Earthquake forerunner as probable precursor — an example from north burma subduction zone     

Sujit Dasgupta  Basab Mukhopadhyay  Manoj Mukhopadhyay 《Journal of the Geological Society of India》2012,80(3):393-402

The Burmese Arc seismic activity is not uniform for its ∼ 1100 km length; only the Northern Burmese Arc (NBA) is intensely active. Six large earthquakes in the magnitude range 6.1–7.4 have originated from the NBA Benioff zone between 1954–2011, within an area of 200 × 300 km² where the Indian plate subducts eastward to depths beyond 200 km below the Burma plate. An analysis on seismogenesis of this interplate region suggests that while the subducting lithosphere is characterized by profuse seismicity, seismicity in the overriding plate is rather few. Large earthquakes occurring in the overriding plate are associated with the backarc Shan-Sagaing Fault (SSF) further east. The forecasting performance of the Benioff zone earthquakes in NBA as forerunner is analysed here by: (i) spatial earthquake clustering, (ii) seismic cycles and their temporal quiescence and (iii) the characteristic temporal b-value changes. Three such clusters (C1–C3) are identified from NBA Benioff Zones I & II that are capable of generating earthquakes in the magnitude ranges of 7.38 to 7.93. Seismic cycles evidenced for the Zone I displayed distinct quiescence (Q₁, Q₂ and Q₃) prior to the 6^th August 1988 (M 6.6) earthquake. Similar cycles were used to forecast an earthquake (Dasgupta et al. 2010) to come from the Zone I (cluster C1); which, actually struck on 4 February 2011 (M 6.3). The preparatory activity for an event has already been set in the Zone II and we speculate its occurrence as a large event (M > 6.0) possibly within the year 2012, somewhere close to cluster C3. Temporal analysis of b-value indicates a rise before an ensuing large earthquake.  相似文献   

A preliminary investigation of the hydrocarbon content of groundwater of Kuwait     

E. Al-Awadi  A. Mukhopadhyay  M. Quinn  T. Saeed  A. Hauser 《Environmental Geology》2001,41(3-4):330-340

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The geometry of the Burmese-Andaman subducting lithosphere     

Sujit Dasgupta  Manoj Mukhopadhyay  Auditeya Bhattacharya  Tapan K. Jana 《Journal of Seismology》2003,7(2):155-174

The gross seismotectonic features for the Burmese-Andaman arc system which defines the northeast margin of the Indian plate are rather well known but variations in the subduction zone geometry along and across the arc and fault pattern within the subducting Indian plate have not been studied. Present workaims to study these by using seismicity data whose results are presented in the form of: (a) Lithospheric across-the-arc sections at about every 100–120 km (approximately one degree latitude apart) covering the 3500 km longBurmese-Andaman arc system, (b) a structure contour map showing the depth tothe top surface of the seismically active lithosphere and (c) interpretationof focal mechanism solutions for 148 Benioff zone earthquakes. Both penetrationdepth and the dip of the Benioff zone vary considerably along the arc in correspondence to the curvature of the fold-thrust belt which varies from concave to convex in different sectors of the arc. Several extensive `Hinge faults' that abut at high angles to the arc orientation, are inferred from aninterpretation of the structure contour map. Active nature of the hinge faultsis established in several areas by their association with earthquakes andcorroborated through fault plane solutions. At shallow level of the Benioffzone along these faults, focal mechanism solutions display left lateral strikeslip movement while at deeper levels reverse fault solutions are common.  相似文献   

Mineralogical speciation of elements in an eastern Canadian feed coal and their combustion residues from a Canadian power plant     

P. K. Mukhopadhyay  G. Lajeunesse  A. L. Crandlemire 《International Journal of Coal Geology》1996,32(1-4)

Systematic changes in mineralogy, enrichment and depletion of selected elements, and mineralogical speciation of selected elements in fly ash and bottom ash samples from the Lingan Power Plant were compared to run-of-mine and pulverized feed coal from the Sydney coalfield, Nova Scotia, eastern Canada. The analytical techniques used were an electron microprobe equipped with energy and wavelength X-ray dispersive spectrometers, X-ray diffraction, neutron activation, scanning electron microscopy with energy dispersive X-ray and incident light petrography. Three types of glasses (Fe/O-rich, Fe/Al/Si/O-rich and or Al/Si/O-rich) were identified in the combustion residues; they were formed as a result of the interaction of melted pyrite and clay minerals. Compared to the feed coal, most elements were enriched 10 to20 times in the fly ash. The concentration of the elements in both the fly ash and bottom ash are comparable to coal ash that is generated by the low temperature asher in the laboratory. Some chalcophile elements such as arsenic and lead occurred as a solid solution in pyrite in the feed coal and were concentrated in the float fraction (density: <2.81 g/cm³) of the fly ash with non-crystalline Fe-oxides. X-ray mapping of arsenic in the fly ash and bottom ash indicates that arsenic was evenly distributed as oxide within the Fe/O- and Fe/Al/Si/O-rich glass and crystalline phases in the fly ash, possibly in solid solution. Arsenic is associated with Fe/O and Fe/S crystalline phases in the bottom ash.  相似文献   

