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

The History of Earthquakes in the Northern North Sea 303Figure 3. Macroseismic map for the 1927/1/24 earthquake, illustrating the epicentralconstraints that can be obtained when an event is felt at opposing coastlines.for the post-wax years, which is limited by the biases and high detection thresholds ofearly seismological networks. The most accurate picture of the seismicity, albeit fora short period of 5 years, is that provided by the distribution of events above 2.3 MLbetween 1980 and 1984 (Bungum et al., 1985). This picture, shown in Figure 5,indicates a pattern of seismicity which is consistent with the macroseismic data plotshown in Figure 4.The distribution of seismicity in the northern North Sea requires explanationwithin a regional seismotectonic model. The seismicity of the eastern half of thenorthern North Sea is delineated to the north, west and south by regions generallylacking seismicity (see Figures 4-5). The western boundary of the seismic provinceis itself approximately defined by the Viking Graben, the location of the epicenterof the largest observed earthquake of the northern North Sea region on 24 January