WHY IN NEWS ?
- Turkey got hit by two large earthquakes of magnitude 7.8 and magnitude 7.5, hitting southeastern part of country.
- Nearly 200 aftershocks have followed with earthquakes of magnitude 6 being reported in the region three days after the first tremblor.
- It had claimed loss of nearly 20000 lives and wreaking considerable damage in Turkey as well as Syria.
CAUSE OF EARTHQUAKES
- As the earth’s crust is made up of roughly 15 massive segmented chunky slabs called tectonic plates which are constantly in motion.
- The land on which buildings are built rests on these plates.
- The plates continually collide, push and grate against each other and the meeting points of these plates are made up of a series of ‘faults.’
- The pent up energy from the nestling plates, along fault lines, is often released when an imbalance in pressure causes rocks on either side of the fault to re-adjust.
- One set of rocks rising up relative to the other is a ‘normal’ fault, while if one sliding down relative to the other is a ‘reverse’ fault.
- But when they grate, or move past one another, it’s a ‘strikeslip.’
- The energy released travels as waves that cause the ground to shake known as earthquake.
MAGNITUDE OF EARTHQUAKE
- The time, location, and magnitude of an earthquake can be determined from the data recorded by seismometer.
- Seismometers record the vibrations from earthquakes that travel through the Earth.
- Each seismometer records the shaking of the ground directly beneath it.
- Magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 is a moderate earthquake, and a 6.3 is a strong earthquake.
- Due to this logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude as measured on a seismogram.
Earthquake Magnitude Scale
|Magnitude||Earthquake Effects||Estimated Number Each Year|
|2.5 or less||Usually not felt, but can be recorded by seismograph.||Millions|
|2.5 to 5.4||Often felt, but only causes minor damage.||500,000|
|5.5 to 6.0||Slight damage to buildings and other structures.||350|
|6.1 to 6.9||May cause a lot of damage in very populated areas.||100|
|7.0 to 7.9||Major earthquake. Serious damage.||10-15|
|8.0 or greater||Great earthquake. Can totally destroy communities near the epicenter.||One every year or two|
GEOLOGY OF SYRIA-TURKEY EARTHQUAKE
- Turkey and Syria lie at the confluence of three plates i.e. the Arabian Plate, the Anatolian Plate and the Eurasian Plate. Thus making the region an extremely seismically active zone.
- The Arabian Plate is inching north into Europe, causing the Anatolian Plate (which Turkey sits on) to be pushed out west.
- The bulk of Turkey sits on the Anatolian Plate between two major faults: the North Anatolian Fault and the East Anatolian Fault.
- Geologists say that the earthquakes were from a ‘strike slip’ which is typical of the earthquakes in the region.
SIMILARITIES TO INDIAN EARTHQUAKES
- The Indian Plate, colliding into the Eurasian plate and tilting upwards, created the Himalayas.
- The most common type of earthquake in the Himalayan region is due to reverse faults because of the compressive forces between the two plates.
- Scientists have longed warned of a massive, overdue earthquake in the Garhwal Kumaon range here because of what is known about the pattern of quakes in the region.
- In the Turkey Syria earthquakes, energy from nearly 300 years of accumulated strain was released this time.
- Lack of enforcement of building codes in Turkey and the timing of the earthquake in the early morning are believed to be the major factors for the death and devastation inflicted.
- Chile, a country with a long history of devastating earthquakes (over 9), is considered to be a model for earthquake preparedness.
- There should be comprehensive building code and a national instrument providing guidelines for regulating the building construction activities in earthquake prone regions.
- Japan’s effective and contextualized Disaster Management System is important for all countries to learn how to stay best prepared for seismic activities.
SOURCE : THE HINDU
SYLLABUS: MAINS, GS1 GEOGRAPHY