During two distinct earthquakes occurred on March 7, 1867 and October 6, 1944, tsunami waves were also observed at some localities around the Gulf of Edremit, NE Aegean Sea. The first event (M (w) = 6.8) mostly affected the city of Mitilini of Lesvos Island while the Gulf of Edremit-AyvacA +/- k earthquake (M (S) = 6.8) largely affected the northern and eastern coastal areas of the Gulf of Edremit. In 1944 earthquake, numerous surface cracks and water gushes were reported. The coastal neighborhoods of the town of AyvalA +/- k in the east were flooded by tsunami waves. At the WSW extend of the main fault observed on land, which is parallel to the present-day slip vectors, some normal-oblique faults were observed close and subparallel to the northern coast. On the basis of historical documents, reports, interviews, geological setting, field observations and marine seismic reflection data, the 1944 earthquake was not triggered by one of the main fault segments but by a secondary fault or fault group which was described in this study. Depending on the distribution of tensional and compressional forces in the region, which rotates clockwise under the control of the middle strand of the North Anatolian fault, secondary fault groups become important. The moment tensor parameters of such small-size events have been determined and have obtained consistent results with the faults proposed in this study.