoors especially in upper floors of buildings. Vibration is felt like one passing of a light truck. Dizziness and nausea are experienced by some people. Hanging objects swing moderately. Still water in containers oscillates moderately.
 
Intensity IV is Moderately Strong. It is felt generally by people indoors and by some people outdoors. Light sleepers are awakened. Vibration is felt like a passing of heavy truck. Hanging objects swing considerably. Dinner, plates, glasses, windows, and doors rattle. Floors and walls of wood framed buildings creak. Standing motor cars may rock slightly. Liquids in containers are slightly disturbed. Water in containers oscillates strongly. Rumbling sound may sometimes be heard.
 
Intensity V is Strong. It is generally felt by most people indoors and outdoors. Many sleeping people are awakened. Some are frightened, some run outdoors. Strong shaking and rocking felt throughout building. Hanging objects swing violently. Dining utensils clatter and clink; some are broken. Small, light and unstable objects may fall or overturn. Liquids spill from filled open containers. Standing vehicles rock noticeably. Shaking of leaves and twigs of trees are noticeable.
 
Intensity VI is Very Strong. Many people are frightened; many run outdoors. Some people lose their balance. Motorists feel like driving in flat tires. Heavy objects or furniture move or may be shifted. Small church bells may ring. Wall plaster may crack. Very old or poorly built houses and man-made structures are slightly damaged though well-built structures are not affected. Limited rockfalls and rolling boulders occur in hilly to mountainous areas and escarpments. Trees are noticeably shaken.
 
Intensity VII is Destructive. Most people are frightened and run outdoors. People find it difficult to stand in upper floors. Heavy objects and furniture overturn or topple. Big church bells may ring. Old or poorly-built structures suffer considerably damage. Some well-built structures are slightly damaged. Some cracks may appear on dikes, fish ponds, road surface, or concrete hollow block walls. Limited liquefaction, lateral spreading and landslides are observed. Trees are shaken strongly. (Liquefaction is a process by which loose saturated sand lose strength during an earthquake and behave like liquid).
 
Intensity VIII is Very Destructive. People are panicky. People find it difficult to stand even outdoors. Many well-built buildings are considerably damaged. Concrete dikes and foundation of bridges are destroyed by ground settling or toppling. Railway tracks are bent or broken. Tombstones may be displaced, twisted or overturned. Utility posts, towers and monuments mat tilt or topple. Water and sewer pipes may be bent, twisted or broken. Liquefaction and lateral spreading cause man-made structure to sink, tilt, or topple. Numerous landslides and rockfalls occur in mountainous and hilly areas. Boulders are thrown out from their positions particularly near the epicenter. Fissures and faults rapture may be observed. Trees are violently shaken. Water splash or stop over dikes or banks of rivers.
 
Intensity IX is Devastating. People are forcibly thrown to ground. Many cry and shake with fear. Most buildings are totally damaged. Bridges and elevated concrete structures are toppled down or destroyed. Numerous utility posts, towers and monument are tilted, toppled or broken. Water sewer pipes are bent, twisted or broken. Landslides and liquefaction with lateral spreading and sandboil are widespread. The ground is distorted into undulations. Trees are shaken very violently with some toppled or broken. Boulders are commonly thrown out. River water splashes violently on slops over dikes and banks.
 
Intensity X is Completely Devastating. Practically all man-made structures are destroyed. Massive landslides and liquefaction, large scale subsidence and uplifting of land forms and many ground fissures are observed. Changes in river courses and destructive seiches in large lakes occur. Many trees are toppled, broken and uprooted.
 
With the PEIS as guide, people will know the severity of the earthquake as it happens and will no longer unnecessarily be too anxious. (EOPT - PIA 8)
 
 
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