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News Article | April 17, 2017
Site: news.yahoo.com

Sri Lankan army rescuers remove debris from a buried house following a garbage mound collapse in Meetotamulla, on the outskirts of Colombo, Sri Lanka, Colombo, Sri Lanka, Monday, April 17, 2017. Rescuers on Monday were digging through heaps of mud and trash that collapsed onto a clutch of homes near a garbage dump outside Sri Lanka's capital, killing dozens and possibly burying dozens more. (AP Photo/Eranga Jayawardena) MEETOTAMULLA, Sri Lanka (AP) — Rescuers on Monday were digging through heaps of mud and trash that collapsed onto a clutch of homes near a garbage dump outside Sri Lanka's capital, killing at least 30 people and possibly burying dozens more. Hundreds of people had been living in the working-class neighborhood on the fringe of the towering dump in Meetotamulla, a town near Colombo, when a huge mound collapsed Friday night during a celebration for the local new year, damaging at least 150 homes. By Monday morning, authorities had pulled the bodies from beneath the debris, according to a Disaster Management Center report. Authorities were unsure how many more people could still be trapped, with contradictory reports being released. They announced 30 people were missing Monday but later reduced the number to 11. Disaster Management Center spokesman Pradeep Kodippili said the number was reduced after adjusting names that had been entered on the list of dead as well as missing. Law and Order Minister Sagala Ratnayake said the number of people could be between six and 10. Soldiers were digging with backhoes and shovels, as relatives of the missing pointed out where their houses once stood amid coconut, mango and banana trees. Those homes now lay in piles of collapsed concrete walls encased in a wall of mud up to 8 meters (25 feet) high and mixed with plastic bags, broken glass and other trash. Bicycles and auto-rickshaws, the three-wheeled vehicles used as local taxis, were crushed or lying topsy-turvy. In other parts of the dump officials were mapping places that can slide and identifying families that need to be evacuated. More than 600 of the area's residents were sheltering in nearby schools, while 11 people were being treated at a hospital for injuries. One auto-rickshaw driver described a narrow escape. He was returning home with his wife, two sons and daughter when they stepped out from his rickshaw and his daughter said the ground seemed to be moving beneath her feet. "There was a strong wind from the side of the dump, and my daughter shouted that the mound is splitting," Rasika Sanjeewa, 41, said Monday. "Suddenly, one slice of the mound came crashing down. The whole area was shaking." Debris blocked them from fleeing immediately, but eventually they found a way out, Sanjeewa said. When they arrived later at their friends' home, where they had planned to celebrate the new year, they found it buried and their friends dead — a mother and daughter who worked as daily wage laborers. The prime minister vowed over the weekend to shut down the dump, which has absorbed much of Colombo's garbage over several years amid heavy construction and renovations in the capital. As the garbage piled up, it began threatening the nearby homes, prompting residents to stage regular protests while complaining of health hazards. "These people did not choose to live next to a dump. But they brought the garbage in and made this place horrible," said rickshaw driver Dilip Mirmal, 34, whose home was spared while those surrounding were completely subsumed. He counted 23 of his neighbors among the dead. "This is a government-made disaster," he said. "I have a mix of feelings — of anger, frustration and sorrow. We have been trying to protest and raise these issues, but no one was listening."

Padhy S.,National Geophysical Research Institute | Padhy S.,Tohoku University | Mishra O.P.,Geological Survey of India | Mishra O.P.,Disaster Management Center | And 2 more authors.
Tectonophysics | Year: 2011

To understand the genesis of the 25 March 2007 Noto-Hanto earthquake (Mw 6.6), we determined high-resolution 3-D seismic velocity (Vp and Vs) and Poisson's ratio (σ) images in the epicenter area using 24,698 P-wave and 22,927 S-wave arrival times from 809 earthquakes and 265 sP depth-phase data collected from seismograms of 162 earthquakes beneath the Japan Sea. The sub-oceanic events are relocated accurately by using P-, S- and sP depth-phase arrival time data jointly. Our results demonstrate that the seismic velocity (Vp and Vs) and Poisson's ratio (σ) vary markedly in the source area. In and around the main shock hypocenter, low-velocity and high-σ anomalies are revealed, which are apt for accumulation of differential strain to bring the brittle failure. We infer that the zone with pronounced low-velocity and high Poisson's ratio beneath the source area reflects fluid-related anomalies derived either from the dehydration of the subducting Pacific slab or from permeation of sea-water through deep-seated active faults or both to the main shock hypocenter, which in turn may have facilitated the rupture initiation of the main shock and its aftershock sequence by weakening the overlying seismogenic layer beneath the region. Our study reinforces the concept of fluid-driven earthquakes in the peninsular regions, elsewhere in the world. © 2011 Elsevier B.V.

