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Rockaholic Adventures is the place for conversation and discussion about geologic phenomena and mountaineering excursions. You'll also read reviews written from the perspective of today's technologically-advanced outdoorsman - one with a background in engineering and geology.

Rockaholic Adventures also covers topics such as unconventional oil & gas technologies and environmental geochemistry. The blog's owner, Shawn, is a technical writer at IHS where he writes a quarterly newsletter, Unconventional Oil & Gas News. He graduated magna cum laude in 2006 from the University at Albany where he majored in geology.

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Haiti Aftershock the Week After

Posted January 20, 2010 4:00 PM by Steve Melito

An aftershock of magnitude 6.1 rocked Haiti just over a week after the 7.0 earthquake. The original earthquake, which killed hundreds of thousands of people and disrupted the living circumstances of many more, has been followed by a series of smaller earthquakes.

Will there be anymore aftershocks? That was the question a colleague asked me earlier this morning. I replied that there have been most likely over a hundred aftershocks in Haiti, and that most never made a public statement because they were a hundredth the size.

Earthquakes when measured by the Richter scale (which is most widely used) use a logarithmic scale. The base ten measurements tell you that a 7.0 earthquake is ten times the magnitude of a 6.0 Magnitude. The recent 6.1 aftershock left its impression while the other aftershocks documented by the U.S. Geological Survey (USGS), varying from 4.0 upwards approximately 4.9, have not had nearly the same impact.

After a large earthquake like the one that struck Haiti last week, it is typical to experience several smaller earthquakes, termed aftershocks. These smaller events allow the rigid tectonic plates to elevate any residual stress while the fault line remains lubricated by recent activity. We will most likely see a decline in occurrence and magnitude over the following days, weeks or possibly even months until the activity hibernates in a lower stress environment.

References:

http://www.freakygossip.com/2010/01/earthquake-hits-haiti-2nd-haiti-61-aftershock-latest-updates/

http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/region/S_America.php

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#1

Re: Haiti Aftershock the Week After

01/21/2010 9:46 AM

If I remember correctly, it is typical for any major earthquake to be followed within a few days to a few weeks with an aftershock that is approximately 1 Richter unit below the level of the original quake, for example, a 6.0 aftershock for a 7.0 quake. One of the major problems that contributed to the death toll and major destruction was apparently the use of "poor" concrete and mortar for the buildings. Many Asian countries have strict building codes that use "stronger" concrete for buildings than the average concrete. Does it always seem that the poorer countries are the ones who suffer these casualties more frequently?

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#2
In reply to #1

Re: Haiti Aftershock the Week After

01/21/2010 9:56 AM

The timing and magnitude remains sporadic. I would like to see the statistics on such statements. I know from my background in geology that most accepted computer models for theoretical practices in this field have relatively low correlation to projected outcomes. In the end, these are events that we are unable to predict.

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#3

Re: Haiti Aftershock the Week After

01/22/2010 2:36 PM

After giving some serious thought to the housing issue for Haiti, I have a suggestion- what is normally referred to as "Compressed Earth Block", a technology originating in Colombia in the 1950's to assist in providing housing for indigenous groups of limited means. Most parties currently pursuing this technology are using diesel or gasoline powered hydraulic ram systems to compress the blocks, but the original concept out of Colombia utilised a manually-operated mold with a long, long handle to achieve mechanical advantage and the appropriate compression of the soil. This is called a CINVA ram. Minimal skill is required to determine appropriate soils and proper moisture content. The device is so simple no other special construction skills are needed. Assembling the blocks into walls requires no special motar (using a watery mix of the same soil mixture used for the blocks). No drying, no baking. Quick and easy and something that could be accomplished with local resources. One need not fly in any special materials or equipment, or try to clutter up other relief efforts with this project. Only thing not provided is roofing, and there is likely a lot of scrap material around that could fill the bill, at least on a temporary basis...

These blocks are generally stronger than most concrete blocks one finds in the Third World, and the blocks are mostly waterproof due to high compression (further waterproofing can be achieved with chemical additions, which tends to lessen the advantages of this process, or by applying a conventional stucco finish). Structures of this sort of construction are supposed to be more earthquake resistant than one would expect from more conventional third-world practices.

If I had the resources, I would slap together a couple of these molds, take them to Haiti and start teaching people how to make the molds, and how to build houses with the blocks. This is a solution with long term benefits. Unfortunately, I lack the resources, so anyone else that sees the opportunity here is free to use my idea.

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Anonymous Poster
#4
In reply to #3

Re: Haiti Aftershock the Week After

06/10/2010 11:50 AM

Earth block construction is being done in the community of Deslandes (Artibonite department) in Haiti in a collaborative project involving Partners in Progress (PIP), the Centre d'Intervention Jeunesse (CIJ), and the Instituto Tierra y Cal in Mexico. The main construction project is an elementary school with 12 classrooms in 3 separately constructed buildings. The manual block press being used to make blocks for the first building is an Auram Ram press (from India). The community has also received a hydraulic press from Itel Mexicano that will be used for the construction of the remaining school buildings. PIP and CIJ plan an "earth block" training program that will allow this technology and the experience gained in the school construction to benefit other communities and NGOs operating in Haiti. For more information contact info@PIPHaiti.org.

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