NISAR
SATELLITE AND SEISMIC ZONES - GEOGRAPHY
News:
NISAR satellite to map
Himalayas’ seismic zones
What's
in the news?
●
A forthcoming satellite, NISAR will map
the most earthquake-prone regions in the Himalayas with unprecedented
regularity.
About
the mapping:
●
The data this will generate can
potentially give advance warning of land subsidence, as recently observed in
Joshimath, Uttarakhand, as well point to places that are at greatest risk from
earthquakes.
●
The NISAR satellite will use two frequency bands: the L-band and S-band
to image the seismically active Himalayan region that will, every 12 days,
create a “deformation map”.
●
The geoscience community can use this to
determine how strain is building up in various parts of the Himalayas.
●
These two frequency bands will together provide high-resolution, all-weather data
from the satellite that is expected to follow a sun-synchronous orbit and will
be launched in January 2024.
About
the Himalayan strain:
●
Strain refers to the deformation that occurs in rocks when it is under pressure from
other rocks, usually due to movements of continental plates that are sliding,
colliding, or subducting against each other.
●
The Indian Plate, for instance, collided
into the Eurasian plate forming the Himalayas and continues to incrementally
push it upwards.
Strain
map:
●
Scientists
from the Geological Survey of India in 2021 published a “strain map” of the
Himalayas based on data from 1,252 GPS stations along the Himalayas.
●
It identified regions that had the greatest
odds of generating earthquakes of magnitude above 8 and their extent.
●
With
a frequency of 12 days and the ability to be able to
provide images even under cloudy conditions, NISAR would be a valuable tool to
study deformation patterns, such as in Joshimath.
●
Based on the intensity of past
earthquakes, the knowledge of the speed at which plates move and the locations
at which plates interact (called faults) can help geologists and seismologists
map out regions that are most vulnerable to earthquakes and estimate how far
the resultant tremors can spread.
●
Ground-based observatories can pick up
underground waves that result from an earthquake and provide early warning.
●
Uttarakhand
case: Land subsidence or the loosening of the sub-surface
had caused several parts of Uttarakhand to “sink” and this caused water to seep
via cracks and crevices into houses.
○
In 2021, a large landslide of rock and ice
triggered a flash flood in Chamoli, Uttarakhand that claimed close to 200 lives
and destroyed two hydropower projects. It was satellite imagery that helped
scientists decipher the cause of the flash floods.
About
NISAR mission:
Developed
by: National
Aeronautics and Space Administration (NASA)
and the Indian Space Research Organisation (ISRO).
Launch:
●
It is expected to be launched in January
2024 from Satish Dhawan Space Centre into a near-polar orbit.
Features:
●
The satellite will operate for a minimum of three years.
●
It is a Low Earth Orbit (LEO) observatory.
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NISAR will map the entire globe in 12 days.
●
The 2,800kilogram satellite is a
dual-frequency imaging radar satellite.
●
While NASA
has provided the L-band radar, GPS, a high-capacity solid-state recorder to
store data, and a payload data subsystem, ISRO
has provided the S-band radar, the GSLV launch system and spacecraft.
●
Another important component of the
satellite is its large 39-foot stationary antenna reflector.
●
The reflector will be used to focus “the
radar signals emitted and received by the upward-facing feed on the instrument
structure.
Objectives:
●
Synthetic
Aperture Radar mission is to determine Earth change in three disciplines:
○
Ecosystems (vegetation and the carbon
cycle).
○
Deformation (solid Earth studies).
○
Cryosphere sciences (primarily as related
to climatic drivers and effects on sea level).
Seismic
zone mapping:
●
Over 59
% of India’s land area is under threat of moderate to severe earthquakes.
●
The Bureau of Indian Standards, based on
the past seismic history, divided the country into four seismic zones, viz. Zone II, III, IV and V.
●
The zones are divided on the basis of
Modified Mercalli (MM) intensity, which measures the impact of earthquakes.
Types
of seismic zones:
1.
Zone II:
●
This is seismically the least active region. It covers parts of India that
are not included in Zone III, IV and V.
2.
Zone III:
●
Comprises Kerala, Goa, Lakshadweep
islands, remaining parts of Uttar Pradesh, Gujarat and West Bengal, Parts of
Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra,
Orissa, Andhra Pradesh, Tamil Nadu and Karnataka.
3.
Zone IV:
●
It covers parts of Jammu and Kashmir and
Himachal Pradesh, National Capital Territory (NCT) of Delhi, Sikkim, Northern
parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat and small
portions of Maharashtra near the west coast and Rajasthan.
4.
Zone V:
●
This is seismically the most active region. Parts of the Himalayan boundary
in North and Northeast India fall in this zone.
●
The Kutch area in the West also falls
here. Remaining parts of Jammu and Kashmir, Himachal Pradesh, Uttaranchal, part
of North Bihar and Andaman and the Nicobar Islands are included.