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Papers by R. Dattatrayam

Bulletin of the Seismological Society of America, 2004

We study the source time function (STF) and radiated seismic energy (E R) of the M w 7.6 Bhuj ear... more We study the source time function (STF) and radiated seismic energy (E R) of the M w 7.6 Bhuj earthquake using the empirical Green's function (EGF) technique. Our estimations of the STF and E R are based on teleseismic P waves and regional seismograms, respectively. We find that the STFs as a function of azimuth have a similar shape and nearly constant duration of 18 sec. This suggests that the rupture propagation was essentially radial. The STFs show a sharp rise in the first 6 sec. The E R estimated from the EGF technique is 2.1 ‫ן‬ 10 23 erg. We find that E R 's computed from integration of corrected velocity-squared spectra of teleseismic P waves and regional seismograms are in excellent agreement with the E R obtained from the EGF technique. Since the seismic moment, M 0 , is 3.4 ‫ן‬ 10 27 dyne cm, we obtain E R /M 0 ‫ס‬ 6.2 ‫ן‬ 10 ‫5מ‬. The radiation efficiency, g R , during the Bhuj earthquake was low, about 0.23. The sharp rise of the STFs and g R ‫ס‬ 0.23 can be explained by Sato and Hirasawa's (1973) quasi-dynamic, circular source model with an effective stress of ϳ300 bar and the ratio of rupture to shear-wave velocity, V R /b, of ϳ0.5. The corresponding estimate of slip velocity at the center of the fault is 156 cm/sec. V R /b ϳ 0.5 is in reasonable agreement with the duration of the STF and the reported dimension of the aftershocks, as well as with the results of inversion of teleseismic body waves. The observations may also be explained by a frictional sliding model, with gradual frictional stress drop and significant dissipation of energy on the fault plane. This model requires an average dynamic stress drop of about 120 bar and V R /b ϳ 0.7 to explain both the rapid rise in the first 6 sec of the STFs and, along with a static stress drop of 200 bar, the observed E R /M 0. High static stress drop is a common feature of most crustal earthquakes in stable continental regions. An examination of the available data, however, does not suggest that most of them also have relatively low radiation efficiency.

MAUSAM, 2021

Slip vectors of thirty-nine thrust events occurring along the Himalayan collision zone have been ... more Slip vectors of thirty-nine thrust events occurring along the Himalayan collision zone have been compared with the velocity vectors between the Indian-Eurasian plates derived from the RM 2 and NUVEL 1 models, The observed deviations of the slip vector from the velocity vector have been interpreted in terms of a simple kinematic model according to which the eastern and western blocks of south Tibet are separating from each other, From the model it is estimated that the western and eastern blocks of Tibet are moving at the rate of 3.6 cm/year westwards at 76°Eand 2.6 cm/year eastwards at 94°E with respect to Eurasia respectively, resulting in an east-west extension, projected to the trend at 85°E, at the rate of 5, 5 cm/year. This would correspond to a strain rate of about 6.9 x 10-8year in central Tibetan region.

MAUSAM, 2021

Fault plane solutions and focal depths for three crustal events occurring in the Himalayan collis... more Fault plane solutions and focal depths for three crustal events occurring in the Himalayan collision zone have been obtained using synthetic waveform modelling. Two crustal events with their epicenters in the Tibetan plateau show large component of normal faulting with east-west trading T-axes. The third event with It’s epicenter north of Main Boundary Thrust (MBT) shows reverse faulting with the nodal planes paralleling the local structural trend. All the three crustal events studied have occurred at shallow focal depths of less than 15 km. The Inferred source parameters of these events are discussed In the light of active tectonics of the region.

