Papers by Vineet K Gahalaut
Several evidences show that during the 2004 Sumatra-Andaman earthquake, the rupture in the Andama... more Several evidences show that during the 2004 Sumatra-Andaman earthquake, the rupture in the Andaman region did not extend up to the trench. Consistent with the earthquake processes at several subduction zones of the world, we propose that subducted unconsolidated sediments of Ganga and Brahmaputra rivers on the Indian plate make the shallow portion of the plate boundary interface behave aseismically and hence the rupture remained blind in the Andaman region. We propose that a similar situation exists in the Himalayan region where the subducted sediments of the Indo-Ganga plains under the Outer Himalaya limit the up-dip rupture propagation during great and major earthquakes. In such a case, rupture during great and major earthquakes may not extend up to the surface. Lack of evidence of surface faulting during the past major and great Himalayan earthquakes is consistent with this idea.
Remote Sensing, 2021
The Palghar region (north Maharashtra, India), located in the northwestern part of the stable con... more The Palghar region (north Maharashtra, India), located in the northwestern part of the stable continental region of India, experienced a low magnitude earthquake swarm, which was initiated in September 2018 and is continuing to date (as of October 2021). From December 2018 to December 2020, ~5000 earthquakes with magnitudes from M1.2 to M3.8 occurred in a small region of 20 × 10 km2. These earthquakes were probably triggered by fluid migration during seasonal rainfall. In this study, we have used multi-temporal Landsat satellite data of the year 2000, 2015, 2018, 2019, and 2020, extracted lineaments, and studied the changes in frequency and pattern of lineaments before and after the initiation of the swarm in the Palghar region. An increase in the lineament density and amount of rainfall are found to be associated with the increasing frequency of earthquakes.
Journal of Geophysical Research: Space Physics, 2020
Journal of Earth System Science, 2021
Abstract Sadrabadi and Zilphi villages of Dharni Taluka in Amravati district, Maharashtra, experi... more Abstract Sadrabadi and Zilphi villages of Dharni Taluka in Amravati district, Maharashtra, experienced small magnitude earthquakes between September 1, 2018 and December 9, 2018. We deployed a four station temporary network of three component broadband seismographs to understand and characterize the earthquake sequence. We find that the short lived (~2 months) micro-earthquake ( M ≤ 2.4) swarm, accompanying rumbling sound, was highly clustered (3×3 km 2 ) and occurred at extremely shallow depth (<0.4 km). Analysis of the data reveal that the earthquake swarm might have been induced by the percolation of monsoonal rainwaters (reaching ~100 mm/day) through the cracked volume of soil/rock, associated with the fault system of the Narmada Son failed rift region. Besides revealing the science of earthquake swarm and characterizing it, the monitoring of earthquake swarm and its analysis contributed significantly in reducing the public panic. Highlights We report a case of monsoonal rainfall induced earthquakes from the Narmada Son failed rift region in Amravati district. The earthquake sequence is referred here as an earthquake swarm. The near surface shallow focused micro earthquakes (M≤2.4) occurred in a small region (3×3 km 2 ) immediately after the monsoon of 2018. Monitoring of such sequence is important to declare whether the sequence is a swarm activity that may not lead to the occurrence of a strong earthquake in the region.
Tectonophysics, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Journal of Asian Earth Sciences, 2018
The ~1200 km long north-south oriented Sagaing fault (plate boundary fault between the Burma and ... more The ~1200 km long north-south oriented Sagaing fault (plate boundary fault between the Burma and Sunda plates), entirely located in Myanmar, passes through some major cities, and has witnessed several major earthquakes since prehistoric time, including the recent Mw 6.8 Thabeikkyin earthquake in 2012. The Sagaing fault accommodates ~50-55% of dextral motion of the India-Sunda plate motion. Combined, geodetic observations and rheological considerations using topography as a proxy, we propose along strike segmentation of the Sagaing fault from centrally locked segment to creeping segment further north along the Koma fault. Such segmentation facilitates stress transfer (or loading) from creeping segment to locked segment, and influences earthquake nucleation process and along strike spatial extent of great earthquake ruptures. Topographic margins and their relative strength, predicted from the Newtonian channel flow model, also support the along strike segmentation behaviour.
