Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

Historical Seismicity and Earthquake Catalogues for Indian Region 3412.2. Ban galore EarthquakeOn 20 March 1984, an earthquake was reported felt at Bangalore, Mysore inKarnataka and Krishnagiri in Tamil Nadu at about 4 P.M. The earthquake waswidely felt in the peninsular India.Cracks were reported to have developed in old buildings at Bangalore (I = IV toV) but slightly more damage was reported at Kelamangalam (12.6' N, 77.88' E)and Kowthalam (12.58" N, 77.8' E) where intensity was assessed as VI (Iyengar andMeera, 1984). At Kelamangalam and Kowthalam, vertical cracks in the plaster werenoticed in several structures of types A and B. At Kowthalam, light objects suchas utensils overturned in most of the houses. A 2 meter tall papaya tree which hada circular diameter of about 30 cm was uprooted. In one of the houses, portionsof a mud wall collapsed. The damage survey indicated that the epicentre lay inthe village of Kowthalam. The intensity assessed by closer scrutiny of field datasuggests the shock to be of the same order of magnitude as Hyderabad earthquake(1983). The epicentral parameters of this earthquake were as follows: origin time =10h 45m 29.5s (GMT); epicentre = 12' 49.55' N, 77' 26.27' E; h = 21 km; M = 4.5.A perusal of historical records has shown that the city of Bangalore and itsneighbourhood had experienced the following earthquakes: (1) April 1882 - earthquakeseverly felt at Bangalore, also felt at Ootacaumund, Vercerd and Hosur; (2)17 February 1891 - severe shock felt throughout Bangalore district; (3) 7 January1916 - near Bangalore, A4 = 5; and (4) 3 May 1980 - south of Bangalore.Both of the recent earthquakes of Hyderabad (1983) and Bangalore (1984) couldbe associated with northeast-trending lineaments identified from Land Sat imagesand corroborated by the pattern of isoseismals.3. Seismological Network in IndiaThe first seismological station in the country was established at Calcutta (Alipur)on 1 December 1898. During 1898-99, seismic observations were started at Bombay(Colaba) and Kodaikanal using Milne seismographs. After the great Kangraearthquake of 1905, a seismological observatory started functioning at Simla withan Omori-Ewing seismograph. In 1911-12 another instrument for recording verticalcomponents of seismic waves, designed by Wiechert, was installed at Simla. Thiswas moved to Agra in 1929. The observatory was also equipped with a Milne-Shawseismograph. During the 1930s, seismological observatories also started functioningat Dehradun and the Nizamiah Observatory, Hyderabad. In 1941, the seismologicalobservatory at Agra was shifted to Delhi. The number of seismological stations inthe country increased to 8 in 1950, and later rose to 15 in 1960 when more sensitiveinstruments like Benioff, Sprengnether and Wood- Anderson seismographs wereadded. At present, the number of observatories under the National Network ofstations in the country is 35 (Figure 3). The stations at Delhi, Poona, Kodaikanal,and Shillong were equipped with sensitive seismographs with known calibrationcurves during 1962-63 under the World- Wide Standardized Seismograph Network(WWSSN). An observatory with a similar set of instruments was started at theNational Geophysical Research Institute, Hyderbad, in 1968. Prior to this, theGauribidanur array station under the Bhabha Atomic Research Centre was alsoput into operation. 18 stations will be set up under the Department of Science andTechnology project on "Seismicity and Seismotectonics of the Himalayan Region."