The 1943 Tosya–Ladik earthquake occurred at 01:20 local time on 27 November, near Tosya, Kastamonu Province, in northern Turkey. The earthquake had an estimated moment magnitude of 7.5–7.7 and a maximum felt intensity of XI (Catastrophic) on the MSK-64 scale. Its effects were observed for over 45,000 km2. The earthquake was felt in Trabzon, Isparta, Elazığ, Zonguldak and Yozgat. Damage was seen in Kastamonu, Çankırı, Çorum, Amasya, Samsun, Tokat, Sinop and Ordu. As a result of the earthquake, more than 2,500 were killed and 5,000 were injured.
Tectonic setting
The Anatolian Plate is a small piece of continental plate that is turning counter-clockwise as it heads westward comparative to the Eurasian Plate on the north. The deformation of the plate is facilitated by three important tectonic forces relative to a stable Eurasian Plate: one being the pushing force done by the Arabian Plate below which is heading northward, one being the opposite, pulling force done by the extension in the western part of the plate related to the back-arc extension related with the Hellenic subduction zone, and one being a dragging force done on the Anatolian Plate from the lithosphere under. The southeastern side of the Anatolian Plate is bordered by the East Anatolian Fault, which is home to most of the left-lateral strike-slip displacement on this side of the tectonic plate.
The earthquake occurred on the North Anatolian Fault, which is a fault line around 1500 km long, right-lateral, strike-slip plate boundary fault between the Eurasian Plate and the Anatolian Plate that travels across the northern section of Turkey. Large earthquakes measuring 7+ magnitudes on the North Anatolian fault in the 1900s have ruptured in a migrating sequence from the east towards the west. This pattern indicates a rather strong relation between the fault ruptures and an increased risk of rupture on bordering sections of the fault. Due the latest earthquake in the migrating sequence occurring at the eastern edge of the Marmara Sea, at Izmit, the possible westward continuity of the pattern involves a very important and likely deadly hazard to one of the most populous cities in the world, Istanbul. The migrating large quake pattern suggests that the North Anatolian fault responds to built up stress on the fault by triggering a pulse of strain on a bordering unruptured fault section which drops the strain after exceedance of stress limits. By determining the timing of these earthquakes on the fault, the understanding of these processes resulting in fault rupture can be enhanced. A long, historical record of many surface rupturing earthquakes on this fault documents extensive and destructive damage and casualties on the North Anatolian Fault. The historical records provide precise time-related constraints on many earthquakes over the past 2,000 years. Increasing numbers of paleo-seismic investigations have been undertaken on the fault, and these investigations and studies suggest that the earthquake record is not complete, particularly in the central areas of the fault. Additionally, the record of historical earthquakes provide little spatial constraint on the places that have had a surface rupture.
Earthquake
The earthquake reportedly struck during a cloudy and rainy night, and first started with light shaking which intensified and lasted for around 4 minutes. The residents near the epicenter were awakened by the sound of thunder and humming and saw that they were shaking like a cradle. Shortly after the earthquake the local residents woke up and raced into the streets to see what was going on.
The Tosya-Ladik earthquake ruptured a 280-km-long segment of the North Anatolian fault, from the district of Ilgaz in Çankırı province all the way to Ladik in the Samsun province. The scarps caused by the rupture also had slip of 2-3 meters in some places.