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Are Earthquake's measured differently Here ?

by Ernesto ⌂ @, Troncones, Monday, August 25, 2014, 09:13 (4386 days ago)

Or are Buildings here built to better standards ?
We have a 7.4 Earthquake during Semana Santa and a few Roof tiles fall and a few cracks appear in a few Buildings .
Napa Valley has a 6 and the whole area is Damaged extensively !

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Are Earthquake's measured differently Here ?

by ZihuaRob ⌂ @, Zihuatanejo, México, Monday, August 25, 2014, 09:35 (4386 days ago) @ Ernesto

Or are Buildings here built to better standards ?
We have a 7.4 Earthquake during Semana Santa and a few Roof tiles fall and a few cracks appear in a few Buildings .
Napa Valley has a 6 and the whole area is Damaged extensively !

Ernesto, we use the same Richter scale as is used in California. Hundreds of homes and at least a couple of bridges were destroyed here from the quake on Viernes Santo of this year. Even the church in Petatlán had to rebuild its two towers. The duration, depth and type of movement of the quake has a lot to do with the type of damage seen. The one in Napa Valley was a relatively shallow strike-slip type. The one in Petatlán was a normal dip-slip at, I believe, twice the depth.

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Are Earthquake's measured differently Here ?

by Gringo Viejo @, Kansas/Zihuatanejo, Monday, August 25, 2014, 09:49 (4386 days ago) @ ZihuaRob

All that Rob says is true and there are even more factors. For example the compostiion (solid rock, alluvial(sp) of the area where the earthqueake occurs, the compostion of the earth between the quake and you and the compostion of the earth where you are located have a major effect upon the damage.

And a whole lot more----

Are Earthquake's measured differently Here ?

by Greg in Rocky Mountain House, Monday, August 25, 2014, 09:54 (4386 days ago) @ Ernesto

Rob is correct Ernesto. Earthquake measurements everywhere use the Richter Scale. As measured with a seismometer, an earthquake that registers 5.0 on the Richter scale has a shaking amplitude 10 times greater than that of an earthquake that registered 4.0, and thus corresponds to a release of energy 31.6 times greater than that released by the lesser earthquake. Another factor involved is the distance from the epicentre of the quake.

All I know is

by midalake @, Monday, August 25, 2014, 10:45 (4386 days ago) @ Greg in Rocky Mountain House

That was the longest 45 seconds I ever felt on the 9th floor. Also would not like to have that ride again..............

Dave

More than you ever want to know----

by Gringo Viejo @, Kansas/Zihuatanejo, Monday, August 25, 2014, 11:52 (4386 days ago) @ Ernesto

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That is for sure

by Ernesto ⌂ @, Troncones, Monday, August 25, 2014, 16:30 (4386 days ago) @ Gringo Viejo

My degree doesn't cover this field of study . Gracias a Dios

Modified Mercalli Scale

by mexicowanderer, Monday, August 25, 2014, 23:12 (4386 days ago) @ Ernesto

Richter measurement is fraught with intangibles...

Give a glance at the Modified Mercalli Scale


The Modified Mercalli Intensity Scale

The effect of an earthquake on the Earth's surface is called the intensity. The intensity scale consists of a series of certain key responses such as people awakening, movement of furniture, damage to chimneys, and finally - total destruction. Although numerous intensity scales have been developed over the last several hundred years to evaluate the effects of earthquakes, the one currently used in the United States is the Modified Mercalli (MM) Intensity Scale. It was developed in 1931 by the American seismologists Harry Wood and Frank Neumann. This scale, composed of 12 increasing levels of intensity that range from imperceptible shaking to catastrophic destruction, is designated by Roman numerals. It does not have a mathematical basis; instead it is an arbitrary ranking based on observed effects.

The Modified Mercalli Intensity value assigned to a specific site after an earthquake has a more meaningful measure of severity to the nonscientist than the magnitude because intensity refers to the effects actually experienced at that place.

The lower numbers of the intensity scale generally deal with the manner in which the earthquake is felt by people. The higher numbers of the scale are based on observed structural damage. Structural engineers usually contribute information for assigning intensity values of VIII or above.

The following is an abbreviated description of the 12 levels of Modified Mercalli intensity.

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.

Modified Mercalli Scale

by Gringo Viejo @, Kansas/Zihuatanejo, Tuesday, August 26, 2014, 10:06 (4385 days ago) @ mexicowanderer

I surely have no horse in the race but--
using this scale, it means if there are no people around to feel or man made structures to be damaged then an earthquake cannot/does not occur. Kinda like "if a tree falls in the forest and no one is around to hear it then one asks, does it make any noise?"

Nevertheless this scale does have its usefullness.