Three‐dimensional model of the Koyna area of Maharashtra State (India) based on the spectral analysis of aeromagnetic data

Negi, Janardan G.; Agrawal, Parul; Rao, K. Nageswara

doi:10.1190/1.1441522

Cited by 39 publications

(24 citation statements)

References 9 publications

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“…These results clearly show that the epicentral zone is characterised by higher velocities in the crustal part. It is interesting to examine the aeromagnetic data acquired in the Koyna region over 13 short profiles each of 100 km in length at spacing of 4 km [Negi et al, 1983]. The seismic zone is also mapped as magnetic lineament from aeromagnetic studies [Talwani, 1997] In KSZ the seismicity is associated with the high velocity anomaly and this feature could be associated with more brittle and competent rock with ability to store strain energy and release it as brittle failure.…”

Section: Discussionmentioning

confidence: 99%

Evidence for high velocity in Koyna seismic zone from P‐wave teleseismic imaging

Srinagesh¹,

Singh²,

Reddy³

et al. 2000

Geophysical Research Letters

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Abstract. Three-dimensional P-wave velocity structure of the crust and upper most mantle beneath the Koyna Seismic Zone (KSZ) was determined by inverting 780 P-wave teleseismic travel times recorded by a 20 station digital network. The velocity image obtained through damped least square was tested for its resolution using checkerboard approach. The results of the inversion show strong lateral velocity variations of 6% to 7% within the study region. A high velocity anomaly (2% to 5%) in the upper and lower crust beneath the KSZ is flanked by lower velocity (-2% to -5%) anomalies on either side. The correlation of high-velocity with the seismic zone suggests that the earthquakes are occurring in more rigid rocks with increasing ability to store strain energy and release it as brittle failure.

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Section: Discussionmentioning

confidence: 99%

Evidence for high velocity in Koyna seismic zone from P‐wave teleseismic imaging

Srinagesh¹,

Singh²,

Reddy³

et al. 2000

Geophysical Research Letters

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“…The lateral extent of this fault is between the Koyna Dam and the right angle turn to the east in the Koyna River. Both the aeromagnetic data (NEGI et al, 1983) and seismic refraction data (KAILA et al, 1981) show that on a E-W profile through Koyna, the basalt is thicker under Koyna than under Alore to its west. The aeromagnetic data also show that there is a N -S to N10°E-S10°W trending fault along the Koyna River that extends at least 40 km to the south.…”

Section: B Koyna-ri6er Fault Zonementioning

confidence: 99%

“…In an effort to determine the thickness of the Deccan Trap rocks in the Koyna area, aeromagnetic data were acquired on 13 short profiles, each about 100 km long and spaced at 4 km (NEGI et al, 1983). Data were recorded at elevations of 1220, 1524 and 2134 m, above mean sea level.…”

Section: D3 Aeromagnetic Datamentioning

confidence: 99%

Seismotectonics of the Koyna-Warna Area, India

Talwani

1997

Pure appl. geophys.

112

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Reservoir-induced seismicity has been observed near Koyna Dam, India since the early 1960s. In order to understand the seismotectonics of the region we analyzed available seismicity data from 1963 to 1995. Over 300 earthquakes with M] 3.0 were relocated using revised location parameters (station locations, velocity model, station delays and V p /V s ratio). The spatial pattern of earthquakes was integrated with available geological, geophysical, geomorphological data and observations following the M 6.3 earthquake in December 1967, to delineate and identify the geometry of seismogenic structures. From this integration we conclude that the area lying between Koyna and Warna Rivers can be divided into several seismogenic crustal blocks, underlain by a fluid-filled fracture zone. This zone lies between 6 and 13 km and is the location of the larger events (M ]3.0). The seismicity is bounded to the west by the Koyna River fault zone (KRFZ) which dips steeply to the west. KRFZ lies along the N -S portion of the Koyna River and extends S10°W for at least 40 km. It was the location of the 1967 Koyna earthquake. The seismicity is bounded to the east by NE -SW trending Patan fault, which extends from Patan on the Koyna River, SW to near Ambole on the Warna River. Patan fault dips 45°to the NW and was the location of the M 5.4 earthquake in February 1994. The bounding KRFZ and Patan fault are intersected by several NW -SE fractures which extend from near surface to hypocentral depths. They form steep boundaries of the crustal blocks and provide conduits for fluid pressure flow to hypocentral depths. Sharp bends in the Koyna and Warna rivers (6 km south of Koyna Dam and near Sonarli, respectively) are locations of stress build-up and the observed seismicity.

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“…The utility of the Fourier spectral technique has been well established in estimating the average depth to various subsurface discontinuities from the potential field data (Spector and Grant 1970;Hahn et al 1976;Negi et al 1983Negi et al , 1986aNegi and Agrawal 1986). This technique treats the observed potential field anomalies, originating from line sources at various subsurface levels, as a statistical population.…”

Section: Spectral Analysismentioning

confidence: 99%

Lithospheric structure beneath Laxmi Ridge and late Cretaceous geodynamic events

1995

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Abstraet The geophysically unusual Laxmi Ridge (eastern basin, Arabian Sea) is associated with a prominent elongated negative gravity anomaly. A seismically and geodynamically constrained detailed 2D gravity modeling suggests an ll-km-thick normal oceanic crust and an asthenospheric upwarp to a depth of 35 km. We attribute the apparent thickening of the crust to a possible emplacement of an anomalous subcrustal low-density layer between 11 and 19 km depth. We hypothesize that a K-T boundary bolide impact near the Bombay offshore led to several geological events, including eruption of Deccan flood basalts. The spreading Carlsberg Ridge in the Indian Ocean and rifting associated with Deccan volcanism generated the compressive regime, which perhaps originated the Laxmi Ridge.

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Three‐dimensional model of the Koyna area of Maharashtra State (India) based on the spectral analysis of aeromagnetic data

Cited by 39 publications

References 9 publications

Evidence for high velocity in Koyna seismic zone from P‐wave teleseismic imaging

Evidence for high velocity in Koyna seismic zone from P‐wave teleseismic imaging

Seismotectonics of the Koyna-Warna Area, India

Lithospheric structure beneath Laxmi Ridge and late Cretaceous geodynamic events

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