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Guru
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Earthquake Damage

11/23/2016 6:31 PM

My eldest daughter and family resides in Auckland NZ while her son is teaching in rural Japan. Recently, a 6.3 magnitude earthquake struck ~10 miles from his town at a distance of ~6 mile subsurface. Damage was very light even in the town where the quake occurred; hurrah for earthquake-proof housing structural codes. A similar quake did extensive damage in Amatrice, Italy not long ago.

I have been unable to find information relating Mercalli Intensity Scale (of surface damage) to Magnitude and depth readings. Any help would be appreciated.

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Guru

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#1

Re: Earthquake Damage

11/23/2016 9:06 PM

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

  1. Not felt except by a very few under especially favorable conditions.
  2. Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing.
  3. 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. Vibration similar to the passing of a truck. Duration estimated.
  4. 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.
  5. Felt by nearly everyone; many awakened. some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
  6. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
  7. 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.
  8. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chmineys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
  9. 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.
  10. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rail bent.
  11. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly.
  12. Damage total. Lines of sight and level are distorted. Objects thrown into the air.

http://pubs.usgs.gov/gip/earthq4/severitygip.html

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#2
In reply to #1

Re: Earthquake Damage

11/23/2016 10:40 PM

Given the recent earthquake damage in the photo below from our rail network operator I would call that an 11 or even 12 (although it looks like a major land movement and slip caused this, not the earthquake alone).

Yes that's an intact train track crossing the road and heading on out over the coast.

Fortunately damage as great as this was not widespread, for which we are very grateful !

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#3

Re: Earthquake Damage

11/23/2016 10:42 PM

"Seven Factors That Contribute to the Destructiveness of an Earthquake

A magnitude-6.3 earthquake shook Christchurch, New Zealand yesterday, collapsing buildings, triggering landslides and flooding, and killing dozens of people. A more powerful magnitude-7.1 quake rattled the city last September but didn't cause nearly as much damage, with no fatalities. Why do some e...

By Sarah Zielinski SMITHSONIAN.COM
FEBRUARY 23, 2011 32 13 25 0 14 5 8K 3213014258K

image: http://blogs.smithsonianmag.com/science/files/2011/02/NZintensity-255x300.jpg


A magnitude-6.3 earthquake shook Christchurch, New Zealand yesterday, collapsing buildings, triggering landslides and flooding, and killing dozens of people. A more powerful magnitude-7.1 quake rattled the city last September but didn't cause nearly as much damage, with no fatalities. Why do some earthquakes kill hundreds or thousands of people while others do little damage? There are several factors that determine just how destructive an earthquake can be:
Location: This one is kind of obvious—an earthquake that hits in a populated area is more likely to do damage than one that hits an unpopulated area or the middle of the ocean.
Magnitude: Scientists assign a number to represent the amount of seismic energy released by an earthquake. The Richter magnitude scale, as it is known, is logarithmic, so each step up represents an increase in energy of a factor of 10. The more energy in an earthquake, the more destructive it can be.
Depth: Earthquakes can happen anywhere from at the surface to 700 kilometers below. In general, deeper earthquakes are less damaging because their energy dissipates before it reaches the surface. The recent New Zealand earthquake is thought to have occurred at a more shallow depth than the one last year.
Distance from the epicenter: The epicenter is the point at the surface right above where the earthquake originates and is usually the place where the earthquake's intensity is the greatest.
Local geologic conditions: The nature of the ground at the surface of an earthquake can have a profound influence on the level of damage. Loose, sandy, soggy soil, like in Mexico City, can liquefy if the shaking is strong and long enough, for example. That doesn't bode well for any structures on the surface.
Secondary effects: Earthquakes can trigger landslides, fires, floods or tsunamis. It was not the 2004 Sumatran-Andaman earthquake that caused so much damage in 2004 but the Indian Ocean tsunami it triggered. Nearly a quarter of a million people in 14 countries were killed when coastal communities were inundated by the water.
Architecture: Even the strongest buildings may not survive a bad earthquake, but architecture plays a huge role in what and who survives a quake. The January 2010 Haiti earthquake, for example, was made far worse by poor construction, weak cement and unenforced building codes."

http://www.smithsonianmag.com/science-nature/seven-factors-that-contribute-to-the-destructiveness-of-an-earthquake-44395116/

In summary, there are basically seven factors that determine the destructiveness of an earthquake:

  • Location,
  • Magnitude,
  • Depth,
  • Distance from the epicenter,
  • Local geological conditions (soil conditions),
  • Secondary effects (mudslides, tsunamis, etc),
  • Architecture (building codes)

The last three vary from country to country and are not related to the earthquake strength and location, so I would suspect that there is not a good relationship between amount of damage and the first four factors. I do know that the earthquake in Mexico city was particularly destructive due to geology and the New Zealand quake was less destructive due to Architecture (building codes).

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#4

Re: Earthquake Damage

11/24/2016 7:06 PM

I'm signed up with USGS ENS, the following is what was emailed me right after the event. If you open the event page they have a lot more information and tools to work with. If anyone has family or lives in Pacific Ring of Fire should subscribe to both ESN and the Tsunami Warning

2016-11-21 20:59:49 UPDATED: (M6.9) NEAR THE EAST COAST OF HONSHU, JAPAN 37.4 141.4 (7aa72)

USGS ENS ens@ens.usgs.gov via amazonses.com

Nov 21 (3 days ago)
M6.9 - NEAR THE EAST COAST OF HONSHU, JAPAN

Preliminary Earthquake Report

Magnitude6.9
Date-Time
  • 21 Nov 2016 20:59:49 UTC
  • 22 Nov 2016 05:59:49 near epicenter
  • 21 Nov 2016 11:59:49 standard time in your timezone
Location37.392N 141.403E
Depth11 km
Distances
  • 37 km (22 mi) ESE of Namie, Japan
  • 59 km (36 mi) NE of Iwaki, Japan
  • 72 km (44 mi) E of Funehiki, Japan
  • 80 km (49 mi) SE of Marumori, Japan
  • 243 km (150 mi) NE of Tokyo, Japan
Location UncertaintyHorizontal: 4.7 km; Vertical 2.2 km
ParametersNph = 125; Dmin = 75.7 km; Rmss = 0.86 seconds; Gp = 59°
Version =
Event IDus 10007b88

For updates, maps, and technical information, see: Event Page or USGS Earthquake Hazards Program
National Earthquake Information Center
U.S. Geological Surv

I'm also signed up with the Tsunami Alert System.