Bulletin of the Seismological Society of America, 2004

MAUSAM

Empirical formulae have been developed to estimate the magnitude of earthquakes from, 'coda d... more Empirical formulae have been developed to estimate the magnitude of earthquakes from, 'coda duration', The coda durations read from the seismograms of WYSSN/SRO/Helicorder systems of Shillong, New Delhi and Bombay observatories have been calibrated with reference to the local Richter’s magnitude, Three models have been tested with the data using regression analysis., The fitness of the models with the data is ( valuated in terms of correlation coefficient and standard error of estimate; The effects of epicentral, distance, coda duration and duration magnitude' on magnitude residuals is also examined and discussed is found that magnitude residuals do not show any systematic variation with these parameters.

MAUSAM, 2022

The Uttarkashi earthquake of 20 October 1991, which caused widespread damage in the Galhwal Himal... more The Uttarkashi earthquake of 20 October 1991, which caused widespread damage in the Galhwal Himalayan region, was followed by a prominent aftershock. activity extending over a period of about two months. The aftershock activity was monitored using temporary networks established after the mainshock and the permanent stations in operation in the region. About 142 aftershocks could be located accurately using the data of these stations. The b-value of the Gutenberg-Richter's relationship for the aftershock sequence works out to be 0.6. The temporal distribution of the aftershocks suggests a hyperbolic decay with a decay constant (p) of 1.17. Macroseismic observations derived from field surveys show good agreement with the instrumentally determined source parameters.

MAUSAM, 2021

The collision of Indian and Eurasian continents caused large scale deformation and high seismicit... more The collision of Indian and Eurasian continents caused large scale deformation and high seismicityof vast areas of both continents in the geological history. The North-West portion of the Himalayan arc which is lyingunder the rupture zones of Kangra earthquake of 1905, Uttarkashi earthquake of 1991 and Chamoli earthquake in 1999,has experienced many earthquakes of magnitude 6 and above. The region of North-West India between 30.0º - 35.0ºNorth and 73.0º - 79.0º East is, therefore, under intense investigations by various scientists since the origin of theHimalayas. India Meteorological Department had opened thirteen seismic observatories in early sixties for monitoringof earthquake activities in and around Bhakra, Pong, Pandoh dams in Punjab / Himachal Pradesh and Salal dam inJ&K on specific demand of the dam authorities. These observatories have recorded the earthquakes occurred in thisregion having magnitude even less than 2. The data collected for the last two decades is very usef...

Current Science, 2002

An earthquake of magnitude (M L ) 5.0 occurred on 12 December 2000 in the bordering regions of Id... more An earthquake of magnitude (M L ) 5.0 occurred on 12 December 2000 in the bordering regions of Idukki and Kottayam districts of Kerala followed by a series of aftershocks. After a brief lull, another earthquake of magnitude (M L ) 4.8 occurred in the same region on 7 January 2001, which was also followed by a series of aftershocks for a short spell. These events were monitored by permanent seismological observatories in the region as well as by operating temporary field observatories. The waveforms of broadband digital seismographs at two stations located approximately 98 and 128 km from the epicentre show that both the main events indicate similar focal mechanisms. P-wave first motion data and waveform inversion yield a focal mechanism solution with one nodal plane trending along NW direction and the other along ENE direction with predominant strike-slip component. The epicentral distribution indicates a cluster in a N-S direction passing through Erratupetta (Kottayam District). Th...

CURRENT SCIENCE, VOL. 86, NO. 8, 25 APRIL 2004 1161 *For correspondence. (e-mail: afzal1235@redif... more CURRENT SCIENCE, VOL. 86, NO. 8, 25 APRIL 2004 1161 *For correspondence. (e-mail: afzal1235@rediffmail.com) 4. Randles, J. W. and Rathjen, J. P., In Virus Taxonomy. Sixth Report of the International Committee on Taxonomy of Viruses (eds Murphy, F. A. et al.), Springer-Verlag, Vienna, 1995, pp. 379– 383. 5. Bosque-Perez, N. A. and Buddenhagen, I. W., Plant Dis., 1990, 74, 372–378. 6. Carazo, G., de Blas, C., Saiz, M., Romero, J. and Castro, S., Plant Dis., 1993, 77, 210. 7. Reddy, M. V., Nene, Y. L. and Verma, J. P., Int. Chickpea Newsl., 1979, 1, 8. 8. Horn, N. M., Reddy, S. V., Roberts, I. M. and Reddy, D. V. R., Ann. Appl. Biol., 1993, 122, 467–479. 9. Horn, N. M., Reddy, S. V., van den Heuvel, J. F. J. M. and Reddy, D. V. R., Plant Dis., 1996, 80, 286–290. 10. Naidu, R. A., Mayo, M. A., Reddy, S. V., Jolly, C. A. and Torrence, L., Ann. Appl. Biol., 1997, 130, 37–47. 11. D’Arcy, C. J., Domier, L. L. and Mayo, M. A., In Virus Taxonomy. Seventh Report of the International Committee ...

