Seismology and Geosciences
Under the Seismology and Geosciences (SAGE) scheme of the Ministry of Earth Sciences (MoES), several important programmes and activities are under implementation by MoES with its network of institutions.
SAGE includes the following six activities:
- Seismological monitoring and microzonation
- Geodynamics and surface processes
- Indian Ocean: deep ocean observations and dynamics of lithospheric evolution (International Ocean Discovery Program-IODP and geoid low)
- Scientific deep drilling in the Koynaintraplate seismic zone
- Seismicity and earthquake precursors
- Setting up a facility for geochronology
1. Seismological monitoring and microzonation
The National Centre for Seismology (NCS) in New Delhi is an attached office of MoES. It operates and maintains the NSN or the National Seismological Network. NSN consists of 115 seismological observatories spread across the country.
NCS maintains a round-the-clock watch of seismic activity in the country. A Central Receiving Station (CRS) at NCS receives real-time digital waveform data from field stations. This data is used to determine preliminary earthquake source parameters. Whenever an earthquake occurs in the country, its information is immediately disseminated to a variety of user agencies, including disaster management authorities. NCS shares this information via earthquake bulletins within five minutes of an earthquake. It is also involved in the monitoring of aftershock and swarm activity if occurred, throughout the country.
NSN is capable of recording earthquakes/events of magnitude (M)≥2.5 in and around Delhi, M≥3.0 for North East (NE) region, M≥3.5 in the peninsular and extra-peninsular areas, and M≥4.0 in border regions. The plan is to add 35 more seismic stations in next 1-2 years, and nearly 300 seismic stations in next five or so years. This will increase the capability of detecting earthquakes up to M 2.5 throughout the country. It will also enhance location capabilities for earthquake mitigation efforts.
Another important activity implemented by the NCS is microzonation. It is a site-specific study that provides a more realistic and reliable representation of ground motion characteristics. It involves sub-division of a region into zones that have relatively similar exposure to various earthquake-related effects. This exercise is similar to the macro-level hazard evaluation. Still, it requires detailed inputs on site-specific geological conditions, ground responses to earthquake motions and their impact on the safety of constructions. It is useful in land use and urban planning and also in retrofitting of the existing buildings. MoES has recently completed Seismic Microzonation of Delhi and Kolkata. Copies of these reports have been shared with stakeholders at the State and Centre.
Seismic microzonation of a few other areas such as Sikkim, Guwahati, and Bengaluru has also been done in a project mode. Work at four more cities (Bhubaneswar, Chennai, Coimbatore and Mangalore) is at an advanced stage of completion. Microzonation task at eight more cities (Patna, Meerut, Amritsar, Agra, Varanasi, Lucknow, Kanpur and Dhanbad) is being initiated. Earthquake hazard assessment and microzonation studies are planned to be undertaken in seismically vulnerable areas of the country in a phased manner.
2. Geodynamics and surface processes
This program addresses the modelling of crustal, coastal, geohydrological and atmospheric processes to assess wave climate, hydrodynamics and sediment transport along selected stretches of the Indian west coast. It aims to understand the impact of coastal structures.
Research under this program is categorized under the following four themes
- Crustal processes: It includes studies related to deep internal processes during the Earth’s history; cover sequences in the form of sedimentary deposits and surface processes and neo/active tectonics relative to the present-day seismicity and land distribution the Western Ghats.
- Coastal processes: It includes studies of beach morphodynamics and nearshore sediment transport, modelling of coastal processes and coastal, estuarine and inner shelf sedimentation.
- Natural resources and environmental management: It includes studies on critical zone characteristics of selected watersheds of Indian rivers, evaluation of hydrological and biogeochemical aspects of peninsular river basins and generation of geo-environmental inputs for natural resources management planning and development activities.
- Natural Hazard: It addresses natural hazards such as landslides including land subsidence, earthquake, flood, drought, coastal erosion, lightning, sea-level rise, storm surge and tsunami inundation in the Western Ghats region.
The National Centre for Earth Science Studies (NCESS), Thiruvananthapuram, implements the core R&D under this program. It will also investigate the quaternary climate and sea-level variability of Indian west coast towards predicting future climate and sea-level changes in the Indian sub-continent. NCESS is setting up critical zone observatories in peninsular India. The aim is to understand the chemical, physical, geological, and biological processes that shape the surface of Earth and support terrestrial life.