Dutta P.K.,Jadavpur University | Naskar M.K.,Jadavpur University | Mishra O.P.,Disaster Management Center
Himalayan Geology | Year: 2012

In this study, we evaluate a geodynamical model based on the physical relationship between in-soil radon concentration and the effective stress pattern in the rock mass. Changes in subsurface radon concentration is dependent on pre-seismic stress and strain changes prior to earthquake occurrence. Mathematical models in seismo-geochemical monitoring are powerful tools for the study of quasi-elastic strain in which compression and extension strains decrease or increase the radon activity prior to an earthquake. Our study involves a radon gas volume analytic model to find the correlation of radon fluctuations to stress drop under compression and dilatation strain condition. In our paper, an analysis is performed of the coupling between deformation and pore fluid diffusion related to radon gas emanation prior to earthquake by evaluating their probability of occurrence through bayesian deterministic model. The study shows that it can be inferred using probabilistic framework involving exhalation of radon that earthquake occurs on recession of a curve of qualitative pattern of radon activity concentration change associated with stress change. Based on the inferences from the bayesian framework in connection with geodynamic processes, geochemical variations are linked to a more general seismogenic process and their connection with radon exhalation is established.

Dutta P.K.,Jadavpur University | Mishra O.P.,Disaster Management Center | Naskar M.K.,Jadavpur University
Central European Journal of Geosciences | Year: 2013

In the proposed study, non-linear behavioral patterns in the seismic regime for earthquakes in the Himalayan basin have been studied using a complete, verified EQ catalogue comprised of all major events and their aftershock sequences in the Himalayan basin for the past 110 years [1900-2010]. The dataset has been analyzed to give better decision making criteria for impending earthquakes. A series of statistical tests based on multi-dimensional rigorous statistical studies, inter-event distance analyses, and statistical time analyses have been used to obtain correlation dimensions. The time intervals of earthquakes within a seismic regime have been used to train the neural network to analyze the nature of earthquake patterns in the different clusters. The results obtained from descriptive statistics show high correlation with previously conducted gravity studies and radon anomaly variation. A study of the time of recurrence of the numerical properties of the regime for 60 years from 1950 to 2010 for the Himalayan belt for analysis of significant EQ failure events has been done to find the best fit for an empirical data probability distribution. The distribution of waiting time of swarm events occurring in the Himalayan basin follows a power-law model, while independent events do not fit the power-law distribution. This suggests that probability of the occurrence of swarm events [M ≤ 6.0] with frequent shaking may be more frequent than that of the occurrence of independent events of magnitude [M >6.0] in the Himalayan belt. We propose a three-layer feed forward neural network model to identify factors, with the actual occurrence of the maximum earthquake level M as input and target vectors in Himalayan basin area. We infer through a series of statistical results and evaluations that probabilistic forecasting of earthquakes can be achieved by finding the meta-stable cluster zones of the Himalayan clusters for the spatio-temporal distribution of earthquakes in the area. © 2013 Versita Warsaw and Springer-Verlag Wien.

Singh A.P.,Institute of Seismological Research ISR | Mishra O.P.,Geological Survey of India | Mishra O.P.,Disaster Management Center | Rastogi B.K.,Institute of Seismological Research ISR | Kumar D.,Kurukshetra University
Natural Hazards | Year: 2011

Several pieces of studies on the January 26, 2001, Bhuj earthquake (Mw 7.6) revealed that the mainshock was triggered on the hidden unmapped fault in the western part of Indian stable continental region that caused a huge loss in the entire Kachchh rift basin of Gujarat, India. Occurrences of infrequent earthquakes of Mw 7.6 due to existence of hidden and unmapped faults on the surface have become one of the key issues for geoscientific research, which need to be addressed for evolving plausible earthquake hazard mitigation model. In this study, we have carried out a detailed autopsy of the 2001 Bhuj earthquake source zone by applying three-dimensional (3-D) local earthquake tomography (LET) method to a completely new data set consisting of 576 local earthquakes recorded between November 2006 and April 2009 by a seismic network consisting of 22 numbers of three-component broadband digital seismograph stations. In the present study, a total of 7560 arrival times of P-wave (3820) and S-wave (3740) recorded at least 4 seismograph stations were inverted to assimilate 3-D P-wave velocity (Vp), S-wave velocity (Vs), and Poisson's ratio (σ) structures beneath the 2001 Bhuj earthquake source zone for reliable interpretation of the imaged anomalies and its bearing on earthquake hazard of the region. The source zone is located near the triple junction formed by juxtapositions of three Indian, Arabian, and Iranian tectonic plates that might have facilitated the process of brittle failure at a depth of 25 km beneath the KRB, Gujarat, which caused a gigantic loss to both property and persons of the region. There may be several hidden seismogenic faults around the epicentral zone of the 2001 Bhuj earthquake in the area, which are detectable using 3-D tomography to minimize earthquake hazard for a region. We infer that the use of detailed 3-D seismic tomography may offer potential information on hidden and unmapped faults beneath the plate interior to unravel the genesis of such big damaging earthquakes. This study may help in evolving a comprehensive earthquake risk mitigation model for regions of analogous geotectonic settings, elsewhere in the world. © 2011 Springer Science+Business Media B.V.