Tectonophysics, 2019
In the wake of major policy reforms implemented in Myanmar since 2011 , its mobile telecommunicat... more In the wake of major policy reforms implemented in Myanmar since 2011 , its mobile telecommunication network has rapidly expanded resulting in an increase in the number of mobile subscribers, and in the exposure of a large proportion of the population to social media via mobile broadband services. For example, users of social networking portals in Myanmar grew from nearly 1-million active users in January 2014 to more than 10-million active users in 2016, with more than 80% of them accessing social media via their mobile devices (Myanmar Times, 1 April 2016). Tapping this unique resource for the first time in Myanmar, we elicited felt reports for both the M W 6.9 Kani earthquake on 13 April 2016, and the M W 6.8 Chauk earthquake on 24 August 2016 via the Burmese language Facebook portal of the Myanmar Earthquake Committee (MEC). The MEC was founded in 1999 to facilitate research on seismic hazards and earthquake engineering in Myanmar, and to increase the awareness of disaster mitigation and preparedness within the country. We supplemented our field surveys conducted immediately after both earthquakes with these felt reports, as well as news reports from digital versions of conventional newspapers to map the macroseismic intensity distributions for both earthquakes. We then compared our observations to available instrumental records of Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV), and tested the validity of selected Ground Motion to Intensity Conversion Equations (GMICEs) and GMPEs for Myanmar and the surrounding regions. The seismotectonics of Myanmar and the surrounding region are largely controlled by the on-going India-Eurasia collision (Tapponnier
Journal of Asian Earth Sciences, 2019
Pure and Applied Geophysics, 2016
Earthquakes continue to occur in the Kalabsha embayment region near the Aswan reservoir for more ... more Earthquakes continue to occur in the Kalabsha embayment region near the Aswan reservoir for more than three decades. These earthquakes, including the 1981 mainshock (M 5.3), have been considered to be reservoir triggered and pore pressure appears to be the main factor for their occurrence. However, influence of reservoir water levels on the earthquakes of the region, which is significant in the initial period, is reported to be weakening with time. We statistically analyse the influence of the reservoir water levels on spatio-temporal distribution of the earthquakes for the period 1982–2013. We divided the seismicity of various zones in different time windows, depending upon their clustering, and employed the power spectrum and singular spectrum analysis (SSA). The influence of long-term and annual variations in the water level on the seismicity is very much apparent in SSA. In the 45 years of reservoir filling history, episodes of water levels more than 170 m, which lead to filling of the embayment region, appear to be correlated with the increase in seismicity of the Aswan region. In the power spectrum analysis, a strong annual peak is found for water level time series. However, in the earthquake time series, on an average, a moderate and weak annual period cycle is present in the initial (1982–1988) and in the later (2001–2013) period, respectively. In the intermediate period (1989–2000) when the water level was the least in the embayment area, a very weak annual cycle is present. Non-consideration of spatio-temporal variation in the seismicity leads to erroneous and misleading results of no or weaker reservoir influence in the later period. This also highlights that the time and space dependent pore pressure diffusion process is likely responsible for earthquake triggering in the Aswan region.
Journal of Asian Earth Sciences, 2017
We estimate coseismic offsets at 20 sites in India due to the 25 April 2015 Gorkha, Nepal (Mw 7.8... more We estimate coseismic offsets at 20 sites in India due to the 25 April 2015 Gorkha, Nepal (Mw 7.8) earthquake. Only four sites in the Indian region, immediately to the south of the rupture, showed discernible coseismic horizontal offsets ranging between 3 and 7 mm toward north. We invert these offsets along with 13 other offsets at GPS sites in Nepal and 33 offsets at sites in China, for the estimation of slip distribution on the causative rupture. We assume that rupture occurred on the Main Himalayan Thrust (MHT). In our estimated slip model, high slip reaching $5 m occurred east of the mainshock epicenter, and the slip on rupture terminated close to the Main Boundary Thrust (MBT). Thus the rupture for this earthquake remained blind, increasing the potential for future earthquake in the shallow, updip unruptured part of the MHT.
