The 1932 Ierissos earthquake occurred at 19:20 on 26 September. It caused severe damage in Ierissos and the surrounding part of the Chalkidiki peninsula, with 491 casualties reported.

Tectonic setting

The Aegean Sea

Aegean Sea

The Aegean Sea[p] is an elongated embayment of the Mediterranean Sea located between the southern Balkan and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosporus...

 is an area of mainly extensional tectonics

Extensional tectonics

Extensional tectonics is concerned with the structures formed, and the tectonic processes associated with, the stretching of the crust or lithosphere.-Deformation styles:...

 caused by the subduction

Subduction

In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

 of the African Plate

African Plate

The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...

 beneath Aegean Sea Plate

Aegean Sea Plate

The Aegean Sea Plate is a small tectonic plate located in the eastern Mediterranean Sea under southern Greece and far western Turkey. Its southern edge is a subduction zone south of Crete, where the African Plate is being swept under the Aegean Sea Plate...

. In the northwest Aegean, extension on approximately W-E trending extensional faults is accompanied by dextral (right lateral) strike-slip on SW-NE trending faults, and minor sinistral (left lateral) movement on NW-SE trending faults, accommodating the diffuse plate boundary zone between the Eurasian Plate

Eurasian Plate

The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...

 and the Aegean Sea Plate. The earthquake has been attributed to movement on the Stratoni fault, one of the W-E trending faults that shows predominantly dip-slip extension.

Damage

The earthquake destroyed the town of Ierissos and several villages in the surrounding area. 10,000 people were left homeless. The cost of the damage was estimated as 5 million drachmas.

The minor tsunami

Tsunami

A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 caused no damage.

Characteristics

The Stratoni fault was identified as the fault responsible for the 1932 event because of evidence of surface ruptures recorded soon after the earthquake and from the pattern of isoseismals

Isoseismal map

In seismology an isoseismal map is used to show lines of equal felt seismic intensity, generally measured on the Modified Mercalli scale. Such maps help to identify earthquake epicenters, particularly where no instrumental records exist, such as for historical earthquakes...

, which were elongated in a W-E to NW-SE orientation and similarly orientated volume of recently observed seismicity. From the observation of slickensides along exposed fault planes, the movement along the fault is dip-slip extensional with local areas of oblique slip with a component of sinistral (left-lateral) strike-slip. The extension direction is currently oriented north-south but, when the fault was formed, was oriented NNE-SSW, perpendicular to the fault trace, possibly due to subsequent clockwise rotation of the area.

The earthquake was followed by three strong aftershock

Aftershock

An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...

s (M=6.0, 5.7 & 6.2) in the period 26–29 September, and the largest (M6.3) on 11 May of the following year.

A minor tsunami was reported, which was recorded by a temporary tide gauge

Tide gauge

A tide gauge is a device for measuring sea level and detecting tsunamis.Sensors continuously record the height of the water level with respect to a height reference surface close to the geoid...

, giving a maximum height of 1 m. The movement awoke the operator of a dredger, who saw a current spreading up the Strimonas River about an hour after the earthquake.