Ethiopian Association of Geoscience (EAG)
1.63K subscribers
590 photos
22 videos
371 files
1.15K links
Discuss 👉 @EAGDiscussionPlatform
Ethiopia | Geology | Association
Mineral | Mining | Groundwater | Higher education | Consult | Hydrogeology | Job | Geothermal
Download Telegram
#GeneralKnowled | Seismometers, seismographs, seismograms - what's the difference?
---------------------
#Seismographs are instruments used to record the motion of the ground during an earthquake. They are installed in the ground throughout the world and operated as part of a seismographic network. The earliest "seismoscope" was invented by the Chinese philosopher Chang Heng in A.D. 132. This did not, however, record earthquakes; it only indicated that an earthquake was occurring. The first seismograph was developed in 1890.

#Seismometer is the internal part of the seismograph, which may be a pendulum or a mass mounted on a spring; however, it is often used synonymously with "seismograph".

#Seismogram is the recording of the ground shaking at the specific location of the instrument.

Source: USGS
#GeneralKnowledge | What is Richter scale ?
-----------------
The Richter scale is a scale that seismologists use to measure the amount of ground shaking and energy that is released from earthquakes. It was created in 1935 and is highly efficient when measuring earthquakes that are small to medium-sized.


The earthquake's magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by a seismograph.
👍4
Ethiopian Association of Geoscience (EAG)
Updated map of Fentale earthquake Earthquake Hazard Distribution and geological summary included
If you carefully see this map. About 290,000 peoples living within 35 kilometers radius from Mount Fentale.

Now government decided to move 80,000 peoples from 12 Kebeles.

If the magnitude continue to increase, more efforts might be needed!

Indeed, it isn't an easy task. But we have to work hard and off course vigilantly.
This media is not supported in your browser
VIEW IN TELEGRAM
Video showing the damage caused by last night’s earthquake at the Kessem Sugar Factory. All factory more than 1000 staff have been evacuated
Earthquakes can be measured in two ways. One method is based on magnitude—the amount of energy released at the earthquake source. The other is based on intensity—how much the ground shakes at a specific location. 
👍21
#GeneralKnowledge | Earthquake magnitude & intensity with distance from epicenter ?
---------
Earthquake waves diminish in intensity as they travel through the ground, so earthquake shaking is less intense farther from the epicenter.

Low-frequency waves diminish less rapidly with distance than do high-frequency waves.

Therefore, the damage/intensity at the epicenter is higher than farther distance.


That's why the Fentale earthquake doesn't felt equally at Metahara, Adama and Addis Ababa. The same with expected damages.
👍2
Could this lead to the development of a big fissural eruption ? ???
Or multiple vents with fissures ?
Like the 2005 Babbahu volcanic eruption ?
👍2
#GeneralKnowledge | Phreatic Eruption (explosion)
---------
A phreatic eruption is made up of steam-driven explosions that occur when water beneath the ground or on the surface is heated by volcanic activity. The water, once heated, begins to boil or can even flash straight to steam, causing an explosion.

Ejecta include
- steam / Water
- rock fragments


----- Others words ------
Phreatovolcanism
Hydrovolcanism
👍2
A scheme of a phreatic eruption:
1: water-vapor cloud,
2: magma conduit,
3: layers of lava and ash,
4: stratum,
5: water table,
6: explosion,
7: magma chamber
👍2