The Power of the Earthquake

The Power of the Earthquake

By José Reyes

I will explain and describe what an earthquake is and make it simple to understand. I will start with the dictionary meaning of an earthquake and in turn, use the terms and concepts to simplify this incredible force of power.

Definition: A sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or volcanic activity.

Layers of the Earth:

Scientist have discovered 3 levels or shells that exists within the earth. The Crust, Mantle, the Outer Core and the Inner Core. The Crust and the Upper-Mantle is where the earthquakes occur.

Tectonic Plates: The crust consists of 12 different rigid plates which are 25 to 100 miles thick and float on top of a more fluid zone, something like the way icebergs float on top of the ocean. Plate tectonics is the continual slow movement of plates.

Faults:

A Fault is a fracture or an area of fracture between 2 blocks of rock. Faults allow the blocks to move relative to each other. Earthquakes occur on faults. The faults surface can be vertical, horizontal, or at some angle to the surface of the earth. The slip direction can also be at any angle. There are 3 types of earthquakes, depending on the 3 types of faults (Normal, Thrust, or Strike-slip).

Instruments To Detect Earthquakes: The instruments used for earthquakes are called seismoscopes and seismographs. The original seismoscope was invented by a Chinese philosopher, Chang Heng (Known as Choko and Tyoko). He invented this device in 132A.D. This was a large Urn with eight dragons on the side. These dragon heads were facing the eight principal directions of the compass. Below each dragon head was a toad with its mouth opened toward the dragon. When an earthquake occurred, one or more of the eight dragon-mouths would release a ball into the open mouth of the toad sitting below. The direction of the shaking determined which of the dragons released its ball. The instrument is reported to have detected an earthquake 400 miles away and was not felt at the location of the seismoscope. No one knows the inside of the seismoscope. Scientists speculate that the motion of some kind of pendulum would activate the dragons.

In the early 18TH century there were several seismoscopes invented. In 1747 Nicholas Cirillo used a simple pendulum to investigate earthquakes in Naples. In the 1800's James Forbes designed an inverted-pendulum "Seismometer".

From 1850 to 1870 there were several significant contributions. Robert Mallet's seismoscope (1852). Luigi Palmieri's "Sismografo Electro-Magnetico" (1856). In 1880 Ewing and fellow seismologists built several seismographs and recorded the 1st earthquake, it was in Japan. In 1935 known as Dr. Quake, Charles Richter invented the magnitude scale. On the Richter Scale, magnitude is expressed in whole numbers and decimal fraction.

Charles Richter

A 5.3 is computed for a moderate earthquake, and a strong earthquake would be a 6.3 on the scale. Each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number. Now scientist use digital seismographs. Magnitude Levels:

1.0 - 3.0	I	I. Not felt except by a very few under especially favorable conditions.
3.0 - 3.9	II - III	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.
4.0 - 4.9	IV - V	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.
5.0 - 5.9	VI - VII	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.
6.0 - 6.9	VII - IX	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.
7.0 and higher	VIII or higher	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.

By studying earthquakes scientists have made images of the earth deep interior, far below the deepest drill holes (5 Miles). By combining seismograms from many earthquakes recorded throughout the world, an image of the earth's interior can be created. The imaging procedure is called seismic technology. It's used in computer-aided tomography (CAT) scan, which doctors use x-rays to create an image of the brain.

Largest Earthquakes Since 1900):

Location: Would be the Epicenter (The exact location where the earthquake occurred).

1.	Chile	1960 05 22	9.5	38.26 S	72.15 W
2.	Prince William Sound, Alaska	1964 03 28	9.2	61.02 N	147.65 W
3.	Andreanof Islands, Aleutian Islands	1957 03 09	9.1	51.57 N	175.34 W
4.	Kamchatka	1952 11 04	9.0	52.75 N	159.50 E
5.	Off the Coast of Ecuador	1906 01 31	8.8	1.0 N	81.5 W
6.	Rat Islands, Aleutian Islands	1965 02 04	8.7	51.23 N	178.52 E
7.	India-China Border	1950 08 15	8.6	28.5 N	96.5 E
8.	Kamchatka	1923 02 03	8.5	54.0 N	161.0 E
9.	Banda Sea, Indonesia	1938 02 01	8.5	5.25 S	130.5 E
10.	Kuril Islands	1963 10 13	8.5	44.9 N	149.6 E

Note: The earthquake in Chile (1960) created a Tsunami (Giant Seismic Tidal Waves) which traveled 6,600 miles, 15 Hours and crashed into Hilo, Hawaii.

Most Destructive Earthquakes:

Date	Location	Deaths	Magnitude	Comments
January 23, 1556	China, Shansi	830,000
July 27, 1976	China, Tangshan	255,000 (official)	8.0	Estimated death toll as high as 655,000.
August 9, 1138	Syria, Aleppo	230,000
May 22, 1927	China, near Xining	200,000	8.3	Large fractures.
December 22, 856+	Iran, Damghan	200,000
December 16, 1920	China, Gansu	200,000	8.6	Major fractures, landslides.
March 23, 893+	Iran, Ardabil	150,000
September 1, 1923	Japan, Kwanto	143,000	8.3	Great Tokyo fire.
October 5, 1948	USSR (Turkmenistan, Ashgabat)	110,000	7.3
December 28, 1908	Italy, Messina	70,000 to 100,000 (estimated)	7.5	Deaths from earthquake and tsunami.
September, 1290	China, Chihli	100,000
November, 1667	Caucasia, Shemakha	80,000
November 18, 1727	Iran, Tabriz	77,000
November 1, 1755	Portugal, Lisbon	70,000	8.7	Great tsunami.
December 25, 1932	China, Gansu	70,000	7.6
May 31, 1970	Peru	66,000	7.8	$530,000 damage, great rock slide, floods.
1268	Asia Minor, Silicia	60,000
January 11, 1693	Italy, Sicily	60,000
May 30, 1935	Pakistan, Quetta	30,000 to 60,000	7.5	Quetta almost completely destroyed.
February 4, 1783	Italy, Calabria	50,000
June 20, 1990	Iran	50,000	7.7	Landslides.

Earthquakes and Volcanoes

Earthquakes may occur in an area before, during, and after a volcanic eruption, but only from the result of the active forces connected with the eruption. Earthquakes do not have any connection in the activation itself, of the Volcano. Earthquakes, at the present time, are unpredictable and do not exhibit any early warnings. Well, I hope you understand earthquakes a little better now.

Learn More:

1.National Earthquake Information Center: http://neic.usgs.gov/

2.Most Recent(Daily): http://quake.wr.usgs.gov/

Comments: SciSim@Cubanology.com