Singh A.P.,Institute of Seismological Research ISR | Mishra O.P.,Geological Survey of India | Mishra O.P.,Disaster Management Center | Yadav R.B.S.,Indian National Center for Ocean Information Services | Kumar D.,Kurukshetra University
Journal of Asian Earth Sciences | Year: 2012

The seismic characteristics of the 2001 Bhuj earthquake (Mw 7.6) has been examined from the proxy indicators, relative size distribution (3D b-value mapping) and seismic tomography using a new data set to understand the role of crustal heterogeneities in rupture initiations of the 2001 Bhuj earthquake of the Gujarat (India), one of the disastrous Indian earthquakes of the new millennium. The aftershocks sequence recorded by 22 seismograph stations of Gujarat Seismic Network (GSNet) during the period from 2006 to 2009, encompassing approximately 80 km × 70 km rupture area had revealed clustering of aftershocks at depth of 5-35 km, which is seismogenic layer responsible for the occurrence of continued aftershocks activity in the study region. The 3D b-value mapping estimated from a total of 3850 precisely located aftershocks with magnitude of completeness M c≥ 2.7 shows that a high b-value region is sandwiched within the main shock hypocenter at the depth of 20-25. km and low b-value region above and below of the 2001 Bhuj main shock hypocenter. Estimates of 3-D seismic velocity (Vp; Vs) and Poisson's ratio (b{cyrillic}) structure beneath the region demonstrated a very close correspondence with the b-value mapping that supports the similar physicochemical processes of retaining fluids within the fractured rock matrix beneath the 2001 Bhuj mainshock hypocenter. The overall b-value is estimated close to 1.0 which reveals that seismogenesis is related to crustal heterogeneity, which, in turn also supported by low-Vs and high-b{cyrillic} structures. The high b-value and high-b{cyrillic} anomaly at the depth of 20-25. km indicate the presence of highly fractured heterogeneous rock matrix with fluid intrusions into it at deeper depth beneath the main shock hypocenter region. Low b-value and high-Vp in the region is observed towards the north-east and north-west of the main shock that might be an indication of the existence of relatively competent rock masses with negligible volume of cracks that may have contained over-pressurized fluids without molten rocks. © 2012 Elsevier Ltd.

Singh A.P.,Institute of Seismological Research ISR | Mishra O.P.,Disaster Management Center | Kumar D.,Kurukshetra University | Kumar S.,Institute of Seismological Research ISR | Yadav R.B.S.,Indian National Center for Ocean Information Services
Journal of Earth System Science | Year: 2012

We analyzed 3365 relocated aftershocks with magnitude of completeness (Mc) ≥1.7 that occurred in the Kachchh Rift Basin (KRB) between August 2006 and December 2010. The analysis of the new aftershock catalogue has led to improved understanding of the subsurface structure and of the aftershock behaviour. We characterized aftershock behaviour in terms of a-value, b-value, spatial fractal dimension (D s), and slip ratio (ratio of the slip that occurred on the primary fault and that of the total slip). The estimated b-value is 1.05, which indicates that the earthquake occurred due to active tectonics in the region. The three dimensional b-value mapping shows that a high b-value region is sandwiched around the 2001 Bhuj mainshock hypocenter at depths of 20-25 km between two low b-value zones above and below this depth range. The D s-value was estimated from the double-logarithmic plot of the correlation integral and distance between hypocenters, and is found to be 2.64 ± 0.01, which indicates random spatial distribution beneath the source zone in a two-dimensional plane associated with fluid-filled fractures. A slip ratio of about 0.23 reveals that more slip occurred on secondary fault systems in and around the 2001 Bhuj earhquake (Mw 7.6) source zone in KRB. © Indian Academy of Sciences.