ol, S6/4 'I'i~I ABST RACf. Re ecurrence intervals for earthquake" of magnitudes from 5 .0 to 8. 5... more ol, S6/4 'I'i~I ABST RACf. Re ecurrence intervals for earthquake" of magnitudes from 5 .0 to 8. 5 have been worked OUI using Gumbel' s extreme value theory and compared with those de termined by Gutenberg-Richter's frequencymagnitude relationship for six regio ns, name ly. (A) Hind ukush. (B) Kashmir and Himachal Pradesh. (C) Indiawe... tern Nepal border, «(») Ncpal-Sikkirn border, (E) No rtheast India and (F) Andaman and Nicobar Islands. A data sam ple fo r the period 1962 to 1976 and anether for a longer period have been used for the purpose and limitations of the results obtained arc discu ssed. Gumbel's ex treme value theory gives better estimates of the: return period of the maximum magnitude earthq uakes when da ta for longer period i" taken. The rC'CUr~DC'C intervals thu s estimated for earthquake" of magnitud e Rjfi (or the si'(region" arc 22/2. 203/1 0, 222/11, 160/9, 34/4 and 5R/4 years respectively.

Journal of Earth System Science, 2003

Site response in and around Delhi is studied using digital seismograms recorded by a thirteenstat... more Site response in and around Delhi is studied using digital seismograms recorded by a thirteenstation VSAT-based 24-bit digital Delhi telemetry network of the India Meteorological Department. Nine local (M l ≥ 2.3) and nine regional (M l ≥ 3.9) earthquakes are selected for the estimation of site amplification factor using the classical standard spectral ratio for regional events (Ridge Delhi Observatory being the reference station), normalized standard spectral ratio for local events, horizontal-to-vertical spectral ratio or receiver function and the generalized inversion techniques in the frequency range of 0.5 to 7.5 Hz. Site response curves at all the thirteen stations exhibit station to station variation of the site amplification factor reflecting the changes in geologic/geotectonic/soil conditions. A comparison of the site response values obtained by the generalized inversion with those computed using receiver function technique shows a large scatter even though the pattern of the curves remain more or less similar. However, the site effects computed by generalized inversion and standard spectral ratio exhibit a good 1:1 correspondence. The peaks yielded by all the methods have been observed to occur at the same frequencies. It is evident that the softer fluvial deposits of the newer alluvium of the east Yamuna sector show steeper site amplification gradient at lower frequencies, while the greater Delhi experiences moderate site amplification. The variation of site response corroborates the abrupt changes in intensity from one location to another due to local site condition.

$Research paper thumbnail of Temporal clustering of earthquakes: a fractal approach$

Current science, 1994

... Titre du document / Document title. Temporal clustering of earthquakes : a fractal approach. ... more ... Titre du document / Document title. Temporal clustering of earthquakes : a fractal approach. Auteur(s) / Author(s). DATTATRAYAM RS (1) ; KAMBLE VP ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). (1) Dep. sci. ... Asie. ; Mots-clés espagnols / Spanish Keywords. Sismo. ; ...