Journal of Asian Earth Sciences, 2012
ABSTRACT A damaging and widely felt moderate earthquake (Mw 6.4) hit the rural, mountainous regio... more ABSTRACT A damaging and widely felt moderate earthquake (Mw 6.4) hit the rural, mountainous region of southwestern Pakistan on October 28, 2008. The main shock was followed by another earthquake of identical magnitude (Mw 6.4) on the next day. The spatial distribution of aftershocks and focal mechanism revealed a NW–SE striking rupture with right-lateral strike-slip motion which is sympathetic to the NNW–SSE striking active mapped Urghargai Fault. The occurrence of strike-slip earthquakes suggests that along with the thrust faults, strike slip faults too are present beneath the fold-and-thrust belt of Sulaiman–Kirthar ranges and accommodates some of the relative motion of the Indian and Eurasian plates.To assess the characteristics of this sequence, the statistical parameters like aftershocks temporal decay, b-value of G–R relationship, partitioning of radiated seismic energy due to aftershocks, and spatial fractal dimension (D-value) have been examined. The b-value is estimated as 1.03 ± 0.42 and suggests the tectonic genesis of the sequence and crustal heterogeneity within rock mass. The low p-value of 0.89 ± 0.07 implies slow decay of aftershocks activity which is probably an evidence for low surface heat flow. A value of spatial fractal dimension of 2.08 ± 0.02 indicates random spatial distribution and that the source is a two-dimensional plane filled-up by fractures.The static coseismic Coulomb stress changes due to the foreshock (Mw 5.3) were found to increase stress by more than 0.04 bars at the hypocenter of the main shock, thus promoting the failure. The cumulative coseismic Coulomb stress changes due to the foreshock and mainshocks suggest that most of the aftershocks occurred in the region of increased Coulomb stress, and to the SE to the mainshock rupture.
The data presented suggest that uplift of the outer Himllaya in this region is continuing even to... more The data presented suggest that uplift of the outer Himllaya in this region is continuing even today through sudden co-seismic elevation changes during large thrust earthquakes and secular aseismic uplift during intervals between such earthquakes. The observed co-seismic ground elevation changes during the Kangra earthquake are interpreted so as to simulate the cross-sectional shape of the buried active thrust fault responsible for this continuing episodie as well as secular uplift of the Outer Himalaya. This fault is assumed to be the surface of detachment between the Himalayan rocks above and the Indian shield rocks below. It is concluded that over most of its extent in Dehra Dun region, the detachment surface has gentle dip to the northeast but a few interspersed, northeast dipping steeper ramps are not ruled out. The depth of the detachment is estimated to be between 0 and 3 km beneath the SW limit and about 10 km beneath the NE limit of the Outer Himalaya in the Dehra Dun region. The two main levelling observations regarding the current inactive status of the Main Boundary Thrust (MBT) are, (1) the involvement of this thrust in the occurrence of the Kangra earthquake is definitely ruled out from the levelling data, and (2) the measured rate of secular uplift of the ground increases from NE to SW across the surface trace of the thrust suggesting that the Outer Himalaya is rising faster than the Lesser Himalaya to the NE across the MBT.
Current Science, 2016
A nation's development and prosperity goes hand in hand with its capacity to generate renewab... more A nation's development and prosperity goes hand in hand with its capacity to generate renewable sources of energy through power generation, which is crucial to balance the depleting natural resources. However, regions with Nuclear Atomic Power Station (NAPS) are often perceived to be infiltrated with toxic emissions percolating in their water reservoirs and atmosphere, which may be detrimental for all life forms in the vicinity. A botanical trip was conducted to NAPS at Narora (Figure 1) while carrying out survey and plant collection of the Upper Ganga Ramsar Site in Uttar Pradesh, India. This riverine Ramsar Site extends along 85 km stretch of the River Ganga beginning at Brij Ghat in Ghaziabad district and ending at Narora in Bulandshahr district, passing through the Budaun and Moradabad districts.
Journal of the Geological Society of India, 2017
Earthquakes in Koyna-Warna region are triggered by the reservoirs but the reasons for sustained s... more Earthquakes in Koyna-Warna region are triggered by the reservoirs but the reasons for sustained seismicity, in terms of magnitude and time, remain enigmatic. We critically review the proposed models/processes, which include fault interaction, flexure of Western Ghat escarpment, velocity heterogeneity, and earthquakes being considered as aftershocks. We suggest that each of these processes or models have limitations and are not capable of explaining all the features of seismicity individually. It is possible that all put together and some other unknown additional processes are at work and there is a mish-mash of several processes attending the region, causing continuing seismicity for past five decades.