A national network project called Submarine Groundwater Discharge (SGD) is also being implemented under this program. It will help to quantify the amount of fresh groundwater discharge into the Bay of Bengal and Arabian Sea through coastal aquifers. Such discharge is an important pathway for nutrients, carbon and other geochemical constituents to the ocean. It has been recognized to ecologically significant despite being volumetrically small. Knowledge of the nature of SGD allows scientists to estimate optimum extraction levels of potable groundwater and provide information on feasible waste disposal sites in coastal zones. SGD is temporally and spatially variable, as the interaction between multiple forcing mechanisms varies at any given location and time. Therefore, a site-specific investigation to evaluate the timing, magnitude, and importance of SGD in any interface zone between salt water and fresh water is essential.
3. Indian Ocean: Deep ocean observations and dynamics of lithospheric evolution (IODP and geoid low)
The MoES joined the International Ocean Discovery Program (IODP) consortium in 2009 as an Associate Member through an MoU with National Space Foundation, USA. Since joining the IODP consortium, Indian scientists have been participating in IODP expeditions each year for scientific research in different facets of scientific drilling in a variety of geological settings around the world. Taking the lead, in 2015, India undertook an exclusive drilling expedition,IODP-355,in the Arabian Sea to collect long sediment cores for unravelling the long-term evolution of Indian Monsoon and its linkages with the mountain building process in the Himalaya. During the expedition, two boreholes were drilled in the Laxmi Basin, eastern Arabian sea, Indian ocean with the help of the research vessel JOIDES Resolution. In total, ~1700m of sediment and sedimentary rock, as well as 17m of the igneous basement was drilled. IODP-355 expedition in the Arabian sea has also enabled scientists to discover how a short-lived subduction event around 70 million years ago played a key role in shaping the present-day western Indian continental margin. National Centre for Polar and Ocean Research (NCPOR), Goa serves as the nodal office for IODP-India.
A geoid is a hypothetical equipotential surface that explains the geometrical irregularities of the Earth. It approximates to the mean sea level. Deviations of the geoid from an idealized hydrostatic ellipsoid are known as geoid anomalies. The uneven mass distribution in the Earth’s interior is predominantly attributed to the geoid variations from place to place in terms of highs (positive) and lows (negative). The Indian Ocean Geoid Low (IOGL), centred near to south of Sri Lanka, is the largest geoid low in the globe. Under this program, it is planned to achieve a comprehensive understanding about the nature, source and cause of the geoid anomalies in the region through integrated interpretation and to develop a better understanding about the geodynamic evolutionary history, mantle processes, etc. To achieve these objectives, NCPOR would acquire various marine geophysical data which includes multichannel seismic data, wide-angle seismic data, deep ocean seismological data, etc. Recently, 17 Ocean Bottom Seismometers (OBS)were deployed in the Indian Ocean. The array recorded continuous, good quality, marine seismological data for more than two years. These data would be used to image the Earth’s mantle structure. It is planned to improve the resolution of the subsurface image for understanding the IOGL anomalies in a better way by deploying a dense OBS array in the near future.
4. Scientific deep drilling in the Koynaintraplate seismic zone, Maharashtra
A programme on scientific deep drilling in the Koynaintraplate seismic zone, Maharashtra has been launched by MoES to understand the mechanism of recurrent earthquakes in the Koyna region. A unique approach has been adopted to address this question. Deep boreholes will be drilled till the depthat which earthquakes originate. Then a deep borehole observatory will be set up. It will facilitate direct observations of physical and mechanical properties of rocks, pore fluid pressure, temperature and other parameters of an intra-plate, active, fault zone in the near-field of earthquakes–before, during and after their occurrence. It would provide valuable information to address the issue of frequent earthquakes in the Koyna region.
The preparatory phase of the programme was carried out in2012-2014 in association with CSIR-National Geophysical Research Institute, Hyderabad. It comprised of drilling shallow exploratory boreholes at nine sites in the Koyna-Warna region, and geophysical well logging. This was followed by studies on heat flow, magnetotelluric sounding (at hundred stations), deep resistivity, controlled source audio-frequency, low elevation airborne gravity gradiometry and magnetism (5012 line km), airborne LiDAR (Light Detection and Ranging)covering an area of 1,064 square kilometres, and seismology.
To implement the deep drilling phase and to set up the deep borehole observatory, Borehole Geophysics Research Laboratory (BGRL) was set up in October 2014 at Karad, Maharashtra. BGRL has undertaken to develop indigenous capacity and expertise in all aspects of scientific drilling, deep borehole geophysics, associated geological investigations and modelling dedicated to earthquake research. Laboratory facilities for advanced experimentation in rock mechanics, petrology, geothermal and other geological studies are planned to complement the in-situ studies.
Deep drilling up to ~7 km and setting up of the proposed fault zone observatory to measure co-seismic changes in physical and chemical properties at hypocentral depth requires apriori knowledge of rock properties and fault zone parameters in the Koyna region. To obtain these parameters, a pilot borehole was drilled to 3 km depth in the seismogenic zone for downhole geophysical measurements and possible seismic monitoring. The studies carried out so far have provided new insights into the recurrent low magnitude earthquakes from geological, geothermal and geomechanical perspectives. They have also yielded valuable inputs for further deep drilling and design of a deep borehole observatory in the region.