We present a preliminary source study of the Muzaffarabad earthquake of 8 October 2005 (Mw 7.6) a... more We present a preliminary source study of the Muzaffarabad earthquake of 8 October 2005 (Mw 7.6) and the far-field ground motions that it generated. Our analysis is based on regional broadband seismograms recorded at stations operated by the India Meteorological Department (IMD) which are situated to the south of the epicentre, and at non-IMD stations which are located to the north. We find that the source spectrum of the earthquake is reasonably consistent with ω 2 -source model with a seismic moment, M 0 , of 2.94 x 10 20 N-m and a corner frequency, fc, of 0.051 Hz (Brune stress drop of 9.5 MPa). The radiated seismic energy, E R , estimated from the empirical Green's function (EGF) technique is 2.70 × 10 16 J. This yields a normalized radiated energy, E R /M 0 , of 9.1 × 10 -5 , and an apparent stress, τ a , of 2.7 MPa. The rupture area of 100 × 15 km2 (estimated from slip distribution mapped from the inversion of teleseismic body waves) gives a static stress drop of about 11.3 MPa. From these source parameters we estimate a radiation efficiency of 0.49, implying a 'brittle' rupture typical of interplate events. Stochastic method requires a stress drop of -10 MPa to explain the observed peak ground motions (A max and V max ) recorded at regional distances, and predicts A max and V max exceeding 1 g and 100 cm/s, respectively at hard sites in the epicentral region. The source parameters and far-field ground motions of the Muzaffarabad and Bhuj earthquakes are quite similar even though the tectonic environment and the depth of their occurrence are distinct.

GeoScienceWorld, Dec 1, 1999

... Several authors have reported Q of Lg waves in the ENA: Q(f) = 900f °2 (Hasegawa, 1985); Q(f)... more ... Several authors have reported Q of Lg waves in the ENA: Q(f) = 900f °2 (Hasegawa, 1985); Q(f) = 500f °&amp;amp;#x27;65 (Shin and Herrmann, 1987); Q(f) = 800f °&amp;amp;#x27;3z (Gupta and McLaughlin, 1987); and Q(f) = ll 0 0 f °&amp;amp;#x27;19 (Chun et al., 1987). ...

In the past few decades" historical recordings of a scientific nature has taken up a critica... more In the past few decades" historical recordings of a scientific nature has taken up a critical importance in the different sectors of seismology: historical seismology and historical seismometry. Modern technologies now offer unique opportunities to catalog and efficiently distribute the reproductions into digital versions of scientific records. In order to mitigate earthquake hazards, it is important to study and learn from the past earthquakes. Seismograms contain the basic observational data for earthquake studies and must be archived properly and made available to the seismologists for further research. Seismologists normally prefer to work with digital seismograms that can be processed and analyzed easily and quickly. Old seismograms contain a lot of information useful for the study of historical earthquakes as correctly stated Ferrari, (1997). It is necessary to extract this information by digitizing the analog seismograms by using modern analysis tools. There are a few ap...

