The Indian Tsunami Early Warning System situated at Indian National Center for Ocean Information Services, Hyderabad, India, monitors real-time earthquake activity throughout the Indian Ocean to evaluate potential tsunamigenic earthquakes. The functions of the Indian Tsunami Early Warning System earthquake monitoring system include detection, location and determination of the magnitude of potentially tsunamigenic earthquakes occurring in the Indian Ocean. The real-time seismic monitoring network comprises 17 broadband Indian seismic stations transmitting real-time earthquake data through VSAT communication to the central receiving stations located at the Indian Meteorological Department, New Delhi, and the Indian National Center for Ocean Information Services, Hyderabad, simultaneously for processing and interpretation. In addition to this, earthquake data from around 300 global seismic stations are also received at the Indian National Center for Ocean Information Services in near-real-time. Most of these data are provided by IRIS Global Seismographic Network and GEOFON Extended Virtual Network through Internet. The Indian National Center for Ocean Information Services uses SeisComP3 software for auto-location of earthquake parameters (location, magnitude, focal depth and origin time). All earthquakes of Mw >5.0 are auto-located within 5–10 minutes of the occurrence of the earthquake. Since its inception in October 2007 to date, the warning centre has monitored and reported 55 tsunamigenic earthquakes (under-sea and near coast earthquakes of magnitude ⩾6.5) in the Indian Ocean region. Comparison of the earthquake parameters (elapsed time, magnitude, focal depth and location) estimated by the Indian Tsunami Early Warning System with the US Geological Survey suggests that the Indian Tsunami Early Warning System is performing well and has achieved the target set up by the Intergovernmental Oceanographic Commission.

The 2004 Indian Ocean tsunami resulted in catastrophic losses of life and property and demonstrated how destructive the tsunamis can be. In India, the tsunami took away nearly 16,000 lives of the people living in the coastal areas and caused lot of damage to the property. The reason for such a great loss to lives and property is due to lack of awareness and preparedness to tsunamis. Keeping this in view and to avoid further future losses, the Government of India has established the Indian Tsunami Early Warning System at INCOIS, Hyderabad under the Ministry of Earth Sciences. While a tsunami cannot be prevented, its impact can be mitigated through community and emergency preparedness, timely warnings, effective response, and public education. The Tsunami drills evaluates the ability of warning centre and disaster offices to respond to a tsunami. The drills not only emphasize the testing of communications from warning centre to its stakeholders, but also provide an opportunity for testing national/state/local chains of command and decision-making, including the alerting and evacuation of people from selected coastal communities

The Sumatra earthquake of December 26, 2004 generated a tsunami that affected most of the Indian Ocean rim countries. The tsunami caused catastrophic losses of life and property in near field and the far field regions, such as Somalia. Although people living at the coast near the epicenter of the earthquake had little time to escape , those living farther along the coasts of Sri Lanka, India, Maldives and the countries on the east coast of Africa had time to move to the higher grounds to protect themselves. Unfortunately , the loss was inevitable as there was no tsunami warning system in place in the Indian Ocean. The overall loss made this event a prime educator for the people around the world about the hazardous tsunami and highlighted a global failure in mitigating such disaster .

A minor tsunami of about 50 cm was generated along the coast of Qurayat near Makran subduction zone in the Arabian Sea due to the 24 September 2013 Pakistan earthquake of magnitude 7.6 Mw(mB),although its source was ~200 km far inland of the Makran trench. The real time sea level observation network in the Arabian Sea recorded minor tsunami arrivals. In an attempt to explain the mechanism of this unusual tsunami, we use backward ray tracing technique to map the admissible region of tsunamigenic source. Basically, in this technique the ray equations are integrated starting from the specific locations of tsunami observations, in all possible directions. The known travel time of the initial waves to the respective tide gauges and tsunami buoys is used in this method. Backward wave front is constructed by joining all endpoints of the rays from each of the locations. The region where the envelope of all backward wave fronts converges is considered as the source of the tsunami, which is ~470 km from the earthquake epicentre with the location at 24.8 N and 61.5E. The admissible region identified is an undersea section between Chabahar and Gwadar, where a mud island had appeared subsequent to this earthquake. Convergence of the tsunami source zone and location of the mud island suggest that the sudden uplift must have caused the tsunami

The Indian Tsunami Early Warning System (ITEWS) at the Indian National Centre for Ocean Information Services, Hyderabad, is responsible for issuing tsunami bulletins in India. The tsunami centre operates on a 24 x 7 basis and monitors seismological stations, bottom pressure recorders and tidal stations throughout the Indian Ocean to evaluate potentially tsunamigenic earthquakes and disseminating tsunami bulletins. The end-to-end capabilities of this warning system have been well proven during all the tsunamigenic earthquakes that occurred since September 2007. Comparison of the earthquake parameters estimated by ITEWS with other international seismological agencies suggests that the system is performing well and has achieved the target set up by the Inter-governmental Oceanographic Commission.

