Photo via WikipediaEarlier this morning after arriving at work, I've read an email sent by a friend, that really caught my attention. In her email, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) announced that a 6.2 magnitude earthquake had hit Cauayan, Negros Occidental (my home province) just 4:47 AM this morning! Another earthquake then had followed after 16 mins, with a magnitude of 5.7 also in Cauayan. At 5:05 AM in the morning, another earthquake occurred at 5.5 magnitude in Dumaguete City, Negros Occidental. And just this afternoon at 4:56 PM, another earthquake strike Cauayan for the third time with a magnitude of 4.9.Magnitude versus Intensity
Magnitudes and intensities are the most two common words we usually hear after an earthquake. But what does these two words meant? And how are these two related with each other?
First thing to know is that magnitude and intensity measures two different things of an earthquake. Magnitude is the measure of energy released at the point or source of an earthquake. It is determined by using a measuring device called seismographs. Intensity on the other hand measures the strength of vibration made by an earthquake at a certain location. Intensity determines the earthquake's effects on people, infrastructures, and the natural environment.
Definition of Levels of Intensities:
I. Not felt except by a very few under especially favorable conditions.
I. Not felt except by a very few under especially favorable conditions.
II. Felt only by a few persons at rest, especially on upper floors of buildings.
III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.
IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.
VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
IX. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
X. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.
XI. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly.
XII. Damage total. Lines of sight and level are distorted. Objects thrown into the air.
From The Severity of an Earthquake.Sources:
So how was the people of Cauayan? Can you update us on this?
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