GWP - SEISMIC PROSPECTING

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Artificial seismic register. The gray zone belongs to a salt vault associated with petrol

Field Phase

* Microseismic generation
* Mechanical waves register through geophones
* Generation of Dromochronic graphics ("Road-time")

Study Phase

* Identification of different waves: Compression, Rayleigh's, etc.
* Deduction of the subtopography and the elastic constants through the Continuous Medium Theory


EARTHQUAKES: TO CONTROL OR TO PREDICT?

Facing natural disasters (hurricans, earthquakes, etc.) mankind has always had two alternatives: try in same way to control the phenomenon or to recognize that nature is more powerfull and only to predice (it implies a passive resignation attitude when allowing the phenomenon occurs)

HOW EARTHQUAKES HAPPEN?
The cortex is formed by tectonic plates that float in the "magma" (hot and semiliquid rocks). The contact zone between two plates is called "fault". If the plates slip slightly one over the other (or in other words, if the friction were light) we would have an amount of shakes... slight and harmless. Unluckily in the faults there is a great friction that keeps them in its place, while the vortices of magma ("convection currents") produce a continual pushig which is shown as increasing pressure.
So, when the accumulated forces exceed the friction, there is a violent shake because of a strong movement of the plates. That is what can be called an earthquake.

On other side, to settle a city is preferable that the climate and the natural means of transport be favorurable. This leads us to coasts, valleys and riversides, it means... on the faults. Effect? A 40% of the cities in the world are in seismic zones. Just one quake can cause thousands of deaths:
* 1976, Tangshan, China: 250 000 deaths
* 1978, Iran: 15 000 deaths
* 1985, Mexico City: 30 000 deaths
* 1988, Armenia: 25 000 deaths, etc.

MORE...


More Articles
* Altiplanian Supervolcano (October, 2012)
* Diseño antisìsmico (enero de 2011)
*
Crustal motion in the zone of the 1960 Chile earthquake
* Predicción Científica de Sismos (Jun 05)

* Seismic Lagoon in Chile (Jan 04)
* Tiembla en el Mundo (Sept 04)
* La Luna gatilla terremotos (Dec 04)
* Terremoto en el Norte Grande (jun 05)
*
Earthquake in Sumatra (dec 05)
*
The Earthquakes Generating Machine
*
California: Earthquake Forecasting System
*
Valdivia Earthquake (Nature, sept 05)

 

   

Elastic Constants

Material
Reluctance to Compression, N/mm2

Reluctance to Traction, N/mm2

Young's Module, N/mm2
Steel
552
827
207 000
Bone
170
120
17 900
Granite
145
4.8
51 700
Porcelain
552
55
(frágil)
Oak
59
117
11 000
Concrete
21
2.1
16 500

Outstanding Historical Seisms

To think up...

* May 22nd 1960: the severest earthquake in human history. Epicentre: Mocha island. The length of the break 1000 Km; Ms magnitude 8.6... SATURATED (!)
* March 3rd 1985. Earthquake in front of Valparaiso. Length of the break 170 Km; Ms magnitude 7.8

Seismic rings. Near 80% of the volcanic eruptions happen in the Pacific Fire Ring.
The seisms epicenters are, in its great majority, distributed in the strips designated as Alps Ring and Circum Pacific Ring ("Pacific Fire Ring") which correspond to the edges of the tectonic plates where most of the pressure is accumulated. Above them the most outstanding mountain ranges are formed: The andes, The Alps, The Himalayas, etc.


MYSTERY:
What phenomena could anticipate the incidence of a seism?