Lei J.,China Earthquake Administration | Xie F.,China Earthquake Administration | Mishra O.P.,Disaster Management Center | Lu Y.,China Earthquake Administration | And 2 more authors.
Bulletin of the Seismological Society of America | Year: 2012

A high-resolution tomographic model inferred from local and teleseismic arrival-time data under Yunnan, southwest China, shows that the 2011 Yingjiang earthquake (M 5.8) occurred around a low-velocity anomaly that extends down to the top of the mantle transition zone and is attributable to upwelling flow of the active Tengchong volcano. Fluids in the flow may mainly originate from the dehydration of the eastward subduction of the Indian plate in the mantle transition zone and have reached the fault zone. Our results suggest that the occurrence of the Yingjiang earthquake could be closely related to fluids that might enhance the stress concentration on the seismogenic layer, as well as decrease the effective normal stress across the fault planes of the Da Yingjiang fault. We conclude that the Yingjiang earthquake might be a volcano-related fluid-driven earthquake. The successive occurrence of small earthquakes (M > 4:0) and the Yingjiang aftershocks may imply recent magmatism at the Tengchong volcano. The 4 February 2011 Indo-Burma earthquake (M 6.4) occurred at ∼90 km depth, suggesting that the Indian plate is still active and currently subducting eastward, which may explain why several moderate-large earthquakes, such as the 24 March 2011 Burma earthquake (M 7.2), have occurred recently in the region.

Mishra O.P.,Disaster Management Center | Mishra O.P.,Geological Survey of India
Proceedings of the Indian National Science Academy | Year: 2012

The recent seismological research and studies in India are dominated by 1) studies on the spatio-temporal aspects of seismogenesis and seismotectonics of the Himalaya and its adjoining regions; 2) Seismological studies on tsunamigenic earthquake and earthquake pattern of the Andaman-Nicobar subduction region of India 3) studies on seismogenesis and seismotectonics of the Stable Continental region (SCR) of India; 4) studies on site response, seismic microzonation, earthquake risk, vulnerability, disaster management and risk mitigation strategies of India; 5) studies on earthquake precursor and prediction of earthquakes in India; 6) studies on seismological issues of outside India. The extensive seismological research in India is principally aimed at understanding the intricate seismological processes beneath the study region vis-a-vis elsewhere in the world having analogous seismotectonic and hydrological settings. Several pieces of outstanding multi-disciplinary detailed studies on the reservoir induced earthquakes have resulted in the formulation of a comprehensive project of "Deep Crustal Drilling" (DCD) in the Koyna-Warna region by involving several institutions of India to unravel the hidden mystery involved with reservoir induced earthquake nucleation and generating processes. A series of seismological publications on challenging issues by Indian researchers in different journals of global repute during the year 2007-2011 gives enough testimony of quality-based seismological research in India, which has significant bearing on opening up of new avenues for conducting leading edge advanced seismological research in the regional and global perspectives. © Printed in India.

Mishra O.P.,Disaster Management Center | Mishra O.P.,Geological Survey of India
Bulletin of the Seismological Society of America | Year: 2013

In order to resolve an enigmatic issue relating to the existence of fluidrelated or temperature-related anomalies at the mainshock hypocenter of the 2001 Bhuj, India, earthquake (Mw 7.6), an estimate of the 3D bulk-sound velocity structure is made from the inverted high-quality P- and S-arrival times from a total of 368 aftershocks recorded by 12 temporary seismic stations installed following the 2001 Bhuj earthquake. Results reveal strong lateral and vertical heterogeneity in bulk velocity (Vφ{symbol}) beneath the source zone. The 2001 Bhuj mainshock and its aftershock source zones are associated with anomalously high bulk-sound velocity (high Vφ{symbol}), indicating high bulk elastic strength of the source rocks at the mainshock hypocenter due to high pore pressures of the fully saturated cracked rocks associated with solute precipitation through the processes of acoustic fluidization and cementation. The interpretation of bulk velocity tomograms suggests that the processes of mineral dehydration and permeation of sea/surface water through several active Quaternary faults down to the deep crust might have contributed to in situ fluid-related material heterogeneity in bulk velocity within the fluid-filled fractured rock matrix in the paleorift zone at the 2001 Bhuj mainshock hypocenter, which in turn increased pore pressure, lowered the effective stress, and brought the system into a brittle failure. High Vφ in the intersecting fault geometry in the fractured rock matrix at the mainshock hypocenter can be taken as evidence for the strong role of fluids in association with the intraplate earthquake of the Indian peninsula. © 2013 by the Seismological Society of America.

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