[Tsunami Message - IOC] PTWC TSUNAMI THREAT MESSAGE

tsunami-information-ioc@lists.unesco.org

Nov 21 (3 days ago)
TSUNAMI MESSAGE NUMBER 2 2128 UTC MON NOV 21 2016 THE TSUNAMI FORECAST IS UPD...

NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
2221 UTC MON NOV 21 2016
..PTWC TSUNAMI THREAT MESSAGE...
**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****
THIS MESSAGE IS ISSUED FOR INFORMATION ONLY IN SUPPORT OF THE
UNESCO/IOC PACIFIC TSUNAMI WARNING AND MITIGATION SYSTEM AND IS
MEANT FOR NATIONAL AUTHORITIES IN EACH COUNTRY OF THAT SYSTEM.
NATIONAL AUTHORITIES WILL DETERMINE THE APPROPRIATE LEVEL OF
ALERT FOR EACH COUNTRY AND MAY ISSUE ADDITIONAL OR MORE REFINED
INFORMATION.
**** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE *****
THE TSUNAMI FORECAST IS UNCHANGED IN THIS MESSAGE.
PRELIMINARY EARTHQUAKE PARAMETERS
---------------------------------
* MAGNITUDE 7.3
* ORIGIN TIME 2100 UTC NOV 21 2016
* COORDINATES 37.3 NORTH 141.6 EAST
* DEPTH 10 KM / 6 MILES
* LOCATION NEAR THE EAST COAST OF HONSHU JAPAN
EVALUATION
----------
* AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 7.3 OCCURRED
NEAR THE EAST COAST OF HONSHU, JAPAN AT 2100 UTC ON MONDAY
NOVEMBER 21 2016.
* TSUNAMI WAVES HAVE BEEN OBSERVED.
* BASED ON ALL AVAILABLE DATA... HAZARDOUS TSUNAMI WAVES ARE
FORECAST FOR SOME COASTS.
TSUNAMI THREAT FORECAST
-----------------------
* TSUNAMI WAVES REACHING 0.3 TO 1 METERS ABOVE THE TIDE LEVEL
ARE POSSIBLE FOR SOME COASTS OF
JAPAN.
* ACTUAL AMPLITUDES AT THE COAST MAY VARY FROM FORECAST
AMPLITUDES DUE TO UNCERTAINTIES IN THE FORECAST AND LOCAL
FEATURES. IN PARTICULAR MAXIMUM TSUNAMI AMPLITUDES ON ATOLLS
AND AT LOCATIONS WITH FRINGING OR BARRIER REEFS WILL LIKELY
BE MUCH SMALLER THAN THE FORECAST INDICATES.
* FOR OTHER AREAS COVERED BY THIS PRODUCT NO THREAT IS
EXPECTED.
TSUNAMI OBSERVATIONS
--------------------
* THE FOLLOWING ARE TSUNAMI WAVE OBSERVATIONS FROM COASTAL
AND/OR DEEP-OCEAN SEA LEVEL GAUGES AT THE INDICATED
LOCATIONS. THE MAXIMUM TSUNAMI HEIGHT IS MEASURED WITH
RESPECT TO THE NORMAL TIDE LEVEL.
GAUGE TIME OF MAXIMUM WAVE
COORDINATES MEASURE TSUNAMI PERIOD
GAUGE LOCATION LAT LON (UTC) HEIGHT (MIN)
-------------------------------------------------------------
MERA JP 34.9N 139.8E 2206 0.09M/ 0.3FT 08
OFUNATO HONSHU JP 39.0N 141.8E 2207 0.28M/ 0.9FT 12
* THE JAPAN METEOROLOGICAL AGENCY REPORTS A TSUNAMI MEASUREMENT
OF 0.90M AT SOMA JAPAN.

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Guru
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#7
In reply to #4

Re: Earthquake Damage

11/25/2016 11:51 AM

Thanks so much for the "heads up" on the USGS sites. I'm now subscribed and sent them links.

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#8
In reply to #7

Re: Earthquake Damage

11/26/2016 1:02 AM

You may want to check your "ENS" subscription and make sure that you selected Magnitude of ≥3.5 or 4.0 otherwise, your email, phone or both will blow-up!

Yup, Mother Earth is ROCKING

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#5

Re: Earthquake Damage

11/24/2016 10:24 PM

I have friends that live 30 or so miles north of Wellington on the North Island. They have a tree farm and report some minor land slippage in their area. Also many buildings and shopping centers are still closed in Wellington and the suburbs until structural damage is assessed. A goodly number of buildings are already condemned.

My friends property actually sustained more damage due to the torrential rains they had the day after the main earthquake. I have no way of determining the Intensity Scale from the descriptions I have.

Hooker

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Guru
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#6
In reply to #5

Re: Earthquake Damage

11/24/2016 11:34 PM

Here's a couple links to GeoNet and M7.8 Kaikoura Earthquake. There's more info. on their website.

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