Journal of the Geological Society of India, 2012

14. Maron, D. M. and Ames, B. N., Revised methods for the salmonella mutagenicity test. Mutat. Re... more 14. Maron, D. M. and Ames, B. N., Revised methods for the salmonella mutagenicity test. Mutat. Res., 1983, 113, 173-215. 15. Perry, P. and Wolff, S., New Giemsa method for differential staining of sister chromatids. Nature. 1974, 251, 156-158. 16. Schneider, E. L., Nakanishi, Y., Lewis, J. and Sternberg, H., Simultaneous examination of sister chromatid exchanges and cell replication kinetics in tumour and normal cells in vivo. Cancer An o-quinone form of estrogen produces free radicals in human breast cancer cells: correlation with DNA damage. Chem. Res. Toxicol., 1994, 7, 23-28. 20. Martelli, A., Mattioli, F., Angiola, M., Reimann, R. and Brambilla, G., Species, sex and inter-individual differences in DNA repair induced by nine sex steroids in primary cultures of rats and human hepatocytes. Mutat. Res., 2003, 536, 69-78. 21. Werner, S., Kunz, S., Beckurts, T., Heidecke, C. D., Wolff, T. and Schwarz, L. R., Formation of DNA adduct by cyproterone acetate and some structural analogues in primary cultures of human hepatocytes. Mutat. Res., 1997, 395, 179-187. 22. Islam, S., Shafiullah and Ahmad, M., Mutagenic activity of certain synthetic steroids: Structural requirement for mutagenic activity in Salmonella and E. coli. Mutagen, 1991, 259, 177-187. 23. Tucker, J. D. and Preston, R. J., Chromosome aberrations, micronuclei, aneuploidy, sister chromatid exchanges and cancer risk assessment. Mutat. Res., 1996, 365, 147-159. 24. Painter, R. B., A replication model for sister chromatid exchange. Recommended protocols based on a survey of current practice in genotoxicity testing laboratories, IV. Chromosome aberration and sister chromatid exchange in Chinese hamster ovary V79, Chinese hamster lung and human lymphocytes cultures. Mutat. Res., 1991, 246, 301-322. 27. Gebhart, E., Sister chromatid exchange (SCE) and structural chromosome aberrations in mutagenicity testing. Hum. Genet., 1981, 58, 235-254. An ancient harbour at Dwarka: Study based on the recent underwater explorations A. S. Gaur, Sundaresh and Sila Tripati Ancient anchors off Tamil Nadu coast and ship tonnage analysis N. Athiyaman and P. Jayakumar

Current science

Though the Delhi earthquake of 27 August 1960 is important in understanding seismic hazard to the... more Though the Delhi earthquake of 27 August 1960 is important in understanding seismic hazard to the city, there is an uncertainty associated with its reported epicentre, depth and magnitude. The reported epicentres given in different catalogues are not consistent with felt and damage reports, and the depths (58–109 km) are also inconsistent with recorded waveforms (including the excitation of Lg waves), decay of seismic intensities with distance, number of aftershocks, earthquake sound and seismotectonics of the region. The reported magnitude of the earthquake varies between 5.3 and 6.0. We have performed an exhaustive analysis of the available information, including comparison of the seismograms of the 1960 earthquake with six recent well-recorded events as well as with the Moradabad earthquake of 1966. We find that: (1) A more reliable epicentre as compared to the instrumentally determined one, is provided by the locus of the strongest seismic intensity: 28.47°N, 77.00°E (between De...

Proceedings of the Indian National Science Academy, 2014

The process of dealing with earthquake disasters essentially involves three most important and in... more The process of dealing with earthquake disasters essentially involves three most important and inter-dependent components -(i) comprehensive understanding of the earthquake generation processes and the interior of the earth, (ii) disaster mitigation and preventive measures, and (iii) work through the ultimate goal of earthquake prediction. The basic and primary requirement towards addressing all these tasks is -high quality seismological data which is homogeneous and complete in time and space. India Meteorological Department (IMD), under the Earth System Science Organization (ESSO), Ministry of Earth Sciences (MoES), is the nodal agency of Government of India for monitoring earthquake activity in and around the country. IMD maintains the national seismological network consisting of a total of 82 observatories spread over the length and breadth of the country. The paper aims at discussing different methods/approaches adopted by IMD and other major agencies in the country for generation of various types of earthquake data products in standard formats, the analyses and archival tools and policy guidelines for supply and sharing amongst the user agencies. The paper also deals with the types of seismic instrumentation/networks in operation, network growth through historical times, data completion aspects, present level(s) of earthquake detection and location, future requirements and plans of upgradation. The policy guidelines being followed for seismological data sharing and supply have also been highlighted.

Bulletin of the Seismological Society of America, 2004

MAUSAM, 2021

Bulletin of the Seismological Society of America, 2004

MAUSAM

MAUSAM, 2022

MAUSAM, 2021

Current Science, 2002

Journal of Earth System Science, 2003

$Research paper thumbnail of Temporal clustering of earthquakes: a fractal approach$

Current science, 1994

GeoScienceWorld, Dec 1, 1999

Journal of the Geological Society of India, 2012

Current science

Proceedings of the Indian National Science Academy, 2014