Abstract
The slow spreading mid-Indian Ocean ridge system containing the Carlsberg, Central and Southwest Indian ridges is seismically very active. In the present study, a detailed analysis has been carried out of the data of earthquake sources along different ridge segments in order to investigate the spatial and temporal clustering patterns and to evaluate crustal processes related to the swarm occurrences along these ridges. The spatial and temporal clustering pattern of the recent earthquakes (1980–1990) pertaining to nine major spreading segments and eight fracture zones suggests that the events cluster in greater proportion along the spreading segments than along the fracture zones.
We performed a systematic search of earthquake catalogue during the period 1964–1990 by examining the spatio-temporal hypocentral clusters in order to identify the swarm occurrences along these ridges. The search included eighteen prominent sequences, of which, thirteen were earthquake swarms. Except two, all other swarms were found to be occurring mainly on the spreading segments. The maximum magnitude observed in these swarms is mb = 5.4 and have many events predominantly showing normal faulting mechanisms. The spatial disposition and temporal activity of the events in swarms is much similar to the foreshock-mainshock-aftershock sequences observed along the spreading rift valley zones. These characteristics help us to support that swarms along the slow spreading mid-Indian Ocean ridges are the result of extensional tectonic activity, leading to the development of the median valley topography, a mechanism similar to that proposed by Bergman and Solomon (1990) for the Mid-Atlantic Ridge.
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References
Bergman E A and Solomon S C 1990 Earthquake swarms on the Mid-Atlantic Ridge: Products of magmatism or extensional tectonis?;J. Geophys. Res. 95 4943–4965
DeMets C, Gordon R G, Argus F and Stein S 1990 Current plate motions;Geophys. J. Inter. 101 425–478
Dziewonski A M, Frazen J E and Woodhouse J H 1984 Centroid moment tensor solutions for July-Sept 1983;Phys. Earth Planet. Inter. 34 1–8
Evernden J F 1969 Precision of epicenters obtained by small numbers of worldwide stations;Bull. Seis. Soc. Am. 59 1365–1398
Fisher R L, Sclater J G and McKenzie D P 1971 Evolution of the Central Indian Ridge, Western Indian Ocean;Geol. Soc. Am. Bull. 82 553–562
Fisher R L, Jantsch M Z and Comer R L 1982 General bathymetric chart of the Ocean (GEBCO) 5th ed. sheet 5.09;Can. Hydrogr. Serv., Ottawa, Ont.
Fisher R L and Sclater J G 1983 Tectonic evolution of the Southwest Indian Ocean since the mid-Cretaceous: Plate motions and stability of the pole of Antarctica/Africa for at least 80 M Yr.;Geophys. J. R. Astr. Soc. 73 553–576
Francis T J G 1968a The detailed seismicity of mid-Ocean ridges;Earth. Planet. Sci. Lett. 4 39–46
Francis T J G 1968b Seismicity of mid-Oceanic ridges and its relation to properties of the upper mantle and crust;Nature (London) 220 899–901
Francis T J G and Porter I T 1971 A statistical study of MidAtlantic Ridge Earthquakes;Geophys. J. R. Astr. Soc. 24 31–50
Hill D P 1977 A model for earthquake swarms;J. Geophys. Res. 82 1347–1352
Huang P Y and Solomon S C 1987 Centroid depths and mechanisms of mid-Ocean ridge earthquakes in the Indian Ocean, Gulf of Aden, and Red Sea;J. Geophys. Res. 92 1361–1382
Klein F W, Einarsson P and Wyss M 1977 The Reykjanes Peninsula, Iceland, earthquake swarm of September 1972 and its tectonic significance;J. Geophys. Res. 82 865–888
Klein F W, Koyanagi R Y, Nakata J S and Tanigawa W R 1987 The seismicity of Kilauea’s magma system;U.S. Geol. Surv. Prof. Pap. 1350 1019–1186
Laughton A S 1975 General bathymetrie charts of the Ocean (GEBCO) 5th ed. sheet. 5.05;Can. Hydrogr. Serv., Ottawa, Ontario
Macdonald K C 1986 The crest of the Mid-Atlantic Ridge: Models for crustal generation processes and tectonics, in:The geology of North America, The Western North Atlantic Region, (ed) P R Vogt and B E Tulchoke, 51–68;Geol. Soc. Am. Volume M, 51–68
Macdonald K C, Fox P J, Perram L J, Eisen M F, Haymon R M, Miller S P, Carbotte S M, Cormier M H and Shor, A N 1988 A new view of the mid-Ocean ridge from the behaviour of ridge axis discontinuities;Nature (London) 335 217–225
McKenzie D P and Sclater J G 1971 The evolution of the Indian Ocean since the Late Cretaceous;Geophys. J. R. Astr. Soc. 25 437–528
Nava F A and Glowacka E 1994 Automatic identification of seismic swarms and other spatio-temporal clustering from catalogs;Computers and Geosciences 20 797–820
Royer J Y, Sclater J G and Sandwell D T 1989 A preliminary tectonic chart of the Indian Ocean;Proc. Indian. Acad. Sci. (Earth Planet. Sci.) 98 7–24
Royer J Y and Chang T 1991 Evidence for relative motions between the Indian and Australian plates during the last 20 m.y from plate tectonic reconstructions: Implications for the deformation of the Indo-Australian plate;J. Geophys. Res. 96 11,779–11,802
Ruegg J C, Lepine J C, Tarantola A and Kasser M 1979 Geodetic measurements of rifting associated with a seismovolcanic crisis in Afar;Geophys. Res. Lett. 6 817–820
Sigurdsson O 1980 Surface deformation of the Krafa fissure swarm in two rifting events;J. Geophys. 47 154–159
Sykes L R 1970 Earthquake swarms and sea-floor spreading;J. Geophys. Res. 75 6598–6611
Wald D J and Wallace T C 1986 A seismically active section of the Southwest Indian Ridge;Geophys. Res. Lett. 13 1003–1006
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Radha Krishna, M., Arora, S.K. Space-time seismicity and earthquake swarms: Certain observations along the slow-spreading mid-Indian Ocean ridges. Proc. Indian Acad. Sci. (Earth Planet Sci.) 107, 161–173 (1998). https://doi.org/10.1007/BF02840467
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DOI: https://doi.org/10.1007/BF02840467