Morphological variations in the polymetallic nodules from selected stations in the central Indian Ocean     

Ranadhir Mukhopadhyay 《Geo-Marine Letters》1987,7(1):45-51

Polymetallic nodules from the Central Indian Ocean largely range in size from 2 to 6 cm. The smaller nodules (<4 cm) are subspheroidal to spheroidal in shape and with the increase in size, nodules become more discoidal and elongated. The size and relief of mammillae vary with the size of nodules. Polynucleate nodules are more abundant in larger size classes (>6 cm) and in stations closer to the oceanic ridge. Density varies significantly with shape; less rounded nodules are denser than well-rounded ones.  相似文献   

Fine-scale analysis of shelf–slope physiography across the western continental margin of India     

B. Chakraborty  R. Mukhopadhyay  P. Jauhari  V. Mahale  K. Shashikumar  M. Rajesh 《Geo-Marine Letters》2006,26(2):114-119

We attempt here to quantify and model physiographic features off the central west coast of India in terms of power spectral exponent, amplitude parameter. We demonstrate that statistical analysis of multi-beam echo-sounder grid bathymetry data is able to characterise the outer shelf, upper slope, shelf margin basin and several structural rises in the region. A scatter diagram analysis shows that the seafloor data can be grouped into two distinct clusters. Distinctly different clustering patterns are observed over the structural rises, compared to the shelf, slope and basinal areas. This suggests different modes of formation for the members of these two clusters. In fact, the steep structural rises appear to be part of the NW–SE-trending coast-parallel Mid-Shelf Basement and Prathap ridges. These ridges are rift-induced volcanic emplacements on a stretched and thinned continental crust which probably formed during mid-Cretaceous times.  相似文献   

Disappearance of the New Moore Island from the Southernmost Coastal Fringe of the Sundarban Delta - A Case Study     

Sugata Hazra  Anirban Mukhopadhyay  Samadrita Mukherjee  Anirban Akhand  Abhra Chanda  Debasish Mitra  Tuhin Ghosh 《Journal of the Indian Society of Remote Sensing》2016,44(3):479-484

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Morphotectonic and petrological variations along the southern Central Indian Ridge     

Ranadhir Mukhopadhyay  Sridhar D. Iyer  Dwijesh Ray  S. M. Karisiddaiah  Rajendra K. Drolia 《International Journal of Earth Sciences》2016,105(3):905-920

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Distribution of Transmissivity in the Dammam Limestone Formation, Kuwait   总被引：1，自引：0，他引：1  

Amitabha Mukhopadhyay 《Ground water》1995,33(5):801-805

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An analysis of the gravity field over north Singhbhum, Bihar, India     

R.K. Verma  Manoj Mukhopadhyay  S.K. Roy  R.P.P. Sinha 《Tectonophysics》1978,44(1-4)

About seven hundred gravity stations were established 2–3 miles apart over the Precambrian terrain of Singhbhum that lies between latitude 22° 15′ to 23°°15′N and longitude 85° to 87°E. Bouguer anomalies ranging from +4 to −62 mGal are found in the area. The observed Bouguer anomaly map was analyzed into regional and residual components. The residual anomaly map shows an excellent correlation with geology. The Singhbhum granite batholith is associated with several gravity lows. The residual anomaly map outlines nine plutonic granitic masses within the Singhbhum batholith. Negative residuals are also observed over some intrusive granites outside the batholith. Residual gravity highs are noted over the Dalma hill as well as over the Dhanjori lava complex on the eastern part of the Singhbhum batholith.Two-dimensional models suggestive of subsurface configuration of several major geologic units in the area are presented. These indicate that some of the plutonic granites within the Singhbhum batholith are of relatively large dimensions. The basin containing the Iron Ore Group of rocks to the west of the batholith, as well as the basin containing Singhbhum Group of rocks outside the Copper Belt thrust, may have sedimentary thicknesses of the order of 6–7 km. The Dalma lavas attain their maximum thickness of about 2.5 km in the form of a syncline, underneath which the Singhbhum Group of rocks is also found to be the thickest. The Copper Belt thrust, a major Precambrian fracture around the Singhbhum batholith, is moderately north-dipping near the surface but possibly attains a steeper slope at depth. The thrust appears to be quite deep seated. A threedimensional computer-based model for the Dhanjori lava—gabbro complex on the eastern part of the Singhbhum batholith has been deduced. Maximum thickness of these basic rocks is found to exist underneath a thin cap of granophyre. The geological implication of these results is discussed.Variation in the regional anomalies seems to be attributable to a mass deficiency under the Singhbhum batholith. The batholith may extend subsurfacially towards the north across the Copper Belt thrust. The northern tip of the batholith probably became dissected along the line of intersection of the two orogenic trends in the area and subsided. Over this subsided part, the Singhbhum Group of rocks was deposited at a later stage. Gravity data suggest a fairly large amount of subsidence in the area.  相似文献