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The Seismic Activity of the Marmara Sea Region over the Last 2000 Years

Department of Civil Engineering
Imperial College of Science, Technology, and Medicine
Exhibition Rd., London SW7 2BU, U.K.
n.ambraseys{at}ic.ac.uk

View larger version (34K): [in a new window]   Figure 1. Location map with place names mentioned in the text; inset shows study areas: A, Marmara Sea region; B, Marmara Basin.

View larger version (28K): [in a new window]   Figure 2. Summary tectonic map of the Marmara Sea region. Solid and dashed lines correspond to strike-slip and normal faults of Barka and Kadinsky-Cade (1988). Superimposed are the epicenters of earthquakes of MS 5.0 from 1900 to 1999.

View larger version (62K): [in a new window]   Figure 3. Bathymetric and topographic map of the Marmara Sea region. Below sea level, the bathymetry contours with intervals of 200 m are shown as solid lines; the dashed lines are the 50 m and 100 m bathymetric contours. Topography above 200 m is stippled (based on Smith et al., 1995). Location of topographical features mentioned in the text: I, Izmit subbasin; K, Karamürsel subbasin. Large arrows show the year of the event, and small arrows show the probable location of damaging and felt sea wave, respectively.

View larger version (30K): [in a new window]   Figure 4. Map showing epicenters of earthquakes after 1899 and location of epicentral regions of historical events of MS 6.8 for the period 1 to 1899. Locations at sea are inferred from macroseismic observations and fault positions. Earthquakes of MS between 6.8and 7.4 will have ruptured faults 30 to more than 100 km in length. Numbers refer to entries in Table 1. Solid and dashed lines indicate strike-slip and normal faults, respectively, of Barka and Kadinsky-Cade (1988). Solid circles are graded for 6.8 MS < 7.0, 7.0 MS < 7.3, and MS > 7.3.

View larger version (39K): [in a new window]   Figure 5. Plot of magnitude MS from equations (1) shown by thick lines, and MI from equation (6) drawn with thin lines, for intensities III, IV, VI, and VIII. Site distances for equation (1) are epicentral below the graycurve and source distances above it. For equation (6) source distances are epicentral.

View larger version (22K): [in a new window]   Figure 6. Comparison of M estimated by Parsons et al. (2000) (MI solid circles) and by Hubert-Ferrari et al. (2000) (MH solid squares) with MS in this study.

View larger version (37K): [in a new window]   Figure 7. Cumulative seismic moment release in the 420-km-long Marmara Sea region (A) as a function of time for the events listed in Table 1. Total seismic moment released: 3.9 x 1028 dyne cm.

View larger version (43K): [in a new window]   Figure 8. Percentage of the total number of earthquakes per century in the Marmara Sea region in the last 1700 yr.

View larger version (33K): [in a new window]   Figure 9. Cumulative seismic moment release in the 210-km-long Marmara Basin region (B) as a function of time for the events listed in Table 1. Total seismic moment released: 1.8 x 1028 dyne cm.

View larger version (29K): [in a new window]   Figure 10. Variation with time of average slip rate in cm/yr calculated for the Marmara Sea region.

View larger version (28K): [in a new window]   Figure 11. Variation with time of average slip rate in cm/yr calculated for the Marmara Basin region.

View larger version (17K): [in a new window]   Figure 12. Frequency-magnitude distribution. Values of (N/ya) have been normalized to annual rate and unit area of 23,000 km2, that of the Marmara Basin region. 1, crosses: Marmara Sea area, 100 yr; 2, X: Marmara Basin, 100 yr; 3, open circles: Marmara Sea area, 2000 yr; 4, open squares: Marmara Basin, 2000 yr.

View larger version (30K): [in a new window]   Figure 13. Frequency-magnitude distribution for MS 6.8. 1, crosses: Marmara Sea area, 100 yr; 2, X: Marmara Basin, 100 yr; 3, open circles: Marmara Sea area, 2000 yr; 4, open squares: Marmara Basin, 2000 yr.

View larger version (65K): [in a new window]   Figure 14. Distribution of the average seismic moment released (without correction for the missing MS < 6.8) per degree of latitude (84 km) in the last 2000 yr. Seismic moment x 1027 dyne cm. A and B are the lengths of the Marmara Sea region and Marmara Basin, respectively. The moment deficiency in region B is not all that large, and it may be partly due to the large number of missing events of MS < 6.8.