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

342 H. N. Sriuastava and S. K. Das36-2;--200-13-1 1 1 I I I6 5O 700 75" 8oo 85' 9000 SEISMOLOGICAL HEADOUATERSEXISTING SEISMOLOGICAL 00SERVATORIES UNDERNATIONAL NET WORK0 PROPOSED SEISMOLOGICAL 085ERVATORlE5 UNDERNATIONAL NET WORK DURING VI PLAN PERIOD,0 PROPOSED OBSERVATORIES UNDER PROJECT HIMALYAFigure S. Seismological observatories of the India Meteorological Department.It may be worth mentioning that out of 55 stations maintained by IMD, as many as11 stations have been opened during the two year period of 1982-83. It is expectedthat IMD will eventually have a network of 103 permanent stations during thenext few years, so that the epicentral parameters of earthquakes of M >_ 4 may bereliably determined in the Indian region.4. Seismicity Map of the Indian RegionFigure 4 shows the active seismicity of the Himalayan-Burmese-Andaman region,across which the more accepted boundary of the Indian plate extends. The followinginteresting features may be noted:(1) Great earthquakes (M > 8.0) have occurred in 1819, 1897, 1905, 1934, 1941and 1950, i.e. only during the last 175 years. In view of the proximity of the plateboundary, it is unlikely that great earthquakes have not occurred prior to 1800. Itis therefore a limitation of the catalogues in the Indian region making it difficult toreliably assess earthquake risk.