The Indian Tsunami Early Warning Centre (ITEWC) in Hyderabad monitored the 11 April 2012 tsunami off the coast of Sumatra, which was generated by a shallow strike-slip earthquake and it largest aftershock of magnitude Mw (mB) 8.5 and 8.2 respectively, that occurred inside the subducting slab of the Indian plate. The earthquake generated a small ocean-wide tsunami that has been recorded by various tide gauges and tsunami buoys located in the Indian Ocean region. ITEWC detected the earthquake within 3 min 52 s and issued six advisories (bulletins) according to its Standard Operating Procedure. The ITEWC performed well during the event, and avoided false alarms and unnecessary public evacuations, especially in the mainland part of India region.

Lithospheric thickness is an important parameter to understand the nature of collision and subduction between the Indian and Asian tectonic plates. In this study, we apply the S receiver function technique to data from a network of broad-band stations in the northeast India and Eastern Himalayan regions and image the geometry of Indian Plate collision. This analysis reveals clear S-to-p conversions from the Moho and Lithosphere-Asthenosphere boundary (LAB) in the various tectonic units of the study region. The Indian lithosphere is found to be only 90 km thick beneath the Shillong plateau deepening to 135 km on either side suggestive of a lithospheric upwarp related to the plateau uplift. The lithosphere thickens northward, with values reaching similar to 180 km beneath the Eastern Himalaya. The trend of the LAB north of the foredeep region indicates that the Indian Plate plunges beneath the Eastern Himalaya. The consistent northward-dipping character of the Indian Plate suggests that the Indian Plate is traceable until it gets subducted beneath Tibet just south of Bangong suture zone. The deepening of the LAB and its correlation with the topographic elevation is in agreement with homogeneous thickening of the lithosphere in response to compressive forces due to the continental collision of India with Asia.

In North East India, reliable estimation of earthquake focal depths has always been a problem, owing to paucity of permanent regional seismic stations, constraints on good quality data and lack of crustal models in a complex tectonic terrane. The depth estimations by international agencies, mostly based on teleseismic data, vary from very shallow to even 60 km, suggestive of earthquake occurrence in the upper mantle region. However, modelling of sPn phases in earthquake waveforms that are highly sensitive to focal depths indicates that the earthquake locations are probably well within the crustal layer. The current method has the advantage that dt, the travel time difference between sPn and Pn, remains constant for a wide range of source-station distances, and hence enables easy identification of the sPn phase, while providing direct and accurate estimate of the focal depth. The approach is also insensitive to location errors and variations in crustal models, a useful feature especially while dealing with sparse data with high location errors. In the present study, earthquakes in the magnitude range 3.0-4.0 recorded by a network of nine broadband stations in NE India have been analysed. Consistent dt values at different stations were observed for each event, enabling precise depth estimation mostly within +/- 1 or 2 km. In general, depths of 15-20 km in the Shillong plateau region, > 20 km in the Sylhet basin region and shallow < 10 km in the eastern Himalayan foothills are confirmed, that correlate well with the local tectonics. Further, we propose that the flat characteristics of the dt curve that begin to change for earthquakes below the Moho, can be a potential tool for discriminating between crustal and sub-crustal earthquakes, as well as for delineation of the Moho using dense regional seismic networks in future.

Images of the crust and mantle beneath northeast India obtained by 2D migration of ∼1000 broadband P‐receiver functions clearly trace a northward dipping Moho from the Himalayan foredeep reaching depths up to 50 km further north beneath the Himalayan convergence zone. Also, these images reveal presence of largely coherent 410‐km and 660‐km discontinuities that conform to the IASP91 model. Marginal variations in the depth of the 410‐km interface are observed, that appear region specific. The thickness of the mantle transition zone does not deviate significantly from a global average of ∼250 km. Interestingly, our results reveal consistent presence of a signal from an interface around 300 km. Origin of such a boundary, known as X‐discontinuity and unrelated to the Lehmann discontinuity, is discussed. Possible presence of the X‐discontinuity from the Indian region is reported here for the first time.

Teleseismic receiver functions from a ten station network deployed in northeast India region sampling the Shillong plateau, Mikir Hills, Himalayan foredeep and the Himalayan convergence zone, are analyzed to obtain the crustal structure in this seismically active but less studied region. The Shillong plateau and Mikir hills, away from the convergent margins, reveal remarkably simple crust with thickness (∼35 km) and Poisson's ratio (∼0.25), akin to the Indian shield values. A surprisingly thin crust for the uplifted Shillong plateau may be explained invoking presence of an uncompensated crust that popped up in response to tectonic forces. In contrast, crustal signatures from Assam valley suggest a thicker crust and higher Poisson's ratio with evidences for a dipping Moho. Predictably, the crust is much thicker and complicated in the eastern Himalaya further north, with values in excess of 50 km.