Exploring the origin of the largest Geoid low on the Earth


a) Objective:

To study the nature and origin of the geoidal low in the Indian Ocean centered around south of Sri Lanka.

Justification: Geoid is an equipotential surface of the Earth’s gravity fields that best fits the global mean sea level in a least squares sense. Recent gravity models and satellite based observations show that geoid rises and falls over spheroid as much as-100 m to +100 m. The undulations in geoid are caused due to subsurface density heterogeneities and long wavelength geoid anomalies are often interpreted as present-day mantle density heterogeneities. These have a direct bearing on the physical and chemical properties of deep mantle and processes that are responsible for phenomena such as mantle convection, plate tectonics etc. Thus elucidating large wavelength Geoid anomalies is of significance in global geodynamical studies.

Despite the significance of the gravity low in the context of global geodynamics, no systematic study of this anomaly has been undertaken. The available seismic stations in the vicinity are few and far between and there are no ocean bottom observatories (OBOs) in the area. Ray paths are scanty, particularly over central low.

b) Implementation Plan:

It is proposed to deploy two kinds of seismic arrays over this low, along with global seismic network (like IRIS): one along a North-South line, over Chagos-Laccadive, Sri Lanka and southern India, and another array along a line orthogonal to it. Along this latter line of 2500 to 3000km, it is proposed to deploy OBOs at every 100-200 km. The OBOs in the eastern part can also provide additional information about Andaman-Sumatra subduction zone.

c) Budget requirement : 54 Crores

Budget Requirement
Name of the Scheme 2012-13 2013-14 2014-15 2015-16 2016-17 Total
Exploring the origin of the largest Geoid low on the Earth 20.00 20.00 7.00 4.00 3.00 54.00


Last Updated On 04/06/2015 - 17:55
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