5. Seismicity and earthquake precursors
It is a research-driven programme with a perspective to provide impetus to the studies related to seismology, which provides thrust to the earthquake‐related studies and also to generate inputs for earthquake disaster mitigation. It aims to generate long‐term and comprehensive multi‐parametric geophysical observations in seismically active areas, towards establishing possible relationships between earthquake precursory phenomenon and the earthquake generation processes.
In this direction, Multi-Parametric Geophysical Observatories (MPGOs) were established at selected sites namely, Ghuttu, Garhwal Himalaya and two in NE region at Tezpur and Imphal. Also, specific R&D on various aspects of seismology and earthquake engineering, such as delineation of geological structures, monitoring of local faults, study of slow earthquakes, rupture propagation, attenuation studies, site characterization, simulation of ground motion and liquefaction investigations were carried out by individual researchers in project mode in selected areas. These studieshave helped tounderst and seismogenesis, seismotectonics, and conduct an assessment of seismic hazard and design of structures. In addition, over 60 Global Positioning Systems (GPS) and 50 broadband (BB) seismometers, have been established in project mode in the country with specific objectives.
Recognising the importance of active tectonics, a dedicated programme was initiated to undertake active fault mapping of the country in a systematic and comprehensive manner. This programme aims at defining and categorizing the active faults of India, generating composite datasets and ensuring their availability to the users in a GIS compatible format and preparing active fault maps of different regions and the country. Four areas, namely, North-West and Central Himalaya, Kashmir Himalaya, North-East Himalaya and Kachchh have been selected as priority areas to begin work. A base document for active fault mapping has been prepared, which provides a detailed explanation of the methodologies and techniques available for systematic active fault mapping/studies. First cut (preliminary) active fault map for NW & central Himalaya and Kachchh region on 1:25000 scale have been prepared. Most of the R&D activity under this program is mapped to the REACHOUT scheme under PAMC-Seismology. However, two important activities, namely, earthquake precursory research and active fault mapping program are being implemented under the SAGE scheme.
6. Setting up a facility for geochronology
In the past few decades, the field of geosciences has witnessed a paradigm shift from being an observational science to a more rigorous multidisciplinary subject with a robust quantitative database. The field has seen new developments in geochronology at the micro phase and single-grain levels.
Geochronology is the study of the age of rocks, fossils and sediments. It seeks to answer several perplexing scientific questions. Modern research has established that isotopic composition (stable and radiogenic) of geological material is essential to understand geological processes in time and space, that is, for studying geochronology.
High precision isotopic measurements require equally sophisticated instrumentation and laboratory infrastructure. India is in the process of developing such facilities. MoES is setting up ageochronology facility at Inter University Accelerator Centre (IUAC), New Delhi to cater to the need of geoscientists of the country. The geochronology facility has the mandate of developing an internationally-competitive centre for geochronology and isotope geochemistry that will facilitate generation of quality isotopic data for geochronological and isotopic fingerprinting.
IUAC would enable geoscientists to undertake cutting-edge research with high-quality data and its characterization at the highest international level. It will provide high-end experimental capabilities which are currently non-existent in the country. More facilities to complement the existing infrastructure will be added going forward. IUAC will have two major machines, namely, an Accelerator Mass Spectrometry (AMS) and High-Resolution Secondary Ionization Mass Spectrometry (HR-SIMS). A variety of ancillary equipment capable of dating geologically youngest and the old formations/rocks/sediments in the Earth’s history will also be present. IUAC would facilitate an improved and quantitative understanding of the evolution of the Indian lithosphere.
Accelerator Mass Spectrometry (AMS) will attempt to address questions around erosion rates, dating of seismic events, sediment provenance, quantitative Earth surface processing studies, etc. Establishment of AMS dating facility will also provide a means to explore new isotopes like 32Silicon, 36Chlorine, 41Calcium. AMS dating data has potential applications in hydrology, glaciology and ocean circulation studies.
The High-Resolution Secondary Ionization Mass Spectrometry (HR-SIMS) will provide data for dating of elements such as zircon, and accessory minerals such as monazite, titanite, sphene and apatite at a high spatial resolution. HR-SIMS has been recently established at IUAC, New Delhi and will aid scientists to decipher complex growth histories in processes that led to Earth’s crust formation and continental dynamics. It will also help in conducting elaborate isotopic analyses in deep earth processes and those related to cosmochemistry.HR-SIMS has been installed at a facility in Delhi and would be operational very soon.