Proceedings of the Indian National Science Academy, 2020
We provide a short overview of the seismological research conducted by the Indian researchers per... more We provide a short overview of the seismological research conducted by the Indian researchers pertaining to the Indian subcontinent, during the past five years. This synthesis primarily includes results of studies on crustal architecture, geodynamics, seismotectonics and earthquake source parameters. An appraisal of the earthquake monitoring networks in India is also provided.
Natural Hazards, 2016
We use 21 strong motion recordings from Nepal and India for the 25 April 2015 moment magnitude (M... more We use 21 strong motion recordings from Nepal and India for the 25 April 2015 moment magnitude (M W) 7.8 Gorkha, Nepal, earthquake together with the extensive macroseismic intensity data set presented by Martin et al. (Seism Res Lett 87:957-962, 2015) to analyse the distribution of ground motions at near-field and regional distances. We show that the data are consistent with the instrumental peak ground acceleration (PGA) versus macroseismic intensity relationship developed by Worden et al. (Bull Seism Soc Am 102:204-221, 2012), and use this relationship to estimate peak ground acceleration from intensities (PGA EMS). For nearest-fault distances (R RUP \ 200 km), PGA EMS is Electronic supplementary material The online version of this article (
Journal of Asian Earth Sciences, 2012
ABSTRACT An overview of seismicity along the northwest Himalaya exhibit along-strike segmentation... more ABSTRACT An overview of seismicity along the northwest Himalaya exhibit along-strike segmentation intricately controlled by the subsurface topographic ridges on the underthrusting Indian Plate as well by rift and nappe structures in the overriding wedge of the Himalaya. The segmentation exists for thrust dominated large magnitude earthquakes (M &amp;gt; 6) seated on the active detachment beneath the Outer and Lesser Himalaya. Segmentation also prevails for moderate and small magnitude earthquakes concentrated in a narrow Himalaya Seismic Belt (HSB) straddling northern Lesser Himalaya and southern Higher Himalaya. Numerical calculations of stress distribution favour that the degree of seismicity in the HSB is a good proxy to the presence of mid-crustal ramp connecting the locked section of active detachment to aseismically slipping detachment beneath Higher Himalaya. Further, gap or diffused pattern in the concentrated seismicity in the HSB, in agreement with mapped high electrical conductive structure, suggests ramp structure may be absent where underthrusting Delhi-Hardwar Ridge interacts with the Himalaya arc. In the nappe dominated tectonics, the accommodation of the accumulating strains on the listric thrust faults, produces increased frequency of moderate magnitude earthquakes and thereby possibly influences stress level on the detachment. This may explain relatively less frequent occurrences of large earthquake in the Kangra–Chamba region compared to that in the Garhwal Himalaya. The low level seismicity in the Simla region may also be influenced by the active Kaurik Chango Rift in the Higher Himalaya, as the former casts a stress shadow on the latter.
Gondwana Research, 2014
Bounded by the western and eastern syntaxes, the Himalayan region has experienced at least five M... more Bounded by the western and eastern syntaxes, the Himalayan region has experienced at least five M~8 earthquakes during a seismically very active phase from 1897 through 1952. However, there has been a paucity of M~8 earthquakes since 1952. Examining of various catalogues and seismograms from the Gottingen Observatory, it is established that this quiescence of M~8 earthquakes is real. While it has not been possible to forecast earthquakes, there has been a success in making a medium term forecast of an M 7.3 earthquake in the adjoining Indo-Burmese arc. Similarly we find that in the central Himalayan region, earthquakes of M > 6.5 have been preceded by seismic swarms and quiescences. In the recent past, based on GPS data, estimates have been made of the accumulated strains and it is postulated that a number of M~8 earthquakes are imminent in the Himalayan region. We examine these estimates and find that while earthquakes of M~8 may occur in the region, however, the available GPS data and their interpretation do not necessarily suggest their size and time of occurrence and whether an earthquake in a particular segment will occur sooner in comparison to that in the neighboring segment. We also comment on the inference of occurrence of M~8 earthquakes based on M8 algorithm for the region. We conclude that while an M~8 earthquake could occur any time anywhere in the Himalayan region, there is no indication as of now as to where and when it would occur. We impress on the need for preparedness to mitigate the pending earthquake disaster in the region.
GPS RINEX data set from Indian sub-continent and Southease Asia during the Decemeber 26, 2019 ann... more GPS RINEX data set from Indian sub-continent and Southease Asia during the Decemeber 26, 2019 annular solar eclipse and the day before it.
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Papers by Vineet K Gahalaut