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

340 H. N. Srivastava and S. K. Dnsnear Coimbatore, an earthquake of I = IV was reported on 24 June 1865. Similarly,near Ongole, where an earthquake of M = 5.4 occurrecl on 27 March 1967,earthquakes of slightly lesser intensity were reported on 1 September 1869 and later.Two of the felt earthquakes reported in the new catalogue on 10 and 11 Septemberwere the aftershocks of the main event of 1 September but with decreasing intensity.Such a pattern of aftershocks with decreasing trend was characteristic of thetectonic activity of the region, and could be differentiated from swarm-type activitywhich is attributed to local crustal adjustments, as reported from neighbouringregions like Tambaran during 1966. The focal mechanism of the 1967 earthquake(Cliaiiclra, 1977) also supported its association with tectonic features, even thoughtwo possible fault plane solutions could be drawn due to paucity of data.The extract of the new earthquake catalog of peninsular India was presentedduring the IASPEI/Unesco Workshop on Historical Seisniograms, in Tokyo, December1982. Since then, the following earthquakes have occurred of almost similarintensity as reported in tlie historical catalogues.2.1. Hyderabad EarthquakeOn 30 June 1983, an earthquake occurred near Hyderabad which caused minordamage such as cracks in roofs and walls in houses. Some portions of tiled roofarid mud wall collapsed at villages of Kislitpur and Bandainailaram. Shaking wasreported for about 20 seconds in the niesoseismal area which decreased to about 10seconds at Hyderabad arid Secuiiderabad. The earthquake was accompanied by loudsound. The maximum intensity was I = V (M.M.), and field data suggested thatthe epicentre was near Medchal village, about 30 km north of Hyderabad (Rastogiand Chadha, 1984). The shock was felt over an area of 450,000 mi2. The epicentralparameters of this earthquake as determined by IMD are: latitude = 18.07’ N;longitude = 78.43’ E; origin time = Gh 59111 25.9s (GMT); focal depth = shallow;and M = 5.0.About two months prior to the Hyderabad earthquake, IMD had communicatedto the Geological Survey of India Hyderabad the description of an earthquake in1876, based on the new catalogue of earthquakes prepared for peninsular India, andrequested t,hem to get more details from local Gazetteers. Although no additionalinformation could be obtained, the occurrence of the 1983 event was not taken asa surprise because the 1876 event had already been brought to notice, which hadits epicentre near Secunderabad and was of similar intensity. The historical eventof 1876 was described in Times of India as follows:“Felt throughout tlie city, caused general alarm, glass panes broken insoiiie of the houses, a number of sparrows found dead after the earthquake,barracks in coiitoiiiiient area were more or less in an oscillatingcondition for 55 to 60 seconds. Effects in different areas ranged from beingthrown out of bed to as if rocked in a cradle. Punkah wires jingled,doors and windows shook, parrots screamed, dogs barked and men wokeup by the rolling and loud noise accompanying the earthquakes, someprivate bungalows in and out of contonment were damaged, but no largescale destruction or loss of life.”