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| Date | July 22, 1967 |
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| Magnitude | 7.1 Ms[1] |
| Depth | < 10Km [2] |
| Epicenter | [3] |
| Countries or regions | Turkey |
| Max. intensity | locally variable |
| Casualties | 86 |
The 1967 Mudurnu earthquake or more correctly, the 1967 Mudurnu Valley earthquake occurred at about 16:57 GMT (18:57 local time) on July 22, 1967, near Mudurnu, Bolu Province, north-western Turkey.[4] The earthquake was one of a series of major and intermediate quakes that have occurred in modern times along the North Anatolian Fault since 1939. [5]
Although the Mudurnu Valley earthquake was relatively strong, there were only 86 fatalities, with 332 people injured. About 5,200 houses were destroyed or damaged beyond repair[6]; some 900 of these were in Adapazari at the far western end of the fault zone, and many collapsed completely as a result of aftershocks.[7]
The surface rupture zone, which was between 1–4 kilometers wide, stretched some 80 kilometers from to Lake Abant (Turkish: Abant Gölu) to Sapanca in an East-West direction, generally following the course of the Mudurnu River until it flows north near Lake Sapanca. The earthquake is named after the river valley, not the town of Mudurnu itself, which is some distance south of the river and outside the rupture zone.
Considering the large magnitude (7.1) and widespread surface rupturing, structural damage to buildings was surprisingly small; variations in damage were related to the materials used and construction method of individual buildings, rather than the proximity to the fault-break.[8] Some villages suffered 70% destruction of property, while others nearby with fault lines running right through them had only a few houses damaged.
A number of small aftershocks occurred, mostly towards the westward end of the fault zone; its eastern end overlapped the rupture zone of a previous 7.1 earthquake (1957 Abant) with a similar epicentre, by about 25Km.[9][10]
The authors of the 1968 Unesco report into the Mudurnu Valley earthquake (see Sources) felt that its intensity was difficult to estimate accurately. In some places an implied level of XII was evident, whereas the vibrational effects were nearer VIII-IX (MM). Although a large number of sites were independently assessed by up to six observers, variations of up to four degrees of the (MM) scale indicated that an accurate figure was practically impossible to gauge.[11]